Use YangInstanceIdentifier.EMPTY
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / test / java / org / opendaylight / controller / cluster / datastore / ShardTest.java
index 94b9698abf3a06f41527a83e5cec2461b2658266..994c91ca89e318d36d9b032928fb5843004189ca 100644 (file)
+/*
+ * Copyright (c) 2014, 2015 Cisco Systems, Inc. and others.  All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+
 package org.opendaylight.controller.cluster.datastore;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
-import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.inOrder;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.verify;
 import static org.opendaylight.controller.cluster.datastore.DataStoreVersions.CURRENT_VERSION;
 import akka.actor.ActorRef;
-import akka.actor.PoisonPill;
+import akka.actor.ActorSelection;
 import akka.actor.Props;
+import akka.actor.Status.Failure;
 import akka.dispatch.Dispatchers;
 import akka.dispatch.OnComplete;
 import akka.japi.Creator;
-import akka.japi.Procedure;
 import akka.pattern.Patterns;
-import akka.persistence.SnapshotSelectionCriteria;
+import akka.persistence.SaveSnapshotSuccess;
 import akka.testkit.TestActorRef;
 import akka.util.Timeout;
 import com.google.common.base.Function;
-import com.google.common.base.Optional;
-import com.google.common.util.concurrent.CheckedFuture;
+import com.google.common.base.Stopwatch;
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
-import com.google.common.util.concurrent.MoreExecutors;
 import com.google.common.util.concurrent.Uninterruptibles;
-import java.io.IOException;
 import java.util.Collections;
 import java.util.HashSet;
-import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
-import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 import org.mockito.InOrder;
-import org.mockito.invocation.InvocationOnMock;
-import org.mockito.stubbing.Answer;
 import org.opendaylight.controller.cluster.DataPersistenceProvider;
-import org.opendaylight.controller.cluster.datastore.DatastoreContext.Builder;
+import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
+import org.opendaylight.controller.cluster.access.concepts.MemberName;
+import org.opendaylight.controller.cluster.datastore.exceptions.NoShardLeaderException;
 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
+import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardStats;
 import org.opendaylight.controller.cluster.datastore.messages.AbortTransaction;
 import org.opendaylight.controller.cluster.datastore.messages.AbortTransactionReply;
+import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
+import org.opendaylight.controller.cluster.datastore.messages.BatchedModificationsReply;
 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransaction;
 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransactionReply;
 import org.opendaylight.controller.cluster.datastore.messages.CommitTransaction;
 import org.opendaylight.controller.cluster.datastore.messages.CommitTransactionReply;
 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
-import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
+import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
 import org.opendaylight.controller.cluster.datastore.messages.PeerAddressResolved;
+import org.opendaylight.controller.cluster.datastore.messages.ReadData;
+import org.opendaylight.controller.cluster.datastore.messages.ReadDataReply;
+import org.opendaylight.controller.cluster.datastore.messages.ReadyLocalTransaction;
 import org.opendaylight.controller.cluster.datastore.messages.ReadyTransactionReply;
 import org.opendaylight.controller.cluster.datastore.messages.RegisterChangeListener;
 import org.opendaylight.controller.cluster.datastore.messages.RegisterChangeListenerReply;
+import org.opendaylight.controller.cluster.datastore.messages.RegisterDataTreeChangeListener;
+import org.opendaylight.controller.cluster.datastore.messages.RegisterDataTreeChangeListenerReply;
+import org.opendaylight.controller.cluster.datastore.messages.ShardLeaderStateChanged;
 import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContext;
+import org.opendaylight.controller.cluster.datastore.modification.DeleteModification;
 import org.opendaylight.controller.cluster.datastore.modification.MergeModification;
-import org.opendaylight.controller.cluster.datastore.modification.Modification;
-import org.opendaylight.controller.cluster.datastore.modification.ModificationPayload;
 import org.opendaylight.controller.cluster.datastore.modification.MutableCompositeModification;
 import org.opendaylight.controller.cluster.datastore.modification.WriteModification;
-import org.opendaylight.controller.cluster.datastore.node.NormalizedNodeToNodeCodec;
-import org.opendaylight.controller.cluster.datastore.utils.InMemoryJournal;
-import org.opendaylight.controller.cluster.datastore.utils.InMemorySnapshotStore;
 import org.opendaylight.controller.cluster.datastore.utils.MockDataChangeListener;
+import org.opendaylight.controller.cluster.datastore.utils.MockDataTreeChangeListener;
 import org.opendaylight.controller.cluster.datastore.utils.SerializationUtils;
+import org.opendaylight.controller.cluster.notifications.RegisterRoleChangeListener;
+import org.opendaylight.controller.cluster.notifications.RegisterRoleChangeListenerReply;
+import org.opendaylight.controller.cluster.raft.RaftActorContext;
 import org.opendaylight.controller.cluster.raft.ReplicatedLogEntry;
 import org.opendaylight.controller.cluster.raft.ReplicatedLogImplEntry;
 import org.opendaylight.controller.cluster.raft.Snapshot;
-import org.opendaylight.controller.cluster.raft.base.messages.ApplyLogEntries;
-import org.opendaylight.controller.cluster.raft.base.messages.ApplySnapshot;
+import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
-import org.opendaylight.controller.cluster.raft.base.messages.CaptureSnapshot;
 import org.opendaylight.controller.cluster.raft.base.messages.ElectionTimeout;
+import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
-import org.opendaylight.controller.cluster.raft.protobuff.client.messages.CompositeModificationByteStringPayload;
-import org.opendaylight.controller.cluster.raft.protobuff.client.messages.CompositeModificationPayload;
+import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
+import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
+import org.opendaylight.controller.cluster.raft.messages.RequestVote;
+import org.opendaylight.controller.cluster.raft.messages.ServerRemoved;
+import org.opendaylight.controller.cluster.raft.policy.DisableElectionsRaftPolicy;
+import org.opendaylight.controller.cluster.raft.utils.InMemoryJournal;
+import org.opendaylight.controller.cluster.raft.utils.MessageCollectorActor;
 import org.opendaylight.controller.md.cluster.datastore.model.SchemaContextHelper;
 import org.opendaylight.controller.md.cluster.datastore.model.TestModel;
 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataBroker;
-import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeEvent;
-import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeListener;
 import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
-import org.opendaylight.controller.md.sal.dom.store.impl.InMemoryDOMDataStore;
-import org.opendaylight.controller.md.sal.dom.store.impl.InMemoryDOMDataStoreFactory;
-import org.opendaylight.controller.protobuff.messages.common.NormalizedNodeMessages;
-import org.opendaylight.controller.protobuff.messages.transaction.ShardTransactionMessages.CreateTransactionReply;
-import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadTransaction;
-import org.opendaylight.controller.sal.core.spi.data.DOMStoreThreePhaseCommitCohort;
-import org.opendaylight.controller.sal.core.spi.data.DOMStoreWriteTransaction;
+import org.opendaylight.yangtools.util.StringIdentifier;
 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
-import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
-import org.opendaylight.yangtools.yang.data.api.schema.DataContainerChild;
-import org.opendaylight.yangtools.yang.data.api.schema.MapEntryNode;
+import org.opendaylight.yangtools.yang.data.api.schema.ContainerNode;
+import org.opendaylight.yangtools.yang.data.api.schema.MapNode;
 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidateNode;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidateTip;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeModification;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.ModificationType;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
 import org.opendaylight.yangtools.yang.data.impl.schema.ImmutableNodes;
-import org.opendaylight.yangtools.yang.model.api.SchemaContext;
+import org.opendaylight.yangtools.yang.data.impl.schema.builder.impl.ImmutableContainerNodeBuilder;
+import org.opendaylight.yangtools.yang.data.impl.schema.tree.InMemoryDataTreeFactory;
 import scala.concurrent.Await;
 import scala.concurrent.Future;
 import scala.concurrent.duration.FiniteDuration;
 
-public class ShardTest extends AbstractActorTest {
-
-    private static final SchemaContext SCHEMA_CONTEXT = TestModel.createTestContext();
-
-    private static final AtomicInteger NEXT_SHARD_NUM = new AtomicInteger();
-
-    private final ShardIdentifier shardID = ShardIdentifier.builder().memberName("member-1")
-            .shardName("inventory").type("config" + NEXT_SHARD_NUM.getAndIncrement()).build();
-
-    private final Builder dataStoreContextBuilder = DatastoreContext.newBuilder().
-            shardJournalRecoveryLogBatchSize(3).shardSnapshotBatchCount(5000).
-            shardHeartbeatIntervalInMillis(100);
-
-    @Before
-    public void setUp() {
-        Builder newBuilder = DatastoreContext.newBuilder();
-        InMemorySnapshotStore.clear();
-        InMemoryJournal.clear();
-    }
-
-    @After
-    public void tearDown() {
-        InMemorySnapshotStore.clear();
-        InMemoryJournal.clear();
-    }
-
-    private DatastoreContext newDatastoreContext() {
-        return dataStoreContextBuilder.build();
-    }
-
-    private Props newShardProps() {
-        return Shard.props(shardID, Collections.<ShardIdentifier,String>emptyMap(),
-                newDatastoreContext(), SCHEMA_CONTEXT);
-    }
+public class ShardTest extends AbstractShardTest {
+    private static final String DUMMY_DATA = "Dummy data as snapshot sequence number is set to 0 in InMemorySnapshotStore and journal recovery seq number will start from 1";
 
     @Test
     public void testRegisterChangeListener() throws Exception {
         new ShardTestKit(getSystem()) {{
-            TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps(),  "testRegisterChangeListener");
 
             waitUntilLeader(shard);
 
             shard.tell(new UpdateSchemaContext(SchemaContextHelper.full()), ActorRef.noSender());
 
-            MockDataChangeListener listener = new MockDataChangeListener(1);
-            ActorRef dclActor = getSystem().actorOf(DataChangeListener.props(listener),
+            final MockDataChangeListener listener = new MockDataChangeListener(1);
+            final ActorRef dclActor = actorFactory.createActor(DataChangeListener.props(listener),
                     "testRegisterChangeListener-DataChangeListener");
 
             shard.tell(new RegisterChangeListener(TestModel.TEST_PATH,
-                    dclActor.path(), AsyncDataBroker.DataChangeScope.BASE), getRef());
+                    dclActor, AsyncDataBroker.DataChangeScope.BASE, true), getRef());
 
-            RegisterChangeListenerReply reply = expectMsgClass(duration("3 seconds"),
+            final RegisterChangeListenerReply reply = expectMsgClass(duration("3 seconds"),
                     RegisterChangeListenerReply.class);
-            String replyPath = reply.getListenerRegistrationPath().toString();
+            final String replyPath = reply.getListenerRegistrationPath().toString();
             assertTrue("Incorrect reply path: " + replyPath, replyPath.matches(
                     "akka:\\/\\/test\\/user\\/testRegisterChangeListener\\/\\$.*"));
 
-            YangInstanceIdentifier path = TestModel.TEST_PATH;
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
             writeToStore(shard, path, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
 
             listener.waitForChangeEvents(path);
-
-            dclActor.tell(PoisonPill.getInstance(), ActorRef.noSender());
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
     }
 
@@ -190,15 +169,18 @@ public class ShardTest extends AbstractActorTest {
             // ElectionTimeout with the sending of the RegisterChangeListener message.
             final CountDownLatch onFirstElectionTimeout = new CountDownLatch(1);
             final CountDownLatch onChangeListenerRegistered = new CountDownLatch(1);
-            Creator<Shard> creator = new Creator<Shard>() {
+            final Creator<Shard> creator = new Creator<Shard>() {
                 boolean firstElectionTimeout = true;
 
                 @Override
                 public Shard create() throws Exception {
-                    return new Shard(shardID, Collections.<ShardIdentifier,String>emptyMap(),
-                            newDatastoreContext(), SCHEMA_CONTEXT) {
+                    // Use a non persistent provider because this test actually invokes persist on the journal
+                    // this will cause all other messages to not be queued properly after that.
+                    // The basic issue is that you cannot use TestActorRef with a persistent actor (at least when
+                    // it does do a persist)
+                    return new Shard(newShardBuilder()) {
                         @Override
-                        public void onReceiveCommand(final Object message) throws Exception {
+                        public void handleCommand(final Object message) {
                             if(message instanceof ElectionTimeout && firstElectionTimeout) {
                                 // Got the first ElectionTimeout. We don't forward it to the
                                 // base Shard yet until we've sent the RegisterChangeListener
@@ -221,42 +203,42 @@ public class ShardTest extends AbstractActorTest {
 
                                 onFirstElectionTimeout.countDown();
                             } else {
-                                super.onReceiveCommand(message);
+                                super.handleCommand(message);
                             }
                         }
                     };
                 }
             };
 
-            MockDataChangeListener listener = new MockDataChangeListener(1);
-            ActorRef dclActor = getSystem().actorOf(DataChangeListener.props(listener),
+            setupInMemorySnapshotStore();
+
+            final MockDataChangeListener listener = new MockDataChangeListener(1);
+            final ActorRef dclActor = actorFactory.createActor(DataChangeListener.props(listener),
                     "testRegisterChangeListenerWhenNotLeaderInitially-DataChangeListener");
 
-            TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
-                    Props.create(new DelegatingShardCreator(creator)),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    Props.create(new DelegatingShardCreator(creator)).withDispatcher(Dispatchers.DefaultDispatcherId()),
                     "testRegisterChangeListenerWhenNotLeaderInitially");
 
-            // Write initial data into the in-memory store.
-            YangInstanceIdentifier path = TestModel.TEST_PATH;
-            writeToStore(shard, path, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
 
             // Wait until the shard receives the first ElectionTimeout message.
             assertEquals("Got first ElectionTimeout", true,
                     onFirstElectionTimeout.await(5, TimeUnit.SECONDS));
 
             // Now send the RegisterChangeListener and wait for the reply.
-            shard.tell(new RegisterChangeListener(path, dclActor.path(),
-                    AsyncDataBroker.DataChangeScope.SUBTREE), getRef());
+            shard.tell(new RegisterChangeListener(path, dclActor,
+                    AsyncDataBroker.DataChangeScope.SUBTREE, false), getRef());
 
-            RegisterChangeListenerReply reply = expectMsgClass(duration("5 seconds"),
+            final RegisterChangeListenerReply reply = expectMsgClass(duration("5 seconds"),
                     RegisterChangeListenerReply.class);
             assertNotNull("getListenerRegistrationPath", reply.getListenerRegistrationPath());
 
             // Sanity check - verify the shard is not the leader yet.
-            shard.tell(new FindLeader(), getRef());
-            FindLeaderReply findLeadeReply =
+            shard.tell(FindLeader.INSTANCE, getRef());
+            final FindLeaderReply findLeadeReply =
                     expectMsgClass(duration("5 seconds"), FindLeaderReply.class);
-            assertNull("Expected the shard not to be the leader", findLeadeReply.getLeaderActor());
+            assertFalse("Expected the shard not to be the leader", findLeadeReply.getLeaderActor().isPresent());
 
             // Signal the onChangeListenerRegistered latch to tell the thread above to proceed
             // with the election process.
@@ -265,440 +247,264 @@ public class ShardTest extends AbstractActorTest {
             // Wait for the shard to become the leader and notify our listener with the existing
             // data in the store.
             listener.waitForChangeEvents(path);
-
-            dclActor.tell(PoisonPill.getInstance(), ActorRef.noSender());
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
     }
 
     @Test
-    public void testCreateTransaction(){
+    public void testRegisterDataTreeChangeListener() throws Exception {
         new ShardTestKit(getSystem()) {{
-            ActorRef shard = getSystem().actorOf(newShardProps(), "testCreateTransaction");
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps(), "testRegisterDataTreeChangeListener");
 
             waitUntilLeader(shard);
 
-            shard.tell(new UpdateSchemaContext(TestModel.createTestContext()), getRef());
-
-            shard.tell(new CreateTransaction("txn-1",
-                    TransactionProxy.TransactionType.READ_ONLY.ordinal() ).toSerializable(), getRef());
-
-            CreateTransactionReply reply = expectMsgClass(duration("3 seconds"),
-                    CreateTransactionReply.class);
-
-            String path = reply.getTransactionActorPath().toString();
-            assertTrue("Unexpected transaction path " + path,
-                    path.contains("akka://test/user/testCreateTransaction/shard-txn-1"));
-
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
-        }};
-    }
-
-    @Test
-    public void testCreateTransactionOnChain(){
-        new ShardTestKit(getSystem()) {{
-            final ActorRef shard = getSystem().actorOf(newShardProps(), "testCreateTransactionOnChain");
+            shard.tell(new UpdateSchemaContext(SchemaContextHelper.full()), ActorRef.noSender());
 
