Bug 3195: Cleanup on error paths and error handling
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / test / java / org / opendaylight / controller / cluster / datastore / ShardTest.java
index 00e7a56c01106e1c2712a5a8d44cd29abc32e1ab..83b15b99df43f74e0a8a5d61d7493b1792c17e8b 100644 (file)
@@ -4,44 +4,49 @@ 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.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.inOrder;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.reset;
 import static org.opendaylight.controller.cluster.datastore.DataStoreVersions.CURRENT_VERSION;
 import akka.actor.ActorRef;
+import akka.actor.ActorSelection;
 import akka.actor.PoisonPill;
 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.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.List;
 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.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 import org.junit.Test;
 import org.mockito.InOrder;
 import org.opendaylight.controller.cluster.DataPersistenceProvider;
+import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
 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;
@@ -49,9 +54,15 @@ import org.opendaylight.controller.cluster.datastore.messages.CommitTransactionR
 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
 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;
@@ -59,69 +70,107 @@ 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.utils.InMemoryJournal;
-import org.opendaylight.controller.cluster.datastore.utils.InMemorySnapshotStore;
-import org.opendaylight.controller.cluster.datastore.utils.MessageCollectorActor;
 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.ApplyJournalEntries;
-import org.opendaylight.controller.cluster.raft.base.messages.ApplySnapshot;
 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.messages.RequestVote;
+import org.opendaylight.controller.cluster.raft.utils.InMemoryJournal;
+import org.opendaylight.controller.cluster.raft.utils.InMemorySnapshotStore;
+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.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.cohort3pc.ThreePhaseCommitCohortMessages;
 import org.opendaylight.controller.protobuff.messages.transaction.ShardTransactionMessages.CreateTransactionReply;
-import org.opendaylight.controller.sal.core.spi.data.DOMStoreThreePhaseCommitCohort;
-import org.opendaylight.controller.sal.core.spi.data.DOMStoreWriteTransaction;
+import org.opendaylight.yangtools.yang.common.QName;
 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.ContainerNode;
 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.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.DataTreeCandidate;
+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.DataTreeCandidates;
+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.impl.schema.ImmutableNodes;
+import org.opendaylight.yangtools.yang.data.impl.schema.builder.impl.ImmutableContainerNodeBuilder;
+import org.opendaylight.yangtools.yang.data.impl.schema.tree.InMemoryDataTreeFactory;
+import org.opendaylight.yangtools.yang.model.api.SchemaContext;
 import scala.concurrent.Await;
 import scala.concurrent.Future;
 import scala.concurrent.duration.FiniteDuration;
 
 public class ShardTest extends AbstractShardTest {
+    private static final QName CARS_QNAME = QName.create("urn:opendaylight:params:xml:ns:yang:controller:md:sal:dom:store:test:cars", "2014-03-13", "cars");
+
+    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";
+
+    final CountDownLatch recoveryComplete = new CountDownLatch(1);
+
+    protected Props newShardPropsWithRecoveryComplete() {
+
+        final Creator<Shard> creator = new Creator<Shard>() {
+            @Override
+            public Shard create() throws Exception {
+                return new Shard(shardID, Collections.<String,String>emptyMap(),
+                        newDatastoreContext(), SCHEMA_CONTEXT) {
+                    @Override
+                    protected void onRecoveryComplete() {
+                        try {
+                            super.onRecoveryComplete();
+                        } finally {
+                            recoveryComplete.countDown();
+                        }
+                    }
+                };
+            }
+        };
+        return Props.create(new DelegatingShardCreator(creator)).withDispatcher(Dispatchers.DefaultDispatcherId());
+    }
+
     @Test
     public void testRegisterChangeListener() throws Exception {
         new ShardTestKit(getSystem()) {{
-            TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
                     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 = getSystem().actorOf(DataChangeListener.props(listener),
                     "testRegisterChangeListener-DataChangeListener");
 
             shard.tell(new RegisterChangeListener(TestModel.TEST_PATH,
-                    dclActor.path(), AsyncDataBroker.DataChangeScope.BASE), getRef());
+                    dclActor, AsyncDataBroker.DataChangeScope.BASE), 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);
@@ -146,13 +195,17 @@ public class ShardTest extends AbstractShardTest {
             // 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(shardID, Collections.<String,String>emptyMap(),
+                            dataStoreContextBuilder.persistent(false).build(), SCHEMA_CONTEXT) {
                         @Override
                         public void onReceiveCommand(final Object message) throws Exception {
                             if(message instanceof ElectionTimeout && firstElectionTimeout) {
@@ -184,16 +237,16 @@ public class ShardTest extends AbstractShardTest {
                 }
             };
 
-            MockDataChangeListener listener = new MockDataChangeListener(1);
-            ActorRef dclActor = getSystem().actorOf(DataChangeListener.props(listener),
+            final MockDataChangeListener listener = new MockDataChangeListener(1);
+            final ActorRef dclActor = getSystem().actorOf(DataChangeListener.props(listener),
                     "testRegisterChangeListenerWhenNotLeaderInitially-DataChangeListener");
 