-            waitUntilLeader(shard);
+            final MockDataTreeChangeListener listener = new MockDataTreeChangeListener(1);
+            final ActorRef dclActor = actorFactory.createActor(DataTreeChangeListenerActor.props(listener),
+                    "testRegisterDataTreeChangeListener-DataTreeChangeListener");
 
-            shard.tell(new CreateTransaction("txn-1",
-                    TransactionProxy.TransactionType.READ_ONLY.ordinal() , "foobar").toSerializable(),
-                    getRef());
+            shard.tell(new RegisterDataTreeChangeListener(TestModel.TEST_PATH, dclActor, false), getRef());
 
-            CreateTransactionReply reply = expectMsgClass(duration("3 seconds"),
-                    CreateTransactionReply.class);
+            final RegisterDataTreeChangeListenerReply reply = expectMsgClass(duration("3 seconds"),
+                    RegisterDataTreeChangeListenerReply.class);
+            final String replyPath = reply.getListenerRegistrationPath().toString();
+            assertTrue("Incorrect reply path: " + replyPath, replyPath.matches(
+                    "akka:\\/\\/test\\/user\\/testRegisterDataTreeChangeListener\\/\\$.*"));
 
-            String path = reply.getTransactionActorPath().toString();
-            assertTrue("Unexpected transaction path " + path,
-                    path.contains("akka://test/user/testCreateTransactionOnChain/shard-txn-1"));
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
+            writeToStore(shard, path, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
 
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            listener.waitForChangeEvents();
         }};
     }
 
     @SuppressWarnings("serial")
     @Test
-    public void testPeerAddressResolved() throws Exception {
+    public void testDataTreeChangeListenerNotifiedWhenNotTheLeaderOnRegistration() throws Exception {
         new ShardTestKit(getSystem()) {{
-            final CountDownLatch recoveryComplete = new CountDownLatch(1);
-            class TestShard extends Shard {
-                TestShard() {
-                    super(shardID, Collections.<ShardIdentifier, String>singletonMap(shardID, null),
-                            newDatastoreContext(), SCHEMA_CONTEXT);
-                }
-
-                Map<String, String> getPeerAddresses() {
-                    return getRaftActorContext().getPeerAddresses();
-                }
+            final CountDownLatch onFirstElectionTimeout = new CountDownLatch(1);
+            final CountDownLatch onChangeListenerRegistered = new CountDownLatch(1);
+            final Creator<Shard> creator = new Creator<Shard>() {
+                boolean firstElectionTimeout = true;
 
                 @Override
-                protected void onRecoveryComplete() {
-                    try {
-                        super.onRecoveryComplete();
-                    } finally {
-                        recoveryComplete.countDown();
-                    }
-                }
-            }
-
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
-                    Props.create(new DelegatingShardCreator(new Creator<Shard>() {
+                public Shard create() throws Exception {
+                    return new Shard(newShardBuilder()) {
                         @Override
-                        public TestShard create() throws Exception {
-                            return new TestShard();
-                        }
-                    })), "testPeerAddressResolved");
-
-            //waitUntilLeader(shard);
-            assertEquals("Recovery complete", true,
-                    Uninterruptibles.awaitUninterruptibly(recoveryComplete, 5, TimeUnit.SECONDS));
-
-            String address = "akka://foobar";
-            shard.underlyingActor().onReceiveCommand(new PeerAddressResolved(shardID, address));
+                        public void handleCommand(final Object message) {
+                            if(message instanceof ElectionTimeout && firstElectionTimeout) {
+                                firstElectionTimeout = false;
+                                final ActorRef self = getSelf();
+                                new Thread() {
+                                    @Override
+                                    public void run() {
+                                        Uninterruptibles.awaitUninterruptibly(
+                                                onChangeListenerRegistered, 5, TimeUnit.SECONDS);
+                                        self.tell(message, self);
+                                    }
+                                }.start();
 
-            assertEquals("getPeerAddresses", address,
-                    ((TestShard)shard.underlyingActor()).getPeerAddresses().get(shardID.toString()));
+                                onFirstElectionTimeout.countDown();
+                            } else {
+                                super.handleCommand(message);
+                            }
+                        }
+                    };
+                }
+            };
 
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
-        }};
-    }
+            setupInMemorySnapshotStore();
 
-    @Test
-    public void testApplySnapshot() throws Exception {
-        TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(),
-                "testApplySnapshot");
+            final MockDataTreeChangeListener listener = new MockDataTreeChangeListener(1);
+            final ActorRef dclActor = actorFactory.createActor(DataTreeChangeListenerActor.props(listener),
+                    "testDataTreeChangeListenerNotifiedWhenNotTheLeaderOnRegistration-DataChangeListener");
 
-        InMemoryDOMDataStore store = new InMemoryDOMDataStore("OPER", MoreExecutors.sameThreadExecutor());
-        store.onGlobalContextUpdated(SCHEMA_CONTEXT);
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    Props.create(new DelegatingShardCreator(creator)).withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testDataTreeChangeListenerNotifiedWhenNotTheLeaderOnRegistration");
 
-        writeToStore(store, TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
 
-        YangInstanceIdentifier root = YangInstanceIdentifier.builder().build();
-        NormalizedNode<?,?> expected = readStore(store, root);
+            assertEquals("Got first ElectionTimeout", true,
+                onFirstElectionTimeout.await(5, TimeUnit.SECONDS));
 
-        ApplySnapshot applySnapshot = new ApplySnapshot(Snapshot.create(
-                SerializationUtils.serializeNormalizedNode(expected),
-                Collections.<ReplicatedLogEntry>emptyList(), 1, 2, 3, 4));
+            shard.tell(new RegisterDataTreeChangeListener(path, dclActor, false), getRef());
+            final RegisterDataTreeChangeListenerReply reply = expectMsgClass(duration("5 seconds"),
+                RegisterDataTreeChangeListenerReply.class);
+            assertNotNull("getListenerRegistratioznPath", reply.getListenerRegistrationPath());
 
-        shard.underlyingActor().onReceiveCommand(applySnapshot);
+            shard.tell(FindLeader.INSTANCE, getRef());
+            final FindLeaderReply findLeadeReply =
+                    expectMsgClass(duration("5 seconds"), FindLeaderReply.class);
+            assertFalse("Expected the shard not to be the leader", findLeadeReply.getLeaderActor().isPresent());
 
-        NormalizedNode<?,?> actual = readStore(shard, root);
 
-        assertEquals("Root node", expected, actual);
+            onChangeListenerRegistered.countDown();
 
-        shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            // TODO: investigate why we do not receive data chage events
+            listener.waitForChangeEvents();
+        }};
     }
 
     @Test
-    public void testApplyHelium2VersionSnapshot() throws Exception {
-        TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(),
-                "testApplySnapshot");
+    public void testCreateTransaction(){
+        new ShardTestKit(getSystem()) {{
+            final ActorRef shard = actorFactory.createActor(newShardProps(), "testCreateTransaction");
 
-        NormalizedNodeToNodeCodec codec = new NormalizedNodeToNodeCodec(SCHEMA_CONTEXT);
+            waitUntilLeader(shard);
 
-        InMemoryDOMDataStore store = new InMemoryDOMDataStore("OPER", MoreExecutors.sameThreadExecutor());
-        store.onGlobalContextUpdated(SCHEMA_CONTEXT);
+            shard.tell(new UpdateSchemaContext(TestModel.createTestContext()), getRef());
 
-        writeToStore(store, TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
+            shard.tell(new CreateTransaction("txn-1", TransactionType.READ_ONLY.ordinal(), null,
+                    DataStoreVersions.CURRENT_VERSION).toSerializable(), getRef());
 
-        YangInstanceIdentifier root = YangInstanceIdentifier.builder().build();
-        NormalizedNode<?,?> expected = readStore(store, root);
+            final CreateTransactionReply reply = expectMsgClass(duration("3 seconds"),
+                    CreateTransactionReply.class);
 
-        NormalizedNodeMessages.Container encode = codec.encode(expected);
+            final String path = reply.getTransactionPath().toString();
+            assertTrue("Unexpected transaction path " + path,
+                    path.contains("akka://test/user/testCreateTransaction/shard-txn-1"));
+        }};
+    }
 
-        ApplySnapshot applySnapshot = new ApplySnapshot(Snapshot.create(
-                encode.getNormalizedNode().toByteString().toByteArray(),
-                Collections.<ReplicatedLogEntry>emptyList(), 1, 2, 3, 4));
+    @Test
+    public void testCreateTransactionOnChain(){
+        new ShardTestKit(getSystem()) {{
+            final ActorRef shard = actorFactory.createActor(newShardProps(), "testCreateTransactionOnChain");
 
-        shard.underlyingActor().onReceiveCommand(applySnapshot);
+            waitUntilLeader(shard);
 
-        NormalizedNode<?,?> actual = readStore(shard, root);
+            shard.tell(new CreateTransaction("txn-1",TransactionType.READ_ONLY.ordinal(), "foobar",
+                    DataStoreVersions.CURRENT_VERSION).toSerializable(), getRef());
 
-        assertEquals("Root node", expected, actual);
+            final CreateTransactionReply reply = expectMsgClass(duration("3 seconds"),
+                    CreateTransactionReply.class);
 
-        shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            final String path = reply.getTransactionPath().toString();
+            assertTrue("Unexpected transaction path " + path,
+                    path.contains("akka://test/user/testCreateTransactionOnChain/shard-txn-1"));
+        }};
     }
 
     @Test
-    public void testApplyState() throws Exception {
+    public void testPeerAddressResolved() throws Exception {
+        new ShardTestKit(getSystem()) {{
+            ShardIdentifier peerID = ShardIdentifier.create("inventory", MemberName.forName("member-2"), "config");
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(newShardBuilder().
+                    peerAddresses(Collections.<String, String>singletonMap(peerID.toString(), null)).props().
+                        withDispatcher(Dispatchers.DefaultDispatcherId()), "testPeerAddressResolved");
 
-        TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(), "testApplyState");
+            final String address = "akka://foobar";
+            shard.tell(new PeerAddressResolved(peerID.toString(), address), ActorRef.noSender());
 
-        NormalizedNode<?, ?> node = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+            shard.tell(GetOnDemandRaftState.INSTANCE, getRef());
+            OnDemandRaftState state = expectMsgClass(OnDemandRaftState.class);
+            assertEquals("getPeerAddress", address, state.getPeerAddresses().get(peerID.toString()));
+        }};
+    }
 
-        ApplyState applyState = new ApplyState(null, "test", new ReplicatedLogImplEntry(1, 2,
-                newModificationPayload(new WriteModification(TestModel.TEST_PATH, node))));
+    @Test
+    public void testApplySnapshot() throws Exception {
 
-        shard.underlyingActor().onReceiveCommand(applyState);
+        final TestActorRef<Shard> shard = actorFactory.createTestActor(newShardProps(), "testApplySnapshot");
 
-        NormalizedNode<?,?> actual = readStore(shard, TestModel.TEST_PATH);
-        assertEquals("Applied state", node, actual);
+        ShardTestKit.waitUntilLeader(shard);
 
-        shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
-    }
+        final DataTree store = InMemoryDataTreeFactory.getInstance().create(TreeType.OPERATIONAL);
+        store.setSchemaContext(SCHEMA_CONTEXT);
 
-    @Test
-    public void testApplyStateLegacy() throws Exception {
+        final ContainerNode container = ImmutableContainerNodeBuilder.create().withNodeIdentifier(
+                new YangInstanceIdentifier.NodeIdentifier(TestModel.TEST_QNAME)).
+                    withChild(ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).addChild(
+                        ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 1)).build()).build();
 
-        TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(), "testApplyStateLegacy");
+        writeToStore(store, TestModel.TEST_PATH, container);
 
-        NormalizedNode<?, ?> node = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+        final YangInstanceIdentifier root = YangInstanceIdentifier.EMPTY;
+        final NormalizedNode<?,?> expected = readStore(store, root);
 
-        ApplyState applyState = new ApplyState(null, "test", new ReplicatedLogImplEntry(1, 2,
-                newLegacyByteStringPayload(new WriteModification(TestModel.TEST_PATH, node))));
+        final Snapshot snapshot = Snapshot.create(SerializationUtils.serializeNormalizedNode(expected),
+                Collections.<ReplicatedLogEntry>emptyList(), 1, 2, 3, 4);
 
-        shard.underlyingActor().onReceiveCommand(applyState);
+        shard.underlyingActor().getRaftActorSnapshotCohort().applySnapshot(snapshot.getState());
 
-        NormalizedNode<?,?> actual = readStore(shard, TestModel.TEST_PATH);
-        assertEquals("Applied state", node, actual);
+        final NormalizedNode<?,?> actual = readStore(shard, root);
 
-        shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        assertEquals("Root node", expected, actual);
     }
 
     @Test
-    public void testRecovery() throws Exception {
-
-        // Set up the InMemorySnapshotStore.
-
-        InMemoryDOMDataStore testStore = InMemoryDOMDataStoreFactory.create("Test", null, null);
-        testStore.onGlobalContextUpdated(SCHEMA_CONTEXT);
-
-        writeToStore(testStore, TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
+    public void testApplyState() throws Exception {
+        final TestActorRef<Shard> shard = actorFactory.createTestActor(newShardProps(), "testApplyState");
 
-        NormalizedNode<?, ?> root = readStore(testStore, YangInstanceIdentifier.builder().build());
+        ShardTestKit.waitUntilLeader(shard);
 
-        InMemorySnapshotStore.addSnapshot(shardID.toString(), Snapshot.create(
-                SerializationUtils.serializeNormalizedNode(root),
-                Collections.<ReplicatedLogEntry>emptyList(), 0, 1, -1, -1));
+        final DataTree source = setupInMemorySnapshotStore();
+        final DataTreeModification writeMod = source.takeSnapshot().newModification();
+        ContainerNode node = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+        writeMod.write(TestModel.TEST_PATH, node);
+        writeMod.ready();
 
-        // Set up the InMemoryJournal.
+        final ApplyState applyState = new ApplyState(null, new StringIdentifier("test"),
+            new ReplicatedLogImplEntry(1, 2, payloadForModification(source, writeMod)));
 
-        InMemoryJournal.addEntry(shardID.toString(), 0, new ReplicatedLogImplEntry(0, 1, newLegacyPayload(
-                  new WriteModification(TestModel.OUTER_LIST_PATH,
-                          ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build()))));
+        shard.tell(applyState, shard);
 
-        int nListEntries = 16;
-        Set<Integer> listEntryKeys = new HashSet<>();
+        Stopwatch sw = Stopwatch.createStarted();
+        while(sw.elapsed(TimeUnit.SECONDS) <= 5) {
+            Uninterruptibles.sleepUninterruptibly(75, TimeUnit.MILLISECONDS);
 
-        // Add some ModificationPayload entries
-        for(int i = 1; i <= nListEntries; i++) {
-            listEntryKeys.add(Integer.valueOf(i));
-            YangInstanceIdentifier path = YangInstanceIdentifier.builder(TestModel.OUTER_LIST_PATH)
-                    .nodeWithKey(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, i).build();
-            Modification mod = new MergeModification(path,
-                    ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, i));
-            InMemoryJournal.addEntry(shardID.toString(), i, new ReplicatedLogImplEntry(i, 1,
-                    newModificationPayload(mod)));
+            final NormalizedNode<?,?> actual = readStore(shard, TestModel.TEST_PATH);
+            if(actual != null) {
+                assertEquals("Applied state", node, actual);
+                return;
+            }
         }
 
-        InMemoryJournal.addEntry(shardID.toString(), nListEntries + 1,
-                new ApplyLogEntries(nListEntries));
-
-        testRecovery(listEntryKeys);
+        fail("State was not applied");
     }
 
     @Test
-    public void testHelium2VersionRecovery() throws Exception {
-
+    public void testDataTreeCandidateRecovery() throws Exception {
         // Set up the InMemorySnapshotStore.
+        final DataTree source = setupInMemorySnapshotStore();
 
-        InMemoryDOMDataStore testStore = InMemoryDOMDataStoreFactory.create("Test", null, null);
-        testStore.onGlobalContextUpdated(SCHEMA_CONTEXT);
-
-        writeToStore(testStore, TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
-
-        NormalizedNode<?, ?> root = readStore(testStore, YangInstanceIdentifier.builder().build());
-
-        InMemorySnapshotStore.addSnapshot(shardID.toString(), Snapshot.create(
-                new NormalizedNodeToNodeCodec(SCHEMA_CONTEXT).encode(root).
-                                getNormalizedNode().toByteString().toByteArray(),
-                                Collections.<ReplicatedLogEntry>emptyList(), 0, 1, -1, -1));
+        final DataTreeModification writeMod = source.takeSnapshot().newModification();
+        writeMod.write(TestModel.OUTER_LIST_PATH, ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build());
+        writeMod.ready();
+        InMemoryJournal.addEntry(shardID.toString(), 0, DUMMY_DATA);
 
         // Set up the InMemoryJournal.
+        InMemoryJournal.addEntry(shardID.toString(), 1, new ReplicatedLogImplEntry(0, 1, payloadForModification(source, writeMod)));
 
-        InMemoryJournal.addEntry(shardID.toString(), 0, new ReplicatedLogImplEntry(0, 1, newLegacyPayload(
-                  new WriteModification(TestModel.OUTER_LIST_PATH,
-                          ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build()))));
+        final int nListEntries = 16;
+        final Set<Integer> listEntryKeys = new HashSet<>();
 
-        int nListEntries = 16;
-        Set<Integer> listEntryKeys = new HashSet<>();
-        int i = 1;
-
-        // Add some CompositeModificationPayload entries
-        for(; i <= 8; i++) {
+        // Add some ModificationPayload entries
+        for (int i = 1; i <= nListEntries; i++) {
             listEntryKeys.add(Integer.valueOf(i));
-            YangInstanceIdentifier path = YangInstanceIdentifier.builder(TestModel.OUTER_LIST_PATH)
-                    .nodeWithKey(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, i).build();
-            Modification mod = new MergeModification(path,
-                    ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, i));
-            InMemoryJournal.addEntry(shardID.toString(), i, new ReplicatedLogImplEntry(i, 1,
-                    newLegacyPayload(mod)));
-        }
 
-        // Add some CompositeModificationByteStringPayload entries
-        for(; i <= nListEntries; i++) {
-            listEntryKeys.add(Integer.valueOf(i));
-            YangInstanceIdentifier path = YangInstanceIdentifier.builder(TestModel.OUTER_LIST_PATH)
+            final YangInstanceIdentifier path = YangInstanceIdentifier.builder(TestModel.OUTER_LIST_PATH)
                     .nodeWithKey(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, i).build();
-            Modification mod = new MergeModification(path,
-                    ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, i));
-            InMemoryJournal.addEntry(shardID.toString(), i, new ReplicatedLogImplEntry(i, 1,
-                    newLegacyByteStringPayload(mod)));
-        }
-
-        InMemoryJournal.addEntry(shardID.toString(), nListEntries + 1, new ApplyLogEntries(nListEntries));
-
-        testRecovery(listEntryKeys);
-    }
-
-    private void testRecovery(Set<Integer> listEntryKeys) throws Exception {
-        // Create the actor and wait for recovery complete.
-
-        int nListEntries = listEntryKeys.size();
-
-        final CountDownLatch recoveryComplete = new CountDownLatch(1);
-
-        @SuppressWarnings("serial")
-        Creator<Shard> creator = new Creator<Shard>() {
-            @Override
-            public Shard create() throws Exception {
-                return new Shard(shardID, Collections.<ShardIdentifier,String>emptyMap(),
-                        newDatastoreContext(), SCHEMA_CONTEXT) {
-                    @Override
-                    protected void onRecoveryComplete() {
-                        try {
-                            super.onRecoveryComplete();
-                        } finally {
-                            recoveryComplete.countDown();
-                        }
-                    }
-                };
-            }
-        };
-
-        TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
-                Props.create(new DelegatingShardCreator(creator)), "testRecovery");
-
-        assertEquals("Recovery complete", true, recoveryComplete.await(5, TimeUnit.SECONDS));
-
-        // Verify data in the data store.
-
-        NormalizedNode<?, ?> outerList = readStore(shard, TestModel.OUTER_LIST_PATH);
-        assertNotNull(TestModel.OUTER_LIST_QNAME.getLocalName() + " not found", outerList);
-        assertTrue(TestModel.OUTER_LIST_QNAME.getLocalName() + " value is not Iterable",
-                outerList.getValue() instanceof Iterable);
-        for(Object entry: (Iterable<?>) outerList.getValue()) {
-            assertTrue(TestModel.OUTER_LIST_QNAME.getLocalName() + " entry is not MapEntryNode",
-                    entry instanceof MapEntryNode);
-            MapEntryNode mapEntry = (MapEntryNode)entry;
-            Optional<DataContainerChild<? extends PathArgument, ?>> idLeaf =
-                    mapEntry.getChild(new YangInstanceIdentifier.NodeIdentifier(TestModel.ID_QNAME));
-            assertTrue("Missing leaf " + TestModel.ID_QNAME.getLocalName(), idLeaf.isPresent());
-            Object value = idLeaf.get().getValue();
-            assertTrue("Unexpected value for leaf "+ TestModel.ID_QNAME.getLocalName() + ": " + value,
-                    listEntryKeys.remove(value));
-        }
-
-        if(!listEntryKeys.isEmpty()) {
-            fail("Missing " + TestModel.OUTER_LIST_QNAME.getLocalName() + " entries with keys: " +
-                    listEntryKeys);
-        }
-
-        assertEquals("Last log index", nListEntries,
-                shard.underlyingActor().getShardMBean().getLastLogIndex());
-        assertEquals("Commit index", nListEntries,
-                shard.underlyingActor().getShardMBean().getCommitIndex());
-        assertEquals("Last applied", nListEntries,
-                shard.underlyingActor().getShardMBean().getLastApplied());
-
-        shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
-    }
-
-    private CompositeModificationPayload newLegacyPayload(final Modification... mods) {
-        MutableCompositeModification compMod = new MutableCompositeModification();
-        for(Modification mod: mods) {
-            compMod.addModification(mod);
-        }
-
-        return new CompositeModificationPayload(compMod.toSerializable());
-    }
-
-    private CompositeModificationByteStringPayload newLegacyByteStringPayload(final Modification... mods) {
-        MutableCompositeModification compMod = new MutableCompositeModification();
-        for(Modification mod: mods) {
-            compMod.addModification(mod);
-        }
-
-        return new CompositeModificationByteStringPayload(compMod.toSerializable());
-    }
 
-    private ModificationPayload newModificationPayload(final Modification... mods) throws IOException {
-        MutableCompositeModification compMod = new MutableCompositeModification();
-        for(Modification mod: mods) {
-            compMod.addModification(mod);
+            final DataTreeModification mod = source.takeSnapshot().newModification();
+            mod.merge(path, ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, i));
+            mod.ready();
+            InMemoryJournal.addEntry(shardID.toString(), i+1, new ReplicatedLogImplEntry(i, 1,
+                payloadForModification(source, mod)));
         }
 
-        return new ModificationPayload(compMod);
-    }
-
-    private DOMStoreThreePhaseCommitCohort setupMockWriteTransaction(final String cohortName,
-            final InMemoryDOMDataStore dataStore, final YangInstanceIdentifier path, final NormalizedNode<?, ?> data,
-            final MutableCompositeModification modification) {
-        return setupMockWriteTransaction(cohortName, dataStore, path, data, modification, null);
-    }
-
-    private DOMStoreThreePhaseCommitCohort setupMockWriteTransaction(final String cohortName,
-            final InMemoryDOMDataStore dataStore, final YangInstanceIdentifier path, final NormalizedNode<?, ?> data,
-            final MutableCompositeModification modification,
-            final Function<DOMStoreThreePhaseCommitCohort,ListenableFuture<Void>> preCommit) {
-
-        DOMStoreWriteTransaction tx = dataStore.newWriteOnlyTransaction();
-        tx.write(path, data);
-        final DOMStoreThreePhaseCommitCohort realCohort = tx.ready();
-        DOMStoreThreePhaseCommitCohort cohort = mock(DOMStoreThreePhaseCommitCohort.class, cohortName);
-
-        doAnswer(new Answer<ListenableFuture<Boolean>>() {
-            @Override
-            public ListenableFuture<Boolean> answer(final InvocationOnMock invocation) {
-                return realCohort.canCommit();
-            }
-        }).when(cohort).canCommit();
-
-        doAnswer(new Answer<ListenableFuture<Void>>() {
-            @Override
-            public ListenableFuture<Void> answer(final InvocationOnMock invocation) throws Throwable {
-                if(preCommit != null) {
-                    return preCommit.apply(realCohort);
-                } else {
-                    return realCohort.preCommit();
-                }
-            }
-        }).when(cohort).preCommit();
-
-        doAnswer(new Answer<ListenableFuture<Void>>() {
-            @Override
-            public ListenableFuture<Void> answer(final InvocationOnMock invocation) throws Throwable {
-                return realCohort.commit();
-            }
-        }).when(cohort).commit();
-
-        doAnswer(new Answer<ListenableFuture<Void>>() {
-            @Override
-            public ListenableFuture<Void> answer(final InvocationOnMock invocation) throws Throwable {
-                return realCohort.abort();
-            }
-        }).when(cohort).abort();
-
-        modification.addModification(new WriteModification(path, data));
+        InMemoryJournal.addEntry(shardID.toString(), nListEntries + 2,
+            new ApplyJournalEntries(nListEntries));
 
-        return cohort;
+        testRecovery(listEntryKeys);
     }
 
-    @SuppressWarnings({ "unchecked" })
     @Test
     public void testConcurrentThreePhaseCommits() throws Throwable {
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
                     "testConcurrentThreePhaseCommits");
 
@@ -706,72 +512,64 @@ public class ShardTest extends AbstractActorTest {
 
             // Setup 3 simulated transactions with mock cohorts backed by real cohorts.
 
-            InMemoryDOMDataStore dataStore = shard.underlyingActor().getDataStore();
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
 
-            String transactionID1 = "tx1";
-            MutableCompositeModification modification1 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort1 = setupMockWriteTransaction("cohort1", dataStore,
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification1 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort1 = setupMockWriteTransaction("cohort1", dataStore,
                     TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME), modification1);
 
-            String transactionID2 = "tx2";
-            MutableCompositeModification modification2 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort2 = setupMockWriteTransaction("cohort2", dataStore,
+            final String transactionID2 = "tx2";
+            final MutableCompositeModification modification2 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort2 = setupMockWriteTransaction("cohort2", dataStore,
                     TestModel.OUTER_LIST_PATH,
                     ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build(),
                     modification2);
 
-            String transactionID3 = "tx3";
-            MutableCompositeModification modification3 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort3 = setupMockWriteTransaction("cohort3", dataStore,
+            final String transactionID3 = "tx3";
+            final MutableCompositeModification modification3 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort3 = setupMockWriteTransaction("cohort3", dataStore,
                     YangInstanceIdentifier.builder(TestModel.OUTER_LIST_PATH)
                         .nodeWithKey(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 1).build(),
                     ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 1),
                     modification3);
 
-            long timeoutSec = 5;
+            final long timeoutSec = 5;
             final FiniteDuration duration = FiniteDuration.create(timeoutSec, TimeUnit.SECONDS);
             final Timeout timeout = new Timeout(duration);
 
-            // Simulate the ForwardedReadyTransaction message for the first Tx that would be sent
-            // by the ShardTransaction.
-
-            shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
-                    cohort1, modification1, true), getRef());
-            ReadyTransactionReply readyReply = ReadyTransactionReply.fromSerializable(
-                    expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS));
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort1, transactionID1, modification1), getRef());
+            final ReadyTransactionReply readyReply = ReadyTransactionReply.fromSerializable(
+                    expectMsgClass(duration, ReadyTransactionReply.class));
             assertEquals("Cohort path", shard.path().toString(), readyReply.getCohortPath());
 
             // Send the CanCommitTransaction message for the first Tx.
 
-            shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
-                    expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(duration, CanCommitTransactionReply.class));
             assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
-            // Send the ForwardedReadyTransaction for the next 2 Tx's.
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort2, transactionID2, modification2), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
-            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
-
-            shard.tell(new ForwardedReadyTransaction(transactionID3, CURRENT_VERSION,
-                    cohort3, modification3, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort3, transactionID3, modification3), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             // Send the CanCommitTransaction message for the next 2 Tx's. These should get queued and
             // processed after the first Tx completes.
 
-            Future<Object> canCommitFuture1 = Patterns.ask(shard,
-                    new CanCommitTransaction(transactionID2).toSerializable(), timeout);
+            final Future<Object> canCommitFuture1 = Patterns.ask(shard,
+                    new CanCommitTransaction(transactionID2, CURRENT_VERSION).toSerializable(), timeout);
 
-            Future<Object> canCommitFuture2 = Patterns.ask(shard,
-                    new CanCommitTransaction(transactionID3).toSerializable(), timeout);
+            final Future<Object> canCommitFuture2 = Patterns.ask(shard,
+                    new CanCommitTransaction(transactionID3, CURRENT_VERSION).toSerializable(), timeout);
 
             // Send the CommitTransaction message for the first Tx. After it completes, it should
             // trigger the 2nd Tx to proceed which should in turn then trigger the 3rd.
 
-            shard.tell(new CommitTransaction(transactionID1).toSerializable(), getRef());
-            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(new CommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.class);
 
             // Wait for the next 2 Tx's to complete.
 
@@ -793,7 +591,7 @@ public class ShardTest extends AbstractActorTest {
                         try {
                             assertEquals("Commit response type", expRespType, resp.getClass());
                             onSuccess(resp);
-                        } catch (Exception e) {
+                        } catch (final Exception e) {
                             caughtEx.set(e);
                         }
                     }
@@ -805,7 +603,7 @@ public class ShardTest extends AbstractActorTest {
 
             class OnCommitFutureComplete extends OnFutureComplete {
                 OnCommitFutureComplete() {
-                    super(CommitTransactionReply.SERIALIZABLE_CLASS);
+                    super(CommitTransactionReply.class);
                 }
 
                 @Override
@@ -819,18 +617,18 @@ public class ShardTest extends AbstractActorTest {
                 private final String transactionID;
 
                 OnCanCommitFutureComplete(final String transactionID) {
-                    super(CanCommitTransactionReply.SERIALIZABLE_CLASS);
+                    super(CanCommitTransactionReply.class);
                     this.transactionID = transactionID;
                 }
 
                 @Override
                 void onSuccess(final Object resp) throws Exception {
-                    CanCommitTransactionReply canCommitReply =
+                    final CanCommitTransactionReply canCommitReply =
                             CanCommitTransactionReply.fromSerializable(resp);
                     assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
-                    Future<Object> commitFuture = Patterns.ask(shard,
-                            new CommitTransaction(transactionID).toSerializable(), timeout);
+                    final Future<Object> commitFuture = Patterns.ask(shard,
+                            new CommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), timeout);
                     commitFuture.onComplete(new OnCommitFutureComplete(), getSystem().dispatcher());
                 }
             }
@@ -841,7 +639,7 @@ public class ShardTest extends AbstractActorTest {
             canCommitFuture2.onComplete(new OnCanCommitFutureComplete(transactionID3),
                     getSystem().dispatcher());
 
-            boolean done = commitLatch.await(timeoutSec, TimeUnit.SECONDS);
+            final boolean done = commitLatch.await(timeoutSec, TimeUnit.SECONDS);
 
             if(caughtEx.get() != null) {
                 throw caughtEx.get();
@@ -849,7 +647,7 @@ public class ShardTest extends AbstractActorTest {
 
             assertEquals("Commits complete", true, done);
 
-            InOrder inOrder = inOrder(cohort1, cohort2, cohort3);
+            final InOrder inOrder = inOrder(cohort1, cohort2, cohort3);
             inOrder.verify(cohort1).canCommit();
             inOrder.verify(cohort1).preCommit();
             inOrder.verify(cohort1).commit();
@@ -862,321 +660,1014 @@ public class ShardTest extends AbstractActorTest {
 
             // Verify data in the data store.
 
-            NormalizedNode<?, ?> outerList = readStore(shard, TestModel.OUTER_LIST_PATH);
-            assertNotNull(TestModel.OUTER_LIST_QNAME.getLocalName() + " not found", outerList);
-            assertTrue(TestModel.OUTER_LIST_QNAME.getLocalName() + " value is not Iterable",
-                    outerList.getValue() instanceof Iterable);
-            Object entry = ((Iterable<Object>)outerList.getValue()).iterator().next();
-            assertTrue(TestModel.OUTER_LIST_QNAME.getLocalName() + " entry is not MapEntryNode",
-                       entry instanceof MapEntryNode);
-            MapEntryNode mapEntry = (MapEntryNode)entry;
-            Optional<DataContainerChild<? extends PathArgument, ?>> idLeaf =
-                    mapEntry.getChild(new YangInstanceIdentifier.NodeIdentifier(TestModel.ID_QNAME));
-            assertTrue("Missing leaf " + TestModel.ID_QNAME.getLocalName(), idLeaf.isPresent());
-            assertEquals(TestModel.ID_QNAME.getLocalName() + " value", 1, idLeaf.get().getValue());
-
-            verifyLastLogIndex(shard, 2);
-
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
-        }};
-    }
-
-    private void verifyLastLogIndex(TestActorRef<Shard> shard, long expectedValue) {
-        for(int i = 0; i < 20 * 5; i++) {
-            long lastLogIndex = shard.underlyingActor().getShardMBean().getLastLogIndex();
-            if(lastLogIndex == expectedValue) {
-                break;
-            }
-            Uninterruptibles.sleepUninterruptibly(50, TimeUnit.MILLISECONDS);
-        }
+            verifyOuterListEntry(shard, 1);
 
-        assertEquals("Last log index", expectedValue, shard.underlyingActor().getShardMBean().getLastLogIndex());
+            verifyLastApplied(shard, 2);
+        }};
     }
 
     @Test
-    public void testCommitWithPersistenceDisabled() throws Throwable {
-        dataStoreContextBuilder.persistent(false);
+    public void testBatchedModificationsWithNoCommitOnReady() throws Throwable {
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testCommitPhaseFailure");
+                    "testBatchedModificationsWithNoCommitOnReady");
 
             waitUntilLeader(shard);
 
-            InMemoryDOMDataStore dataStore = shard.underlyingActor().getDataStore();
+            final String transactionID = "tx";
+            final FiniteDuration duration = duration("5 seconds");
 
-            // Setup a simulated transactions with a mock cohort.
+            final AtomicReference<ShardDataTreeCohort> mockCohort = new AtomicReference<>();
+            final ShardCommitCoordinator.CohortDecorator cohortDecorator = (txID, actual) -> {
+                if(mockCohort.get() == null) {
+                    mockCohort.set(createDelegatingMockCohort("cohort", actual));
+                }
 
-            String transactionID = "tx";
-            MutableCompositeModification modification = new MutableCompositeModification();
-            NormalizedNode<?, ?> containerNode = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
-            DOMStoreThreePhaseCommitCohort cohort = setupMockWriteTransaction("cohort", dataStore,
-                    TestModel.TEST_PATH, containerNode, modification);
+                return mockCohort.get();
+            };
+
+            shard.underlyingActor().getCommitCoordinator().setCohortDecorator(cohortDecorator);
 
-            FiniteDuration duration = duration("5 seconds");
+            // Send a BatchedModifications to start a transaction.
 
-            // Simulate the ForwardedReadyTransaction messages that would be sent
-            // by the ShardTransaction.
+            shard.tell(newBatchedModifications(transactionID, TestModel.TEST_PATH,
+                    ImmutableNodes.containerNode(TestModel.TEST_QNAME), false, false, 1), getRef());
+            expectMsgClass(duration, BatchedModificationsReply.class);
 
-            shard.tell(new ForwardedReadyTransaction(transactionID, CURRENT_VERSION,
-                    cohort, modification, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            // Send a couple more BatchedModifications.
+
+            shard.tell(newBatchedModifications(transactionID, TestModel.OUTER_LIST_PATH,
+                    ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build(), false, false, 2), getRef());
+            expectMsgClass(duration, BatchedModificationsReply.class);
+
+            shard.tell(newBatchedModifications(transactionID, YangInstanceIdentifier.builder(
+                    TestModel.OUTER_LIST_PATH).nodeWithKey(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 1).build(),
+                    ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 1), true, false, 3), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             // Send the CanCommitTransaction message.
 
-            shard.tell(new CanCommitTransaction(transactionID).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
-                    expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            shard.tell(new CanCommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(duration, CanCommitTransactionReply.class));
             assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
             // Send the CanCommitTransaction message.
 
-            shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
-            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(new CommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.class);
 
-            InOrder inOrder = inOrder(cohort);
-            inOrder.verify(cohort).canCommit();
-            inOrder.verify(cohort).preCommit();
-            inOrder.verify(cohort).commit();
+            final InOrder inOrder = inOrder(mockCohort.get());
+            inOrder.verify(mockCohort.get()).canCommit();
+            inOrder.verify(mockCohort.get()).preCommit();
+            inOrder.verify(mockCohort.get()).commit();
 
-            NormalizedNode<?, ?> actualNode = readStore(shard, TestModel.TEST_PATH);
-            assertEquals(TestModel.TEST_QNAME.getLocalName(), containerNode, actualNode);
+            // Verify data in the data store.
 
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            verifyOuterListEntry(shard, 1);
         }};
     }
 
     @Test
-    public void testCommitPhaseFailure() throws Throwable {
+    public void testBatchedModificationsWithCommitOnReady() throws Throwable {
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testCommitPhaseFailure");
+                    "testBatchedModificationsWithCommitOnReady");
 
             waitUntilLeader(shard);
 
-            // Setup 2 simulated transactions with mock cohorts. The first one fails in the
-            // commit phase.
+            final String transactionID = "tx";
+            final FiniteDuration duration = duration("5 seconds");
 
-            String transactionID1 = "tx1";
-            MutableCompositeModification modification1 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort1 = mock(DOMStoreThreePhaseCommitCohort.class, "cohort1");
-            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort1).canCommit();
-            doReturn(Futures.immediateFuture(null)).when(cohort1).preCommit();
-            doReturn(Futures.immediateFailedFuture(new IllegalStateException("mock"))).when(cohort1).commit();
+            final AtomicReference<ShardDataTreeCohort> mockCohort = new AtomicReference<>();
+            final ShardCommitCoordinator.CohortDecorator cohortDecorator = (txID, actual) -> {
+                if(mockCohort.get() == null) {
+                    mockCohort.set(createDelegatingMockCohort("cohort", actual));
+                }
 
-            String transactionID2 = "tx2";
-            MutableCompositeModification modification2 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort2 = mock(DOMStoreThreePhaseCommitCohort.class, "cohort2");
-            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort2).canCommit();
+                return mockCohort.get();
+            };
 
-            FiniteDuration duration = duration("5 seconds");
-            final Timeout timeout = new Timeout(duration);
+            shard.underlyingActor().getCommitCoordinator().setCohortDecorator(cohortDecorator);
 
-            // Simulate the ForwardedReadyTransaction messages that would be sent
-            // by the ShardTransaction.
+            // Send a BatchedModifications to start a transaction.
 
-            shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
-                    cohort1, modification1, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(newBatchedModifications(transactionID, TestModel.TEST_PATH,
+                    ImmutableNodes.containerNode(TestModel.TEST_QNAME), false, false, 1), getRef());
+            expectMsgClass(duration, BatchedModificationsReply.class);
 
-            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            // Send a couple more BatchedModifications.
 
-            // Send the CanCommitTransaction message for the first Tx.
+            shard.tell(newBatchedModifications(transactionID, TestModel.OUTER_LIST_PATH,
+                ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build(), false, false, 2), getRef());
+            expectMsgClass(duration, BatchedModificationsReply.class);
 
-            shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
-                    expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
-            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+            shard.tell(newBatchedModifications(transactionID, YangInstanceIdentifier.builder(
+                    TestModel.OUTER_LIST_PATH).nodeWithKey(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 1).build(),
+                ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 1), true, true, 3), getRef());
 
-            // Send the CanCommitTransaction message for the 2nd Tx. This should get queued and
-            // processed after the first Tx completes.
+            expectMsgClass(duration, CommitTransactionReply.class);
 
-            Future<Object> canCommitFuture = Patterns.ask(shard,
-                    new CanCommitTransaction(transactionID2).toSerializable(), timeout);
+            final InOrder inOrder = inOrder(mockCohort.get());
+            inOrder.verify(mockCohort.get()).canCommit();
+            inOrder.verify(mockCohort.get()).preCommit();
+            inOrder.verify(mockCohort.get()).commit();
 
-            // Send the CommitTransaction message for the first Tx. This should send back an error
-            // and trigger the 2nd Tx to proceed.
+            // Verify data in the data store.
 
-            shard.tell(new CommitTransaction(transactionID1).toSerializable(), getRef());
-            expectMsgClass(duration, akka.actor.Status.Failure.class);
+            verifyOuterListEntry(shard, 1);
+        }};
+    }
 
-            // Wait for the 2nd Tx to complete the canCommit phase.
+    @Test(expected=IllegalStateException.class)
+    public void testBatchedModificationsReadyWithIncorrectTotalMessageCount() throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testBatchedModificationsReadyWithIncorrectTotalMessageCount");
 
-            final CountDownLatch latch = new CountDownLatch(1);
-            canCommitFuture.onComplete(new OnComplete<Object>() {
-                @Override
-                public void onComplete(final Throwable t, final Object resp) {
-                    latch.countDown();
-                }
-            }, getSystem().dispatcher());
+            waitUntilLeader(shard);
 
-            assertEquals("2nd CanCommit complete", true, latch.await(5, TimeUnit.SECONDS));
+            final String transactionID = "tx1";
+            final BatchedModifications batched = new BatchedModifications(transactionID, DataStoreVersions.CURRENT_VERSION, null);
+            batched.setReady(true);
+            batched.setTotalMessagesSent(2);
 
-            InOrder inOrder = inOrder(cohort1, cohort2);
-            inOrder.verify(cohort1).canCommit();
-            inOrder.verify(cohort1).preCommit();
-            inOrder.verify(cohort1).commit();
-            inOrder.verify(cohort2).canCommit();
+            shard.tell(batched, getRef());
 
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            final Failure failure = expectMsgClass(duration("5 seconds"), akka.actor.Status.Failure.class);
+
+            if(failure != null) {
+                throw failure.cause();
+            }
         }};
     }
 
     @Test
-    public void testPreCommitPhaseFailure() throws Throwable {
+    public void testBatchedModificationsWithOperationFailure() throws Throwable {
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testPreCommitPhaseFailure");
+                    "testBatchedModificationsWithOperationFailure");
 
             waitUntilLeader(shard);
 
-            String transactionID = "tx1";
-            MutableCompositeModification modification = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort = mock(DOMStoreThreePhaseCommitCohort.class, "cohort1");
-            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).canCommit();
-            doReturn(Futures.immediateFailedFuture(new IllegalStateException("mock"))).when(cohort).preCommit();
-
-            FiniteDuration duration = duration("5 seconds");
+            // Test merge with invalid data. An exception should occur when the merge is applied. Note that
+            // write will not validate the children for performance reasons.
 
-            // Simulate the ForwardedReadyTransaction messages that would be sent
-            // by the ShardTransaction.
-
-            shard.tell(new ForwardedReadyTransaction(transactionID, CURRENT_VERSION,
-                    cohort, modification, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            String transactionID = "tx1";
 
-            // Send the CanCommitTransaction message.
+            ContainerNode invalidData = ImmutableContainerNodeBuilder.create().withNodeIdentifier(
+                    new YangInstanceIdentifier.NodeIdentifier(TestModel.TEST_QNAME)).
+                        withChild(ImmutableNodes.leafNode(TestModel.JUNK_QNAME, "junk")).build();
 
-            shard.tell(new CanCommitTransaction(transactionID).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
-                    expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
-            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+            BatchedModifications batched = new BatchedModifications(transactionID, CURRENT_VERSION, null);
+            batched.addModification(new MergeModification(TestModel.TEST_PATH, invalidData));
+            shard.tell(batched, getRef());
+            Failure failure = expectMsgClass(duration("5 seconds"), akka.actor.Status.Failure.class);
 
-            // Send the CommitTransaction message. This should send back an error
-            // for preCommit failure.
+            Throwable cause = failure.cause();
 
-            shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
-            expectMsgClass(duration, akka.actor.Status.Failure.class);
+            batched = new BatchedModifications(transactionID, DataStoreVersions.CURRENT_VERSION, null);
+            batched.setReady(true);
+            batched.setTotalMessagesSent(2);
 
-            InOrder inOrder = inOrder(cohort);
-            inOrder.verify(cohort).canCommit();
-            inOrder.verify(cohort).preCommit();
+            shard.tell(batched, getRef());
 
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            failure = expectMsgClass(duration("5 seconds"), akka.actor.Status.Failure.class);
+            assertEquals("Failure cause", cause, failure.cause());
         }};
     }
 
     @Test
-    public void testCanCommitPhaseFailure() throws Throwable {
+    public void testBatchedModificationsOnTransactionChain() throws Throwable {
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testCanCommitPhaseFailure");
+                    "testBatchedModificationsOnTransactionChain");
 
             waitUntilLeader(shard);
 
+            final String transactionChainID = "txChain";
+            final String transactionID1 = "tx1";
+            final String transactionID2 = "tx2";
+
             final FiniteDuration duration = duration("5 seconds");
 
-            String transactionID = "tx1";
-            MutableCompositeModification modification = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort = mock(DOMStoreThreePhaseCommitCohort.class, "cohort1");
+            // Send a BatchedModifications to start a chained write transaction and ready it.
+
+            final ContainerNode containerNode = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
+            shard.tell(newBatchedModifications(transactionID1, transactionChainID, path,
+                    containerNode, true, false, 1), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // Create a read Tx on the same chain.
+
+            shard.tell(new CreateTransaction(transactionID2, TransactionType.READ_ONLY.ordinal(),
+                    transactionChainID, DataStoreVersions.CURRENT_VERSION).toSerializable(), getRef());
+
+            final CreateTransactionReply createReply = expectMsgClass(duration("3 seconds"), CreateTransactionReply.class);
+
+            getSystem().actorSelection(createReply.getTransactionPath()).tell(
+                    new ReadData(path, DataStoreVersions.CURRENT_VERSION), getRef());
+            final ReadDataReply readReply = expectMsgClass(duration("3 seconds"), ReadDataReply.class);
+            assertEquals("Read node", containerNode, readReply.getNormalizedNode());
+
+            // Commit the write transaction.
+
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(duration, CanCommitTransactionReply.class));
+            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+            shard.tell(new CommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.class);
+
+            // Verify data in the data store.
+
+            final NormalizedNode<?, ?> actualNode = readStore(shard, path);
+            assertEquals("Stored node", containerNode, actualNode);
+        }};
+    }
+
+    @Test
+    public void testOnBatchedModificationsWhenNotLeader() {
+        final AtomicBoolean overrideLeaderCalls = new AtomicBoolean();
+        new ShardTestKit(getSystem()) {{
+            final Creator<Shard> creator = new Creator<Shard>() {
+                private static final long serialVersionUID = 1L;
+
+                @Override
+                public Shard create() throws Exception {
+                    return new Shard(newShardBuilder()) {
+                        @Override
+                        protected boolean isLeader() {
+                            return overrideLeaderCalls.get() ? false : super.isLeader();
+                        }
+
+                        @Override
+                        protected ActorSelection getLeader() {
+                            return overrideLeaderCalls.get() ? getSystem().actorSelection(getRef().path()) :
+                                super.getLeader();
+                        }
+                    };
+                }
+            };
+
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    Props.create(new DelegatingShardCreator(creator)), "testOnBatchedModificationsWhenNotLeader");
+
+            waitUntilLeader(shard);
+
+            overrideLeaderCalls.set(true);
+
+            final BatchedModifications batched = new BatchedModifications("tx", DataStoreVersions.CURRENT_VERSION, "");
+
+            shard.tell(batched, ActorRef.noSender());
+
+            expectMsgEquals(batched);
+        }};
+    }
+
+    @Test
+    public void testTransactionMessagesWithNoLeader() {
+        new ShardTestKit(getSystem()) {{
+            dataStoreContextBuilder.customRaftPolicyImplementation(DisableElectionsRaftPolicy.class.getName()).
+                shardHeartbeatIntervalInMillis(50).shardElectionTimeoutFactor(1);
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testTransactionMessagesWithNoLeader");
+
+            waitUntilNoLeader(shard);
+
+            shard.tell(new BatchedModifications("tx", DataStoreVersions.CURRENT_VERSION, ""), getRef());
+            Failure failure = expectMsgClass(Failure.class);
+            assertEquals("Failure cause type", NoShardLeaderException.class, failure.cause().getClass());
+
+            shard.tell(prepareForwardedReadyTransaction(mock(ShardDataTreeCohort.class), "tx",
+                    DataStoreVersions.CURRENT_VERSION, true), getRef());
+            failure = expectMsgClass(Failure.class);
+            assertEquals("Failure cause type", NoShardLeaderException.class, failure.cause().getClass());
+
+            shard.tell(new ReadyLocalTransaction("tx", mock(DataTreeModification.class), true), getRef());
+            failure = expectMsgClass(Failure.class);
+            assertEquals("Failure cause type", NoShardLeaderException.class, failure.cause().getClass());
+        }};
+    }
+
+    @Test
+    public void testReadyWithReadWriteImmediateCommit() throws Exception{
+        testReadyWithImmediateCommit(true);
+    }
+
+    @Test
+    public void testReadyWithWriteOnlyImmediateCommit() throws Exception{
+        testReadyWithImmediateCommit(false);
+    }
+
+    private void testReadyWithImmediateCommit(final boolean readWrite) throws Exception{
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testReadyWithImmediateCommit-" + readWrite);
+
+            waitUntilLeader(shard);
+
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
+
+            final String transactionID = "tx1";
+            final MutableCompositeModification modification = new MutableCompositeModification();
+            final NormalizedNode<?, ?> containerNode = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+            final ShardDataTreeCohort cohort = setupMockWriteTransaction("cohort", dataStore,
+                    TestModel.TEST_PATH, containerNode, modification);
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID, modification, true), getRef());
+
+            expectMsgClass(duration, CommitTransactionReply.class);
+
+            final InOrder inOrder = inOrder(cohort);
+            inOrder.verify(cohort).canCommit();
+            inOrder.verify(cohort).preCommit();
+            inOrder.verify(cohort).commit();
+
+            final NormalizedNode<?, ?> actualNode = readStore(shard, TestModel.TEST_PATH);
+            assertEquals(TestModel.TEST_QNAME.getLocalName(), containerNode, actualNode);
+        }};
+    }
+
+    @Test
+    public void testReadyLocalTransactionWithImmediateCommit() throws Exception{
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testReadyLocalTransactionWithImmediateCommit");
+
+            waitUntilLeader(shard);
+
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
+
+            final DataTreeModification modification = dataStore.newModification();
+
+            final ContainerNode writeData = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+            new WriteModification(TestModel.TEST_PATH, writeData).apply(modification);
+            final MapNode mergeData = ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build();
+            new MergeModification(TestModel.OUTER_LIST_PATH, mergeData).apply(modification);
+
+            final String txId = "tx1";
+            modification.ready();
+            final ReadyLocalTransaction readyMessage = new ReadyLocalTransaction(txId, modification, true);
+
+            shard.tell(readyMessage, getRef());
+
+            expectMsgClass(CommitTransactionReply.class);
+
+            final NormalizedNode<?, ?> actualNode = readStore(shard, TestModel.OUTER_LIST_PATH);
+            assertEquals(TestModel.OUTER_LIST_QNAME.getLocalName(), mergeData, actualNode);
+        }};
+    }
+
+    @Test
+    public void testReadyLocalTransactionWithThreePhaseCommit() throws Exception{
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testReadyLocalTransactionWithThreePhaseCommit");
+
+            waitUntilLeader(shard);
+
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
+
+            final DataTreeModification modification = dataStore.newModification();
+
+            final ContainerNode writeData = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+            new WriteModification(TestModel.TEST_PATH, writeData).apply(modification);
+            final MapNode mergeData = ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build();
+            new MergeModification(TestModel.OUTER_LIST_PATH, mergeData).apply(modification);
+
+            final String txId = "tx1";
+                modification.ready();
+            final ReadyLocalTransaction readyMessage = new ReadyLocalTransaction(txId, modification, false);
+
+            shard.tell(readyMessage, getRef());
+
+            expectMsgClass(ReadyTransactionReply.class);
+
+            // Send the CanCommitTransaction message.
+
+            shard.tell(new CanCommitTransaction(txId, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(CanCommitTransactionReply.class));
+            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+            // Send the CanCommitTransaction message.
+
+            shard.tell(new CommitTransaction(txId, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(CommitTransactionReply.class);
+
+            final NormalizedNode<?, ?> actualNode = readStore(shard, TestModel.OUTER_LIST_PATH);
+            assertEquals(TestModel.OUTER_LIST_QNAME.getLocalName(), mergeData, actualNode);
+        }};
+    }
+
+    @Test
+    public void testReadWriteCommitWithPersistenceDisabled() throws Throwable {
+        testCommitWithPersistenceDisabled(true);
+    }
+
+    @Test
+    public void testWriteOnlyCommitWithPersistenceDisabled() throws Throwable {
+        testCommitWithPersistenceDisabled(true);
+    }
+
+    private void testCommitWithPersistenceDisabled(final boolean readWrite) throws Throwable {
+        dataStoreContextBuilder.persistent(false);
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testCommitWithPersistenceDisabled-" + readWrite);
+
+            waitUntilLeader(shard);
+
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
+
+            // Setup a simulated transactions with a mock cohort.
+
+            final String transactionID = "tx";
+            final MutableCompositeModification modification = new MutableCompositeModification();
+            final NormalizedNode<?, ?> containerNode = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+            final ShardDataTreeCohort cohort = setupMockWriteTransaction("cohort", dataStore,
+                TestModel.TEST_PATH, containerNode, modification);
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID, modification), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // Send the CanCommitTransaction message.
+
+            shard.tell(new CanCommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(duration, CanCommitTransactionReply.class));
+            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+            // Send the CanCommitTransaction message.
+
+            shard.tell(new CommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.class);
+
+            final InOrder inOrder = inOrder(cohort);
+            inOrder.verify(cohort).canCommit();
+            inOrder.verify(cohort).preCommit();
+            inOrder.verify(cohort).commit();
+
+            final NormalizedNode<?, ?> actualNode = readStore(shard, TestModel.TEST_PATH);
+            assertEquals(TestModel.TEST_QNAME.getLocalName(), containerNode, actualNode);
+        }};
+    }
+
+    @Test
+    public void testReadWriteCommitWhenTransactionHasNoModifications() {
+        testCommitWhenTransactionHasNoModifications(true);
+    }
+
+    @Test
+    public void testWriteOnlyCommitWhenTransactionHasNoModifications() {
+        testCommitWhenTransactionHasNoModifications(false);
+    }
+
+    private void testCommitWhenTransactionHasNoModifications(final boolean readWrite){
+        // Note that persistence is enabled which would normally result in the entry getting written to the journal
+        // but here that need not happen
+        new ShardTestKit(getSystem()) {
+            {
+                final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                        newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                        "testCommitWhenTransactionHasNoModifications-" + readWrite);
+
+                waitUntilLeader(shard);
+
+                final String transactionID = "tx1";
+                final MutableCompositeModification modification = new MutableCompositeModification();
+                final ShardDataTreeCohort cohort = mock(ShardDataTreeCohort.class, "cohort1");
+                doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).canCommit();
+                doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).preCommit();
+                doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).commit();
+                doReturn(mockUnmodifiedCandidate("cohort1-candidate")).when(cohort).getCandidate();
+
+                final FiniteDuration duration = duration("5 seconds");
+
+                shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID, modification), getRef());
+                expectMsgClass(duration, ReadyTransactionReply.class);
+
+                // Send the CanCommitTransaction message.
+
+                shard.tell(new CanCommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+                final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                        expectMsgClass(duration, CanCommitTransactionReply.class));
+                assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+                shard.tell(new CommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+                expectMsgClass(duration, CommitTransactionReply.class);
+
+                final InOrder inOrder = inOrder(cohort);
+                inOrder.verify(cohort).canCommit();
+                inOrder.verify(cohort).preCommit();
+                inOrder.verify(cohort).commit();
+
+                shard.tell(Shard.GET_SHARD_MBEAN_MESSAGE, getRef());
+                final ShardStats shardStats = expectMsgClass(duration, ShardStats.class);
+
+                // Use MBean for verification
+                // Committed transaction count should increase as usual
+                assertEquals(1,shardStats.getCommittedTransactionsCount());
+
+                // Commit index should not advance because this does not go into the journal
+                assertEquals(-1, shardStats.getCommitIndex());
+            }
+        };
+    }
+
+    @Test
+    public void testReadWriteCommitWhenTransactionHasModifications() {
+        testCommitWhenTransactionHasModifications(true);
+    }
+
+    @Test
+    public void testWriteOnlyCommitWhenTransactionHasModifications() {
+        testCommitWhenTransactionHasModifications(false);
+    }
+
+    private void testCommitWhenTransactionHasModifications(final boolean readWrite){
+        new ShardTestKit(getSystem()) {
+            {
+                final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                        newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                        "testCommitWhenTransactionHasModifications-" + readWrite);
+
+                waitUntilLeader(shard);
+
+                final String transactionID = "tx1";
+                final MutableCompositeModification modification = new MutableCompositeModification();
+                modification.addModification(new DeleteModification(YangInstanceIdentifier.EMPTY));
+                final ShardDataTreeCohort cohort = mock(ShardDataTreeCohort.class, "cohort1");
+                doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).canCommit();
+                doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).preCommit();
+                doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).commit();
+                doReturn(mockCandidate("cohort1-candidate")).when(cohort).getCandidate();
+
+                final FiniteDuration duration = duration("5 seconds");
+
+                shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID, modification), getRef());
+                expectMsgClass(duration, ReadyTransactionReply.class);
+
+                // Send the CanCommitTransaction message.
+
+                shard.tell(new CanCommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+                final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                        expectMsgClass(duration, CanCommitTransactionReply.class));
+                assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+                shard.tell(new CommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+                expectMsgClass(duration, CommitTransactionReply.class);
+
+                final InOrder inOrder = inOrder(cohort);
+                inOrder.verify(cohort).canCommit();
+                inOrder.verify(cohort).preCommit();
+                inOrder.verify(cohort).commit();
+
+                shard.tell(Shard.GET_SHARD_MBEAN_MESSAGE, getRef());
+                final ShardStats shardStats = expectMsgClass(duration, ShardStats.class);
+
+                // Use MBean for verification
+                // Committed transaction count should increase as usual
+                assertEquals(1, shardStats.getCommittedTransactionsCount());
+
+                // Commit index should advance as we do not have an empty modification
+                assertEquals(0, shardStats.getCommitIndex());
+            }
+        };
+    }
+
+    @Test
+    public void testCommitPhaseFailure() throws Throwable {
+        testCommitPhaseFailure(true);
+        testCommitPhaseFailure(false);
+    }
+
+    private void testCommitPhaseFailure(final boolean readWrite) throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testCommitPhaseFailure-" + readWrite);
+
+            waitUntilLeader(shard);
+
+            // Setup 2 simulated transactions with mock cohorts. The first one fails in the
+            // commit phase.
+
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification1 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort1 = mock(ShardDataTreeCohort.class, "cohort1");
+            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort1).canCommit();
+            doReturn(Futures.immediateFuture(null)).when(cohort1).preCommit();
+            doReturn(Futures.immediateFailedFuture(new RuntimeException("mock"))).when(cohort1).commit();
+            doReturn(mockCandidate("cohort1-candidate")).when(cohort1).getCandidate();
+
+            final String transactionID2 = "tx2";
+            final MutableCompositeModification modification2 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort2 = mock(ShardDataTreeCohort.class, "cohort2");
+            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort2).canCommit();
+
+            final FiniteDuration duration = duration("5 seconds");
+            final Timeout timeout = new Timeout(duration);
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort1, transactionID1, modification1), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort2, transactionID2, modification2), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // Send the CanCommitTransaction message for the first Tx.
+
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(duration, CanCommitTransactionReply.class));
+            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+            // Send the CanCommitTransaction message for the 2nd Tx. This should get queued and
+            // processed after the first Tx completes.
+
+            final Future<Object> canCommitFuture = Patterns.ask(shard,
+                    new CanCommitTransaction(transactionID2, CURRENT_VERSION).toSerializable(), timeout);
+
+            // Send the CommitTransaction message for the first Tx. This should send back an error
+            // and trigger the 2nd Tx to proceed.
+
+            shard.tell(new CommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, akka.actor.Status.Failure.class);
+
+            // Wait for the 2nd Tx to complete the canCommit phase.
+
+            final CountDownLatch latch = new CountDownLatch(1);
+            canCommitFuture.onComplete(new OnComplete<Object>() {
+                @Override
+                public void onComplete(final Throwable t, final Object resp) {
+                    latch.countDown();
+                }
+            }, getSystem().dispatcher());
+
+            assertEquals("2nd CanCommit complete", true, latch.await(5, TimeUnit.SECONDS));
+
+            final InOrder inOrder = inOrder(cohort1, cohort2);
+            inOrder.verify(cohort1).canCommit();
+            inOrder.verify(cohort1).preCommit();
+            inOrder.verify(cohort1).commit();
+            inOrder.verify(cohort2).canCommit();
+        }};
+    }
+
+    @Test
+    public void testPreCommitPhaseFailure() throws Throwable {
+        testPreCommitPhaseFailure(true);
+        testPreCommitPhaseFailure(false);
+    }
+
+    private void testPreCommitPhaseFailure(final boolean readWrite) throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testPreCommitPhaseFailure-" + readWrite);
+
+            waitUntilLeader(shard);
+
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification1 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort1 = mock(ShardDataTreeCohort.class, "cohort1");
+            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort1).canCommit();
+            doReturn(Futures.immediateFailedFuture(new IllegalStateException("mock"))).when(cohort1).preCommit();
+
+            final String transactionID2 = "tx2";
+            final MutableCompositeModification modification2 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort2 = mock(ShardDataTreeCohort.class, "cohort2");
+            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort2).canCommit();
+
+            final FiniteDuration duration = duration("5 seconds");
+            final Timeout timeout = new Timeout(duration);
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort1, transactionID1, modification1), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort2, transactionID2, modification2), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // Send the CanCommitTransaction message for the first Tx.
+
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                expectMsgClass(duration, CanCommitTransactionReply.class));
+            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+            // Send the CanCommitTransaction message for the 2nd Tx. This should get queued and
+            // processed after the first Tx completes.
+
+            final Future<Object> canCommitFuture = Patterns.ask(shard,
+                    new CanCommitTransaction(transactionID2, CURRENT_VERSION).toSerializable(), timeout);
+
+            // Send the CommitTransaction message for the first Tx. This should send back an error
+            // and trigger the 2nd Tx to proceed.
+
+            shard.tell(new CommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, akka.actor.Status.Failure.class);
+
+            // Wait for the 2nd Tx to complete the canCommit phase.
+
+            final CountDownLatch latch = new CountDownLatch(1);
+            canCommitFuture.onComplete(new OnComplete<Object>() {
+                @Override
+                public void onComplete(final Throwable t, final Object resp) {
+                    latch.countDown();
+                }
+            }, getSystem().dispatcher());
+
+            assertEquals("2nd CanCommit complete", true, latch.await(5, TimeUnit.SECONDS));
+
+            final InOrder inOrder = inOrder(cohort1, cohort2);
+            inOrder.verify(cohort1).canCommit();
+            inOrder.verify(cohort1).preCommit();
+            inOrder.verify(cohort2).canCommit();
+        }};
+    }
+
+    @Test
+    public void testCanCommitPhaseFailure() throws Throwable {
+        testCanCommitPhaseFailure(true);
+        testCanCommitPhaseFailure(false);
+    }
+
+    private void testCanCommitPhaseFailure(final boolean readWrite) throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testCanCommitPhaseFailure-" + readWrite);
+
+            waitUntilLeader(shard);
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort = mock(ShardDataTreeCohort.class, "cohort1");
             doReturn(Futures.immediateFailedFuture(new IllegalStateException("mock"))).when(cohort).canCommit();
 
-            // Simulate the ForwardedReadyTransaction messages that would be sent
-            // by the ShardTransaction.
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID1, modification), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // Send the CanCommitTransaction message.
+
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, akka.actor.Status.Failure.class);
+
+            // Send another can commit to ensure the failed one got cleaned up.
+
+            reset(cohort);
+
+            final String transactionID2 = "tx2";
+            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).canCommit();
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID2, modification), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            shard.tell(new CanCommitTransaction(transactionID2, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply reply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(CanCommitTransactionReply.class));
+            assertEquals("getCanCommit", true, reply.getCanCommit());
+        }};
+    }
+
+    @Test
+    public void testCanCommitPhaseFalseResponse() throws Throwable {
+        testCanCommitPhaseFalseResponse(true);
+        testCanCommitPhaseFalseResponse(false);
+    }
+
+    private void testCanCommitPhaseFalseResponse(final boolean readWrite) throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testCanCommitPhaseFalseResponse-" + readWrite);
+
+            waitUntilLeader(shard);
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort = mock(ShardDataTreeCohort.class, "cohort1");
+            doReturn(Futures.immediateFuture(Boolean.FALSE)).when(cohort).canCommit();
 
-            shard.tell(new ForwardedReadyTransaction(transactionID, CURRENT_VERSION,
-                    cohort, modification, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID1, modification), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             // Send the CanCommitTransaction message.
 
-            shard.tell(new CanCommitTransaction(transactionID).toSerializable(), getRef());
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            CanCommitTransactionReply reply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(CanCommitTransactionReply.class));
+            assertEquals("getCanCommit", false, reply.getCanCommit());
+
+            // Send another can commit to ensure the failed one got cleaned up.
+
+            reset(cohort);
+
+            final String transactionID2 = "tx2";
+            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).canCommit();
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID2, modification), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            shard.tell(new CanCommitTransaction(transactionID2, CURRENT_VERSION).toSerializable(), getRef());
+            reply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(CanCommitTransactionReply.class));
+            assertEquals("getCanCommit", true, reply.getCanCommit());
+        }};
+    }
+
+    @Test
+    public void testImmediateCommitWithCanCommitPhaseFailure() throws Throwable {
+        testImmediateCommitWithCanCommitPhaseFailure(true);
+        testImmediateCommitWithCanCommitPhaseFailure(false);
+    }
+
+    private void testImmediateCommitWithCanCommitPhaseFailure(final boolean readWrite) throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testImmediateCommitWithCanCommitPhaseFailure-" + readWrite);
+
+            waitUntilLeader(shard);
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort = mock(ShardDataTreeCohort.class, "cohort1");
+            doReturn(Futures.immediateFailedFuture(new IllegalStateException("mock"))).when(cohort).canCommit();
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID1, modification, true), getRef());
+
+            expectMsgClass(duration, akka.actor.Status.Failure.class);
+
+            // Send another can commit to ensure the failed one got cleaned up.
+
+            reset(cohort);
+
+            final String transactionID2 = "tx2";
+            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).canCommit();
+            doReturn(Futures.immediateFuture(null)).when(cohort).preCommit();
+            doReturn(Futures.immediateFuture(null)).when(cohort).commit();
+            final DataTreeCandidateTip candidate = mock(DataTreeCandidateTip.class);
+            final DataTreeCandidateNode candidateRoot = mock(DataTreeCandidateNode.class);
+            doReturn(ModificationType.UNMODIFIED).when(candidateRoot).getModificationType();
+            doReturn(candidateRoot).when(candidate).getRootNode();
+            doReturn(YangInstanceIdentifier.EMPTY).when(candidate).getRootPath();
+            doReturn(candidate).when(cohort).getCandidate();
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID2, modification, true), getRef());
+
+            expectMsgClass(duration, CommitTransactionReply.class);
+        }};
+    }
+
+    @Test
+    public void testImmediateCommitWithCanCommitPhaseFalseResponse() throws Throwable {
+        testImmediateCommitWithCanCommitPhaseFalseResponse(true);
+        testImmediateCommitWithCanCommitPhaseFalseResponse(false);
+    }
+
+    private void testImmediateCommitWithCanCommitPhaseFalseResponse(final boolean readWrite) throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testImmediateCommitWithCanCommitPhaseFalseResponse-" + readWrite);
+
+            waitUntilLeader(shard);
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            final String transactionID = "tx1";
+            final MutableCompositeModification modification = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort = mock(ShardDataTreeCohort.class, "cohort1");
+            doReturn(Futures.immediateFuture(Boolean.FALSE)).when(cohort).canCommit();
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID, modification, true), getRef());
+
             expectMsgClass(duration, akka.actor.Status.Failure.class);
 
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            // Send another can commit to ensure the failed one got cleaned up.
+
+            reset(cohort);
+
+            final String transactionID2 = "tx2";
+            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).canCommit();
+            doReturn(Futures.immediateFuture(null)).when(cohort).preCommit();
+            doReturn(Futures.immediateFuture(null)).when(cohort).commit();
+            final DataTreeCandidateTip candidate = mock(DataTreeCandidateTip.class);
+            final DataTreeCandidateNode candidateRoot = mock(DataTreeCandidateNode.class);
+            doReturn(ModificationType.UNMODIFIED).when(candidateRoot).getModificationType();
+            doReturn(candidateRoot).when(candidate).getRootNode();
+            doReturn(YangInstanceIdentifier.EMPTY).when(candidate).getRootPath();
+            doReturn(candidate).when(cohort).getCandidate();
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID2, modification, true), getRef());
+
+            expectMsgClass(duration, CommitTransactionReply.class);
         }};
     }
 
     @Test
     public void testAbortBeforeFinishCommit() throws Throwable {
+        testAbortBeforeFinishCommit(true);
+        testAbortBeforeFinishCommit(false);
+    }
+
+    private void testAbortBeforeFinishCommit(final boolean readWrite) throws Throwable {
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testAbortBeforeFinishCommit");
+                    "testAbortBeforeFinishCommit-" + readWrite);
 
             waitUntilLeader(shard);
 
             final FiniteDuration duration = duration("5 seconds");
-            InMemoryDOMDataStore dataStore = shard.underlyingActor().getDataStore();
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
 
             final String transactionID = "tx1";
-            Function<DOMStoreThreePhaseCommitCohort,ListenableFuture<Void>> preCommit =
-                          new Function<DOMStoreThreePhaseCommitCohort,ListenableFuture<Void>>() {
-                @Override
-                public ListenableFuture<Void> apply(final DOMStoreThreePhaseCommitCohort cohort) {
-                    ListenableFuture<Void> preCommitFuture = cohort.preCommit();
-
-                    // Simulate an AbortTransaction message occurring during replication, after
-                    // persisting and before finishing the commit to the in-memory store.
-                    // We have no followers so due to optimizations in the RaftActor, it does not
-                    // attempt replication and thus we can't send an AbortTransaction message b/c
-                    // it would be processed too late after CommitTransaction completes. So we'll
-                    // simulate an AbortTransaction message occurring during replication by calling
-                    // the shard directly.
-                    //
-                    shard.underlyingActor().doAbortTransaction(transactionID, null);
-
-                    return preCommitFuture;
-                }
+            final Function<ShardDataTreeCohort, ListenableFuture<Void>> preCommit =
+                          cohort -> {
+                final ListenableFuture<Void> preCommitFuture = cohort.preCommit();
+
+                // Simulate an AbortTransaction message occurring during replication, after
+                // persisting and before finishing the commit to the in-memory store.
+                // We have no followers so due to optimizations in the RaftActor, it does not
+                // attempt replication and thus we can't send an AbortTransaction message b/c
+                // it would be processed too late after CommitTransaction completes. So we'll
+                // simulate an AbortTransaction message occurring during replication by calling
+                // the shard directly.
+                //
+                shard.underlyingActor().doAbortTransaction(transactionID, null);
+
+                return preCommitFuture;
             };
 
-            MutableCompositeModification modification = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort = setupMockWriteTransaction("cohort1", dataStore,
+            final MutableCompositeModification modification = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort = setupMockWriteTransaction("cohort1", dataStore,
                     TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME),
                     modification, preCommit);
 
-            shard.tell(new ForwardedReadyTransaction(transactionID, CURRENT_VERSION,
-                    cohort, modification, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID, modification), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
-            shard.tell(new CanCommitTransaction(transactionID).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
-                    expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            shard.tell(new CanCommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                expectMsgClass(duration, CanCommitTransactionReply.class));
             assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
-            shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
-            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(new CommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.class);
 
-            NormalizedNode<?, ?> node = readStore(shard, TestModel.TEST_PATH);
+            final NormalizedNode<?, ?> node = readStore(shard, TestModel.TEST_PATH);
 
             // Since we're simulating an abort occurring during replication and before finish commit,
             // the data should still get written to the in-memory store since we've gotten past
             // canCommit and preCommit and persisted the data.
             assertNotNull(TestModel.TEST_QNAME.getLocalName() + " not found", node);
-
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
     }
 
     @Test
     public void testTransactionCommitTimeout() throws Throwable {
+        testTransactionCommitTimeout(true);
+        testTransactionCommitTimeout(false);
+    }
+
+    private void testTransactionCommitTimeout(final boolean readWrite) throws Throwable {
         dataStoreContextBuilder.shardTransactionCommitTimeoutInSeconds(1);
 
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testTransactionCommitTimeout");
+                    "testTransactionCommitTimeout-" + readWrite);
 
             waitUntilLeader(shard);
 
             final FiniteDuration duration = duration("5 seconds");
 
-            InMemoryDOMDataStore dataStore = shard.underlyingActor().getDataStore();
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
 
             writeToStore(shard, TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
             writeToStore(shard, TestModel.OUTER_LIST_PATH,
@@ -1184,9 +1675,9 @@ public class ShardTest extends AbstractActorTest {
 
             // Create 1st Tx - will timeout
 
-            String transactionID1 = "tx1";
-            MutableCompositeModification modification1 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort1 = setupMockWriteTransaction("cohort1", dataStore,
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification1 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort1 = setupMockWriteTransaction("cohort1", dataStore,
                     YangInstanceIdentifier.builder(TestModel.OUTER_LIST_PATH)
                         .nodeWithKey(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 1).build(),
                     ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 1),
@@ -1194,53 +1685,54 @@ public class ShardTest extends AbstractActorTest {
 
             // Create 2nd Tx
 
-            String transactionID2 = "tx3";
-            MutableCompositeModification modification2 = new MutableCompositeModification();
-            YangInstanceIdentifier listNodePath = YangInstanceIdentifier.builder(TestModel.OUTER_LIST_PATH)
+            final String transactionID2 = "tx3";
+            final MutableCompositeModification modification2 = new MutableCompositeModification();
+            final YangInstanceIdentifier listNodePath = YangInstanceIdentifier.builder(TestModel.OUTER_LIST_PATH)
                 .nodeWithKey(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 2).build();
-            DOMStoreThreePhaseCommitCohort cohort2 = setupMockWriteTransaction("cohort3", dataStore,
+            final ShardDataTreeCohort cohort2 = setupMockWriteTransaction("cohort3", dataStore,
                     listNodePath,
                     ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, 2),
                     modification2);
 
             // Ready the Tx's
 
-            shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
-                    cohort1, modification1, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort1, transactionID1, modification1), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
-            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort2, transactionID2, modification2), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             // canCommit 1st Tx. We don't send the commit so it should timeout.
 
-            shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
-            expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CanCommitTransactionReply.class);
 
             // canCommit the 2nd Tx - it should complete after the 1st Tx times out.
 
-            shard.tell(new CanCommitTransaction(transactionID2).toSerializable(), getRef());
-            expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(new CanCommitTransaction(transactionID2, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CanCommitTransactionReply.class);
+
+            // Try to commit the 1st Tx - should fail as it's not the current Tx.
+
+            shard.tell(new CommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, akka.actor.Status.Failure.class);
 
             // Commit the 2nd Tx.
 
-            shard.tell(new CommitTransaction(transactionID2).toSerializable(), getRef());
-            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(new CommitTransaction(transactionID2, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.class);
 
-            NormalizedNode<?, ?> node = readStore(shard, listNodePath);
+            final NormalizedNode<?, ?> node = readStore(shard, listNodePath);
             assertNotNull(listNodePath + " not found", node);
-
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
     }
 
     @Test
     public void testTransactionCommitQueueCapacityExceeded() throws Throwable {
-        dataStoreContextBuilder.shardTransactionCommitQueueCapacity(1);
+        dataStoreContextBuilder.shardTransactionCommitQueueCapacity(2);
 
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
                     "testTransactionCommitQueueCapacityExceeded");
 
@@ -1248,135 +1740,307 @@ public class ShardTest extends AbstractActorTest {
 
             final FiniteDuration duration = duration("5 seconds");
 
-            InMemoryDOMDataStore dataStore = shard.underlyingActor().getDataStore();
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
 
-            String transactionID1 = "tx1";
-            MutableCompositeModification modification1 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort1 = setupMockWriteTransaction("cohort1", dataStore,
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification1 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort1 = setupMockWriteTransaction("cohort1", dataStore,
                     TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME), modification1);
 
-            String transactionID2 = "tx2";
-            MutableCompositeModification modification2 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort2 = setupMockWriteTransaction("cohort2", dataStore,
+            final String transactionID2 = "tx2";
+            final MutableCompositeModification modification2 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort2 = setupMockWriteTransaction("cohort2", dataStore,
                     TestModel.OUTER_LIST_PATH,
                     ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build(),
                     modification2);
 
-            String transactionID3 = "tx3";
-            MutableCompositeModification modification3 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort3 = setupMockWriteTransaction("cohort3", dataStore,
+            final String transactionID3 = "tx3";
+            final MutableCompositeModification modification3 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort3 = setupMockWriteTransaction("cohort3", dataStore,
                     TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME), modification3);
 
             // Ready the Tx's
 
-            shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
-                    cohort1, modification1, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort1, transactionID1, modification1), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort2, transactionID2, modification2), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
-            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            // The 3rd Tx should exceed queue capacity and fail.
 
-            shard.tell(new ForwardedReadyTransaction(transactionID3, CURRENT_VERSION,
-                    cohort3, modification3, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort3, transactionID3, modification3), getRef());
+            expectMsgClass(duration, akka.actor.Status.Failure.class);
 
             // canCommit 1st Tx.
 
-            shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
-            expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CanCommitTransactionReply.class);
 
             // canCommit the 2nd Tx - it should get queued.
 
-            shard.tell(new CanCommitTransaction(transactionID2).toSerializable(), getRef());
+            shard.tell(new CanCommitTransaction(transactionID2, CURRENT_VERSION).toSerializable(), getRef());
 
             // canCommit the 3rd Tx - should exceed queue capacity and fail.
 
-            shard.tell(new CanCommitTransaction(transactionID3).toSerializable(), getRef());
+            shard.tell(new CanCommitTransaction(transactionID3, CURRENT_VERSION).toSerializable(), getRef());
             expectMsgClass(duration, akka.actor.Status.Failure.class);
+        }};
+    }
+
+    @Test
+    public void testTransactionCommitWithPriorExpiredCohortEntries() throws Throwable {
+        dataStoreContextBuilder.shardCommitQueueExpiryTimeoutInMillis(1300).shardTransactionCommitTimeoutInSeconds(1);
+
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testTransactionCommitWithPriorExpiredCohortEntries");
+
+            waitUntilLeader(shard);
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
+
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification1 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort1 = setupMockWriteTransaction("cohort1", dataStore,
+                    TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME), modification1);
+
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort1, transactionID1, modification1), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            final String transactionID2 = "tx2";
+            final MutableCompositeModification modification2 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort2 = setupMockWriteTransaction("cohort2", dataStore,
+                    TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME), modification2);
+
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort2, transactionID2, modification2), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            final String transactionID3 = "tx3";
+            final MutableCompositeModification modification3 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort3 = setupMockWriteTransaction("cohort3", dataStore,
+                    TestModel.TEST2_PATH, ImmutableNodes.containerNode(TestModel.TEST2_QNAME), modification3);
+
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort3, transactionID3, modification3), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // All Tx's are readied. We'll send canCommit for the last one but not the others. The others
+            // should expire from the queue and the last one should be processed.
+
+            shard.tell(new CanCommitTransaction(transactionID3, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CanCommitTransactionReply.class);
+        }};
+    }
+
+    @Test
+    public void testTransactionCommitWithSubsequentExpiredCohortEntry() throws Throwable {
+        dataStoreContextBuilder.shardCommitQueueExpiryTimeoutInMillis(1300).shardTransactionCommitTimeoutInSeconds(1);
 
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testTransactionCommitWithSubsequentExpiredCohortEntry");
+
+            waitUntilLeader(shard);
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
+
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification1 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort1 = setupMockWriteTransaction("cohort1", dataStore,
+                    TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME), modification1);
+
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort1, transactionID1, modification1), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // CanCommit the first one so it's the current in-progress CohortEntry.
+
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CanCommitTransactionReply.class);
+
+            // Ready the second Tx.
+
+            final String transactionID2 = "tx2";
+            final MutableCompositeModification modification2 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort2 = setupMockWriteTransaction("cohort2", dataStore,
+                    TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME), modification2);
+
+            shard.tell(prepareReadyTransactionMessage(false, shard.underlyingActor(), cohort2, transactionID2, modification2), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // Ready the third Tx.
+
+            final String transactionID3 = "tx3";
+            final DataTreeModification modification3 = dataStore.newModification();
+            new WriteModification(TestModel.TEST2_PATH, ImmutableNodes.containerNode(TestModel.TEST2_QNAME))
+                    .apply(modification3);
+                modification3.ready();
+            final ReadyLocalTransaction readyMessage = new ReadyLocalTransaction(transactionID3, modification3, true);
+
+            shard.tell(readyMessage, getRef());
+
+            // Commit the first Tx. After completing, the second should expire from the queue and the third
+            // Tx committed.
+
+            shard.tell(new CommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.class);
+
+            // Expect commit reply from the third Tx.
+
+            expectMsgClass(duration, CommitTransactionReply.class);
+
+            final NormalizedNode<?, ?> node = readStore(shard, TestModel.TEST2_PATH);
+            assertNotNull(TestModel.TEST2_PATH + " not found", node);
         }};
     }
 
     @Test
     public void testCanCommitBeforeReadyFailure() throws Throwable {
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
                     "testCanCommitBeforeReadyFailure");
 
-            shard.tell(new CanCommitTransaction("tx").toSerializable(), getRef());
+            shard.tell(new CanCommitTransaction("tx", CURRENT_VERSION).toSerializable(), getRef());
             expectMsgClass(duration("5 seconds"), akka.actor.Status.Failure.class);
-
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
     }
 
     @Test
-    public void testAbortTransaction() throws Throwable {
+    public void testAbortCurrentTransaction() throws Throwable {
+        testAbortCurrentTransaction(true);
+        testAbortCurrentTransaction(false);
+    }
+
+    private void testAbortCurrentTransaction(final boolean readWrite) throws Throwable {
         new ShardTestKit(getSystem()) {{
-            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testAbortTransaction");
+                    "testAbortCurrentTransaction-" + readWrite);
 
             waitUntilLeader(shard);
 
             // Setup 2 simulated transactions with mock cohorts. The first one will be aborted.
 
-            String transactionID1 = "tx1";
-            MutableCompositeModification modification1 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort1 = mock(DOMStoreThreePhaseCommitCohort.class, "cohort1");
+            final String transactionID1 = "tx1";
+            final MutableCompositeModification modification1 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort1 = mock(ShardDataTreeCohort.class, "cohort1");
             doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort1).canCommit();
             doReturn(Futures.immediateFuture(null)).when(cohort1).abort();
 
-            String transactionID2 = "tx2";
-            MutableCompositeModification modification2 = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort2 = mock(DOMStoreThreePhaseCommitCohort.class, "cohort2");
+            final String transactionID2 = "tx2";
+            final MutableCompositeModification modification2 = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort2 = mock(ShardDataTreeCohort.class, "cohort2");
             doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort2).canCommit();
 
-            FiniteDuration duration = duration("5 seconds");
+            final FiniteDuration duration = duration("5 seconds");
             final Timeout timeout = new Timeout(duration);
 
-            // Simulate the ForwardedReadyTransaction messages that would be sent
-            // by the ShardTransaction.
-
-            shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
-                    cohort1, modification1, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort1, transactionID1, modification1), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
-            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort2, transactionID2, modification2), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             // Send the CanCommitTransaction message for the first Tx.
 
-            shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
-                    expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            shard.tell(new CanCommitTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(duration, CanCommitTransactionReply.class));
             assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
             // Send the CanCommitTransaction message for the 2nd Tx. This should get queued and
             // processed after the first Tx completes.
 
-            Future<Object> canCommitFuture = Patterns.ask(shard,
-                    new CanCommitTransaction(transactionID2).toSerializable(), timeout);
+            final Future<Object> canCommitFuture = Patterns.ask(shard,
+                    new CanCommitTransaction(transactionID2, CURRENT_VERSION).toSerializable(), timeout);
 
             // Send the AbortTransaction message for the first Tx. This should trigger the 2nd
             // Tx to proceed.
 
-            shard.tell(new AbortTransaction(transactionID1).toSerializable(), getRef());
-            expectMsgClass(duration, AbortTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(new AbortTransaction(transactionID1, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, AbortTransactionReply.class);
 
             // Wait for the 2nd Tx to complete the canCommit phase.
 
             Await.ready(canCommitFuture, duration);
 
-            InOrder inOrder = inOrder(cohort1, cohort2);
+            final InOrder inOrder = inOrder(cohort1, cohort2);
             inOrder.verify(cohort1).canCommit();
             inOrder.verify(cohort2).canCommit();
+        }};
+    }
+
+    @Test
+    public void testAbortQueuedTransaction() throws Throwable {
+        testAbortQueuedTransaction(true);
+        testAbortQueuedTransaction(false);
+    }
+
+    private void testAbortQueuedTransaction(final boolean readWrite) throws Throwable {
+        dataStoreContextBuilder.shardTransactionCommitTimeoutInSeconds(1);
+        new ShardTestKit(getSystem()) {{
+            final AtomicReference<CountDownLatch> cleaupCheckLatch = new AtomicReference<>();
+            @SuppressWarnings("serial")
+            final Creator<Shard> creator = () -> new Shard(newShardBuilder()) {
+                @Override
+                public void handleCommand(final Object message) {
+                    super.handleCommand(message);
+                    if(TX_COMMIT_TIMEOUT_CHECK_MESSAGE.equals(message)) {
+                        if(cleaupCheckLatch.get() != null) {
+                            cleaupCheckLatch.get().countDown();
+                        }
+                    }
+                }
+            };
+
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    Props.create(new DelegatingShardCreator(creator)).withDispatcher(
+                            Dispatchers.DefaultDispatcherId()), "testAbortQueuedTransaction-" + readWrite);
+
+            waitUntilLeader(shard);
+
+            final String transactionID = "tx1";
+
+            final MutableCompositeModification modification = new MutableCompositeModification();
+            final ShardDataTreeCohort cohort = mock(ShardDataTreeCohort.class, "cohort");
+            doReturn(Futures.immediateFuture(null)).when(cohort).abort();
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            // Ready the tx.
+
+            shard.tell(prepareReadyTransactionMessage(readWrite, shard.underlyingActor(), cohort, transactionID, modification), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            assertEquals("getPendingTxCommitQueueSize", 1, shard.underlyingActor().getPendingTxCommitQueueSize());
+
+            // Send the AbortTransaction message.
+
+            shard.tell(new AbortTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+            expectMsgClass(duration, AbortTransactionReply.class);
+
+            verify(cohort).abort();
+
+            // Verify the tx cohort is removed from queue at the cleanup check interval.
 
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            cleaupCheckLatch.set(new CountDownLatch(1));
+            assertEquals("TX_COMMIT_TIMEOUT_CHECK_MESSAGE received", true,
+                    cleaupCheckLatch.get().await(5, TimeUnit.SECONDS));
+
+            assertEquals("getPendingTxCommitQueueSize", 0, shard.underlyingActor().getPendingTxCommitQueueSize());
+
+            // Now send CanCommitTransaction - should fail.
+
+            shard.tell(new CanCommitTransaction(transactionID, CURRENT_VERSION).toSerializable(), getRef());
+
+            Throwable failure = expectMsgClass(duration, akka.actor.Status.Failure.class).cause();
+            assertTrue("Failure type", failure instanceof IllegalStateException);
         }};
     }
 
@@ -1391,85 +2055,69 @@ public class ShardTest extends AbstractActorTest {
     }
 
     @SuppressWarnings("serial")
-    public void testCreateSnapshot(final boolean persistent, final String shardActorName) throws Exception{
-
-        final AtomicReference<Object> savedSnapshot = new AtomicReference<>();
-        class DelegatingPersistentDataProvider implements DataPersistenceProvider {
-            DataPersistenceProvider delegate;
-
-            DelegatingPersistentDataProvider(DataPersistenceProvider delegate) {
-                this.delegate = delegate;
-            }
+    private void testCreateSnapshot(final boolean persistent, final String shardActorName) throws Exception{
 
-            @Override
-            public boolean isRecoveryApplicable() {
-                return delegate.isRecoveryApplicable();
-            }
+        final AtomicReference<CountDownLatch> latch = new AtomicReference<>(new CountDownLatch(1));
 
-            @Override
-            public <T> void persist(T o, Procedure<T> procedure) {
-                delegate.persist(o, procedure);
+        final AtomicReference<Object> savedSnapshot = new AtomicReference<>();
+        class TestPersistentDataProvider extends DelegatingPersistentDataProvider {
+            TestPersistentDataProvider(final DataPersistenceProvider delegate) {
+                super(delegate);
             }
 
             @Override
-            public void saveSnapshot(Object o) {
+            public void saveSnapshot(final Object o) {
                 savedSnapshot.set(o);
-                delegate.saveSnapshot(o);
-            }
-
-            @Override
-            public void deleteSnapshots(SnapshotSelectionCriteria criteria) {
-                delegate.deleteSnapshots(criteria);
-            }
-
-            @Override
-            public void deleteMessages(long sequenceNumber) {
-                delegate.deleteMessages(sequenceNumber);
+                super.saveSnapshot(o);
             }
         }
 
         dataStoreContextBuilder.persistent(persistent);
 
         new ShardTestKit(getSystem()) {{
-            final AtomicReference<CountDownLatch> latch = new AtomicReference<>(new CountDownLatch(1));
-            Creator<Shard> creator = new Creator<Shard>() {
-                @Override
-                public Shard create() throws Exception {
-                    return new Shard(shardID, Collections.<ShardIdentifier,String>emptyMap(),
-                            newDatastoreContext(), SCHEMA_CONTEXT) {
+            class TestShard extends Shard {
 
-                        DelegatingPersistentDataProvider delegating;
+                protected TestShard(AbstractBuilder<?, ?> builder) {
+                    super(builder);
+                    setPersistence(new TestPersistentDataProvider(super.persistence()));
+                }
 
-                        @Override
-                        protected DataPersistenceProvider persistence() {
-                            if(delegating == null) {
-                                delegating = new DelegatingPersistentDataProvider(super.persistence());
-                            }
+                @Override
+                public void handleCommand(final Object message) {
+                    super.handleCommand(message);
 
-                            return delegating;
-                        }
+                    // XXX:  commit_snapshot equality check references RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT
+                    if (message instanceof SaveSnapshotSuccess || "commit_snapshot".equals(message.toString())) {
+                        latch.get().countDown();
+                    }
+                }
 
-                        @Override
-                        protected void commitSnapshot(final long sequenceNumber) {
-                            super.commitSnapshot(sequenceNumber);
-                            latch.get().countDown();
-                        }
-                    };
+                @Override
+                public RaftActorContext getRaftActorContext() {
+                    return super.getRaftActorContext();
                 }
-            };
+            }
 
-            TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final Creator<Shard> creator = () -> new TestShard(newShardBuilder());
+
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
                     Props.create(new DelegatingShardCreator(creator)), shardActorName);
 
             waitUntilLeader(shard);
-
             writeToStore(shard, TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
 
-            NormalizedNode<?,?> expectedRoot = readStore(shard, YangInstanceIdentifier.builder().build());
+            final NormalizedNode<?,?> expectedRoot = readStore(shard, YangInstanceIdentifier.EMPTY);
 
-            CaptureSnapshot capture = new CaptureSnapshot(-1, -1, -1, -1);
-            shard.tell(capture, getRef());
+            // Trigger creation of a snapshot by ensuring
+            final RaftActorContext raftActorContext = ((TestShard) shard.underlyingActor()).getRaftActorContext();
+            raftActorContext.getSnapshotManager().capture(mock(ReplicatedLogEntry.class), -1);
+            awaitAndValidateSnapshot(expectedRoot);
 
+            raftActorContext.getSnapshotManager().capture(mock(ReplicatedLogEntry.class), -1);
+            awaitAndValidateSnapshot(expectedRoot);
+        }
+
+        private void awaitAndValidateSnapshot(NormalizedNode<?,?> expectedRoot) throws InterruptedException {
             assertEquals("Snapshot saved", true, latch.get().await(5, TimeUnit.SECONDS));
 
             assertTrue("Invalid saved snapshot " + savedSnapshot.get(),
@@ -1479,22 +2127,11 @@ public class ShardTest extends AbstractActorTest {
 
             latch.set(new CountDownLatch(1));
             savedSnapshot.set(null);
-
-            shard.tell(capture, getRef());
-
-            assertEquals("Snapshot saved", true, latch.get().await(5, TimeUnit.SECONDS));
-
-            assertTrue("Invalid saved snapshot " + savedSnapshot.get(),
-                    savedSnapshot.get() instanceof Snapshot);
-
-            verifySnapshot((Snapshot)savedSnapshot.get(), expectedRoot);
-
-            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }
 
-        private void verifySnapshot(Snapshot snapshot, NormalizedNode<?,?> expectedRoot) {
+        private void verifySnapshot(final Snapshot snapshot, final NormalizedNode<?,?> expectedRoot) {
 
-            NormalizedNode<?, ?> actual = SerializationUtils.deserializeNormalizedNode(snapshot.getState());
+            final NormalizedNode<?, ?> actual = SerializationUtils.deserializeNormalizedNode(snapshot.getState());
             assertEquals("Root node", expectedRoot, actual);
 
         }};
@@ -1503,29 +2140,29 @@ public class ShardTest extends AbstractActorTest {
     /**
      * This test simply verifies that the applySnapShot logic will work
      * @throws ReadFailedException
+     * @throws DataValidationFailedException
      */
     @Test
-    public void testInMemoryDataStoreRestore() throws ReadFailedException {
-        InMemoryDOMDataStore store = new InMemoryDOMDataStore("test", MoreExecutors.sameThreadExecutor());
-
-        store.onGlobalContextUpdated(SCHEMA_CONTEXT);
+    public void testInMemoryDataTreeRestore() throws ReadFailedException, DataValidationFailedException {
+        final DataTree store = InMemoryDataTreeFactory.getInstance().create(TreeType.OPERATIONAL);
+        store.setSchemaContext(SCHEMA_CONTEXT);
 
-        DOMStoreWriteTransaction putTransaction = store.newWriteOnlyTransaction();
+        final DataTreeModification putTransaction = store.takeSnapshot().newModification();
         putTransaction.write(TestModel.TEST_PATH,
             ImmutableNodes.containerNode(TestModel.TEST_QNAME));
-        commitTransaction(putTransaction);
+        commitTransaction(store, putTransaction);
 
 
-        NormalizedNode<?, ?> expected = readStore(store);
+        final NormalizedNode<?, ?> expected = readStore(store, YangInstanceIdentifier.EMPTY);
 
-        DOMStoreWriteTransaction writeTransaction = store.newWriteOnlyTransaction();
+        final DataTreeModification writeTransaction = store.takeSnapshot().newModification();
 
-        writeTransaction.delete(YangInstanceIdentifier.builder().build());
-        writeTransaction.write(YangInstanceIdentifier.builder().build(), expected);
+        writeTransaction.delete(YangInstanceIdentifier.EMPTY);
+        writeTransaction.write(YangInstanceIdentifier.EMPTY, expected);
 
-        commitTransaction(writeTransaction);
+        commitTransaction(store, writeTransaction);
 
-        NormalizedNode<?, ?> actual = readStore(store);
+        final NormalizedNode<?, ?> actual = readStore(store, YangInstanceIdentifier.EMPTY);
 
         assertEquals(expected, actual);
     }
@@ -1536,118 +2173,265 @@ public class ShardTest extends AbstractActorTest {
         final DatastoreContext persistentContext = DatastoreContext.newBuilder().
                 shardJournalRecoveryLogBatchSize(3).shardSnapshotBatchCount(5000).persistent(true).build();
 
-        final Props persistentProps = Shard.props(shardID, Collections.<ShardIdentifier, String>emptyMap(),
-                persistentContext, SCHEMA_CONTEXT);
+        final Props persistentProps = Shard.builder().id(shardID).datastoreContext(persistentContext).
+                schemaContext(SCHEMA_CONTEXT).props();
 
         final DatastoreContext nonPersistentContext = DatastoreContext.newBuilder().
                 shardJournalRecoveryLogBatchSize(3).shardSnapshotBatchCount(5000).persistent(false).build();
 
-        final Props nonPersistentProps = Shard.props(shardID, Collections.<ShardIdentifier, String>emptyMap(),
-                nonPersistentContext, SCHEMA_CONTEXT);
+        final Props nonPersistentProps = Shard.builder().id(shardID).datastoreContext(nonPersistentContext).
+                schemaContext(SCHEMA_CONTEXT).props();
 
         new ShardTestKit(getSystem()) {{
-            TestActorRef<Shard> shard1 = TestActorRef.create(getSystem(),
-                    persistentProps, "testPersistence1");
+            final TestActorRef<Shard> shard1 = actorFactory.createTestActor(persistentProps, "testPersistence1");
 
-            assertTrue("Recovery Applicable", shard1.underlyingActor().getDataPersistenceProvider().isRecoveryApplicable());
+            assertTrue("Recovery Applicable", shard1.underlyingActor().persistence().isRecoveryApplicable());
 
-            shard1.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            final TestActorRef<Shard> shard2 = actorFactory.createTestActor(nonPersistentProps, "testPersistence2");
 
-            TestActorRef<Shard> shard2 = TestActorRef.create(getSystem(),
-                    nonPersistentProps, "testPersistence2");
+            assertFalse("Recovery Not Applicable", shard2.underlyingActor().persistence().isRecoveryApplicable());
+        }};
+    }
+
+    @Test
+    public void testOnDatastoreContext() {
+        new ShardTestKit(getSystem()) {{
+            dataStoreContextBuilder.persistent(true);
 
-            assertFalse("Recovery Not Applicable", shard2.underlyingActor().getDataPersistenceProvider().isRecoveryApplicable());
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(newShardProps(), "testOnDatastoreContext");
 
-            shard2.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            assertEquals("isRecoveryApplicable", true,
+                    shard.underlyingActor().persistence().isRecoveryApplicable());
 
-        }};
+            waitUntilLeader(shard);
+
+            shard.tell(dataStoreContextBuilder.persistent(false).build(), ActorRef.noSender());
 
+            assertEquals("isRecoveryApplicable", false,
+                shard.underlyingActor().persistence().isRecoveryApplicable());
+
+            shard.tell(dataStoreContextBuilder.persistent(true).build(), ActorRef.noSender());
+
+            assertEquals("isRecoveryApplicable", true,
+                shard.underlyingActor().persistence().isRecoveryApplicable());
+        }};
     }
 
+    @Test
+    public void testRegisterRoleChangeListener() throws Exception {
+        new ShardTestKit(getSystem()) {
+            {
+                final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                        newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                        "testRegisterRoleChangeListener");
 
-    private NormalizedNode<?, ?> readStore(final InMemoryDOMDataStore store) throws ReadFailedException {
-        DOMStoreReadTransaction transaction = store.newReadOnlyTransaction();
-        CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> read =
-            transaction.read(YangInstanceIdentifier.builder().build());
+                waitUntilLeader(shard);
 
-        Optional<NormalizedNode<?, ?>> optional = read.checkedGet();
+                final TestActorRef<MessageCollectorActor> listener =
+                        TestActorRef.create(getSystem(), Props.create(MessageCollectorActor.class));
 
-        NormalizedNode<?, ?> normalizedNode = optional.get();
+                shard.tell(new RegisterRoleChangeListener(), listener);
 
-        transaction.close();
+                MessageCollectorActor.expectFirstMatching(listener, RegisterRoleChangeListenerReply.class);
 
-        return normalizedNode;
-    }
+                ShardLeaderStateChanged leaderStateChanged = MessageCollectorActor.expectFirstMatching(listener,
+                    ShardLeaderStateChanged.class);
+                assertEquals("getLocalShardDataTree present", true,
+                        leaderStateChanged.getLocalShardDataTree().isPresent());
+                assertSame("getLocalShardDataTree", shard.underlyingActor().getDataStore().getDataTree(),
+                    leaderStateChanged.getLocalShardDataTree().get());
 
-    private void commitTransaction(final DOMStoreWriteTransaction transaction) {
-        DOMStoreThreePhaseCommitCohort commitCohort = transaction.ready();
-        ListenableFuture<Void> future =
-            commitCohort.preCommit();
-        try {
-            future.get();
-            future = commitCohort.commit();
-            future.get();
-        } catch (InterruptedException | ExecutionException e) {
-        }
-    }
+                MessageCollectorActor.clearMessages(listener);
 
-    private AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>> noOpDataChangeListener() {
-        return new AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>() {
-            @Override
-            public void onDataChanged(
-                final AsyncDataChangeEvent<YangInstanceIdentifier, NormalizedNode<?, ?>> change) {
+                // Force a leader change
 
+                shard.tell(new RequestVote(10000, "member2", 50, 50), getRef());
+
+                leaderStateChanged = MessageCollectorActor.expectFirstMatching(listener,
+                        ShardLeaderStateChanged.class);
+                assertEquals("getLocalShardDataTree present", false,
+                        leaderStateChanged.getLocalShardDataTree().isPresent());
             }
         };
     }
 
-    static NormalizedNode<?,?> readStore(final TestActorRef<Shard> shard, final YangInstanceIdentifier id)
-            throws ExecutionException, InterruptedException {
-        return readStore(shard.underlyingActor().getDataStore(), id);
+    @Test
+    public void testFollowerInitialSyncStatus() throws Exception {
+        final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                "testFollowerInitialSyncStatus");
+
+        shard.underlyingActor().handleNonRaftCommand(new FollowerInitialSyncUpStatus(false, "member-1-shard-inventory-operational"));
+
+        assertEquals(false, shard.underlyingActor().getShardMBean().getFollowerInitialSyncStatus());
+
+        shard.underlyingActor().handleNonRaftCommand(new FollowerInitialSyncUpStatus(true, "member-1-shard-inventory-operational"));
+
+        assertEquals(true, shard.underlyingActor().getShardMBean().getFollowerInitialSyncStatus());
     }
 
-    public static NormalizedNode<?,?> readStore(final InMemoryDOMDataStore store, final YangInstanceIdentifier id)
-            throws ExecutionException, InterruptedException {
-        DOMStoreReadTransaction transaction = store.newReadOnlyTransaction();
+    @Test
+    public void testClusteredDataChangeListenerDelayedRegistration() throws Exception {
+        new ShardTestKit(getSystem()) {{
+            String testName = "testClusteredDataChangeListenerDelayedRegistration";
+            dataStoreContextBuilder.shardElectionTimeoutFactor(1000).
+                    customRaftPolicyImplementation(DisableElectionsRaftPolicy.class.getName());
+
+            final MockDataChangeListener listener = new MockDataChangeListener(1);
+            final ActorRef dclActor = actorFactory.createActor(DataChangeListener.props(listener),
+                    actorFactory.generateActorId(testName + "-DataChangeListener"));
+
+            setupInMemorySnapshotStore();
+
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardBuilder().props().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    actorFactory.generateActorId(testName + "-shard"));
+
+            waitUntilNoLeader(shard);
 
-        CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> future =
-            transaction.read(id);
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
 
-        Optional<NormalizedNode<?, ?>> optional = future.get();
-        NormalizedNode<?, ?> node = optional.isPresent()? optional.get() : null;
+            shard.tell(new RegisterChangeListener(path, dclActor, AsyncDataBroker.DataChangeScope.BASE, true), getRef());
+            final RegisterChangeListenerReply reply = expectMsgClass(duration("5 seconds"),
+                RegisterChangeListenerReply.class);
+            assertNotNull("getListenerRegistrationPath", reply.getListenerRegistrationPath());
+
+            shard.tell(DatastoreContext.newBuilderFrom(dataStoreContextBuilder.build()).
+                    customRaftPolicyImplementation(null).build(), ActorRef.noSender());
 
-        transaction.close();
+            listener.waitForChangeEvents();
+        }};
+    }
 
-        return node;
+    @Test
+    public void testClusteredDataChangeListenerRegistration() throws Exception {
+        new ShardTestKit(getSystem()) {{
+            String testName = "testClusteredDataChangeListenerRegistration";
+            final ShardIdentifier followerShardID = ShardIdentifier.create("inventory",
+                    MemberName.forName(actorFactory.generateActorId(testName + "-follower")), "config");
+
+            final ShardIdentifier leaderShardID = ShardIdentifier.create("inventory",
+                    MemberName.forName(actorFactory.generateActorId(testName + "-leader")), "config");
+
+            final TestActorRef<Shard> followerShard = actorFactory.createTestActor(
+                    Shard.builder().id(followerShardID).
+                        datastoreContext(dataStoreContextBuilder.shardElectionTimeoutFactor(1000).build()).
+                        peerAddresses(Collections.singletonMap(leaderShardID.toString(),
+                            "akka://test/user/" + leaderShardID.toString())).schemaContext(SCHEMA_CONTEXT).props().
+                    withDispatcher(Dispatchers.DefaultDispatcherId()), followerShardID.toString());
+
+            final TestActorRef<Shard> leaderShard = actorFactory.createTestActor(
+                    Shard.builder().id(leaderShardID).datastoreContext(newDatastoreContext()).
+                        peerAddresses(Collections.singletonMap(followerShardID.toString(),
+                            "akka://test/user/" + followerShardID.toString())).schemaContext(SCHEMA_CONTEXT).props().
+                    withDispatcher(Dispatchers.DefaultDispatcherId()), leaderShardID.toString());
+
+            leaderShard.tell(ElectionTimeout.INSTANCE, ActorRef.noSender());
+            String leaderPath = waitUntilLeader(followerShard);
+            assertEquals("Shard leader path", leaderShard.path().toString(), leaderPath);
+
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
+            final MockDataChangeListener listener = new MockDataChangeListener(1);
+            final ActorRef dclActor = actorFactory.createActor(DataChangeListener.props(listener),
+                    actorFactory.generateActorId(testName + "-DataChangeListener"));
+
+            followerShard.tell(new RegisterChangeListener(path, dclActor, AsyncDataBroker.DataChangeScope.BASE, true), getRef());
+            final RegisterChangeListenerReply reply = expectMsgClass(duration("5 seconds"),
+                RegisterChangeListenerReply.class);
+            assertNotNull("getListenerRegistratioznPath", reply.getListenerRegistrationPath());
+
+            writeToStore(followerShard, path, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
+
+            listener.waitForChangeEvents();
+        }};
     }
 
-    static void writeToStore(final TestActorRef<Shard> shard, final YangInstanceIdentifier id,
-            final NormalizedNode<?,?> node) throws ExecutionException, InterruptedException {
-        writeToStore(shard.underlyingActor().getDataStore(), id, node);
+    @Test
+    public void testClusteredDataTreeChangeListenerDelayedRegistration() throws Exception {
+        new ShardTestKit(getSystem()) {{
+            String testName = "testClusteredDataTreeChangeListenerDelayedRegistration";
+            dataStoreContextBuilder.shardElectionTimeoutFactor(1000).
+                    customRaftPolicyImplementation(DisableElectionsRaftPolicy.class.getName());
+
+            final MockDataTreeChangeListener listener = new MockDataTreeChangeListener(1);
+            final ActorRef dclActor = actorFactory.createActor(DataTreeChangeListenerActor.props(listener),
+                    actorFactory.generateActorId(testName + "-DataTreeChangeListener"));
+
+            setupInMemorySnapshotStore();
+
+            final TestActorRef<Shard> shard = actorFactory.createTestActor(
+                    newShardBuilder().props().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    actorFactory.generateActorId(testName + "-shard"));
+
+            waitUntilNoLeader(shard);
+
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
+
+            shard.tell(new RegisterDataTreeChangeListener(TestModel.TEST_PATH, dclActor, true), getRef());
+            final RegisterDataTreeChangeListenerReply reply = expectMsgClass(duration("5 seconds"),
+                    RegisterDataTreeChangeListenerReply.class);
+            assertNotNull("getListenerRegistrationPath", reply.getListenerRegistrationPath());
+
+            shard.tell(DatastoreContext.newBuilderFrom(dataStoreContextBuilder.build()).
+                    customRaftPolicyImplementation(null).build(), ActorRef.noSender());
+
+            listener.waitForChangeEvents();
+        }};
     }
 
-    public static void writeToStore(final InMemoryDOMDataStore store, final YangInstanceIdentifier id,
-            final NormalizedNode<?,?> node) throws ExecutionException, InterruptedException {
-        DOMStoreWriteTransaction transaction = store.newWriteOnlyTransaction();
+    @Test
+    public void testClusteredDataTreeChangeListenerRegistration() throws Exception {
+        new ShardTestKit(getSystem()) {{
+            String testName = "testClusteredDataTreeChangeListenerRegistration";
+            final ShardIdentifier followerShardID = ShardIdentifier.create("inventory",
+                    MemberName.forName(actorFactory.generateActorId(testName + "-follower")), "config");
+
+            final ShardIdentifier leaderShardID = ShardIdentifier.create("inventory",
+                    MemberName.forName(actorFactory.generateActorId(testName + "-leader")), "config");
+
+            final TestActorRef<Shard> followerShard = actorFactory.createTestActor(
+                    Shard.builder().id(followerShardID).
+                        datastoreContext(dataStoreContextBuilder.shardElectionTimeoutFactor(1000).build()).
+                        peerAddresses(Collections.singletonMap(leaderShardID.toString(),
+                            "akka://test/user/" + leaderShardID.toString())).schemaContext(SCHEMA_CONTEXT).props().
+                    withDispatcher(Dispatchers.DefaultDispatcherId()), followerShardID.toString());
+
+            final TestActorRef<Shard> leaderShard = actorFactory.createTestActor(
+                    Shard.builder().id(leaderShardID).datastoreContext(newDatastoreContext()).
+                        peerAddresses(Collections.singletonMap(followerShardID.toString(),
+                            "akka://test/user/" + followerShardID.toString())).schemaContext(SCHEMA_CONTEXT).props().
+                    withDispatcher(Dispatchers.DefaultDispatcherId()), leaderShardID.toString());
+
+            leaderShard.tell(ElectionTimeout.INSTANCE, ActorRef.noSender());
+            String leaderPath = waitUntilLeader(followerShard);
+            assertEquals("Shard leader path", leaderShard.path().toString(), leaderPath);
+
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
+            final MockDataTreeChangeListener listener = new MockDataTreeChangeListener(1);
+            final ActorRef dclActor = actorFactory.createActor(DataTreeChangeListenerActor.props(listener),
+                    actorFactory.generateActorId(testName + "-DataTreeChangeListener"));
+
+            followerShard.tell(new RegisterDataTreeChangeListener(TestModel.TEST_PATH, dclActor, true), getRef());
+            final RegisterDataTreeChangeListenerReply reply = expectMsgClass(duration("5 seconds"),
+                    RegisterDataTreeChangeListenerReply.class);
+            assertNotNull("getListenerRegistrationPath", reply.getListenerRegistrationPath());
 
-        transaction.write(id, node);
+            writeToStore(followerShard, path, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
 
-        DOMStoreThreePhaseCommitCohort commitCohort = transaction.ready();
-        commitCohort.preCommit().get();
-        commitCohort.commit().get();
+            listener.waitForChangeEvents();
+        }};
     }
 
-    @SuppressWarnings("serial")
-    private static final class DelegatingShardCreator implements Creator<Shard> {
-        private final Creator<Shard> delegate;
+    @Test
+    public void testServerRemoved() throws Exception {
+        final TestActorRef<MessageCollectorActor> parent = actorFactory.createTestActor(MessageCollectorActor.props());
 
-        DelegatingShardCreator(final Creator<Shard> delegate) {
-            this.delegate = delegate;
-        }
+        final ActorRef shard = parent.underlyingActor().context().actorOf(
+                newShardBuilder().props().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                "testServerRemoved");
 
-        @Override
-        public Shard create() throws Exception {
-            return delegate.create();
-        }
+        shard.tell(new ServerRemoved("test"), ActorRef.noSender());
+
+        MessageCollectorActor.expectFirstMatching(parent, ServerRemoved.class);
     }
 }