-            TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
                     Props.create(new DelegatingShardCreator(creator)),
                     "testRegisterChangeListenerWhenNotLeaderInitially");
 
             // Write initial data into the in-memory store.
-            YangInstanceIdentifier path = TestModel.TEST_PATH;
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
             writeToStore(shard, path, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
 
             // Wait until the shard receives the first ElectionTimeout message.
@@ -201,16 +254,16 @@ public class ShardTest extends AbstractShardTest {
                     onFirstElectionTimeout.await(5, TimeUnit.SECONDS));
 
             // Now send the RegisterChangeListener and wait for the reply.
-            shard.tell(new RegisterChangeListener(path, dclActor.path(),
+            shard.tell(new RegisterChangeListener(path, dclActor,
                     AsyncDataBroker.DataChangeScope.SUBTREE), 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 =
+            final FindLeaderReply findLeadeReply =
                     expectMsgClass(duration("5 seconds"), FindLeaderReply.class);
             assertNull("Expected the shard not to be the leader", findLeadeReply.getLeaderActor());
 
@@ -227,22 +280,126 @@ public class ShardTest extends AbstractShardTest {
         }};
     }
 
+    @Test
+    public void testRegisterDataTreeChangeListener() throws Exception {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps(), "testRegisterDataTreeChangeListener");
+
+            waitUntilLeader(shard);
+
+            shard.tell(new UpdateSchemaContext(SchemaContextHelper.full()), ActorRef.noSender());
+
+            final MockDataTreeChangeListener listener = new MockDataTreeChangeListener(1);
+            final ActorRef dclActor = getSystem().actorOf(DataTreeChangeListenerActor.props(listener),
+                    "testRegisterDataTreeChangeListener-DataTreeChangeListener");
+
+            shard.tell(new RegisterDataTreeChangeListener(TestModel.TEST_PATH, dclActor), getRef());
+
+            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\\/\\$.*"));
+
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
+            writeToStore(shard, path, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
+
+            listener.waitForChangeEvents();
+
+            dclActor.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @SuppressWarnings("serial")
+    @Test
+    public void testDataTreeChangeListenerNotifiedWhenNotTheLeaderOnRegistration() throws Exception {
+        new ShardTestKit(getSystem()) {{
+            final CountDownLatch onFirstElectionTimeout = new CountDownLatch(1);
+            final CountDownLatch onChangeListenerRegistered = new CountDownLatch(1);
+            final Creator<Shard> creator = new Creator<Shard>() {
+                boolean firstElectionTimeout = true;
+
+                @Override
+                public Shard create() throws Exception {
+                    return new Shard(shardID, Collections.<String,String>emptyMap(),
+                            dataStoreContextBuilder.persistent(false).build(), SCHEMA_CONTEXT) {
+                        @Override
+                        public void onReceiveCommand(final Object message) throws Exception {
+                            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();
+
+                                onFirstElectionTimeout.countDown();
+                            } else {
+                                super.onReceiveCommand(message);
+                            }
+                        }
+                    };
+                }
+            };
+
+            final MockDataTreeChangeListener listener = new MockDataTreeChangeListener(1);
+            final ActorRef dclActor = getSystem().actorOf(DataTreeChangeListenerActor.props(listener),
+                    "testDataTreeChangeListenerNotifiedWhenNotTheLeaderOnRegistration-DataChangeListener");
+
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    Props.create(new DelegatingShardCreator(creator)),
+                    "testDataTreeChangeListenerNotifiedWhenNotTheLeaderOnRegistration");
+
+            final YangInstanceIdentifier path = TestModel.TEST_PATH;
+            writeToStore(shard, path, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
+
+            assertEquals("Got first ElectionTimeout", true,
+                    onFirstElectionTimeout.await(5, TimeUnit.SECONDS));
+
+            shard.tell(new RegisterDataTreeChangeListener(path, dclActor), getRef());
+            final RegisterDataTreeChangeListenerReply reply = expectMsgClass(duration("5 seconds"),
+                    RegisterDataTreeChangeListenerReply.class);
+            assertNotNull("getListenerRegistratioznPath", reply.getListenerRegistrationPath());
+
+            shard.tell(new FindLeader(), getRef());
+            final FindLeaderReply findLeadeReply =
+                    expectMsgClass(duration("5 seconds"), FindLeaderReply.class);
+            assertNull("Expected the shard not to be the leader", findLeadeReply.getLeaderActor());
+
+            writeToStore(shard, path, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
+
+            onChangeListenerRegistered.countDown();
+
+            // TODO: investigate why we do not receive data chage events
+            listener.waitForChangeEvents();
+
+            dclActor.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
     @Test
     public void testCreateTransaction(){
         new ShardTestKit(getSystem()) {{
-            ActorRef shard = getSystem().actorOf(newShardProps(), "testCreateTransaction");
+            final ActorRef shard = getSystem().actorOf(newShardProps(), "testCreateTransaction");
 
             waitUntilLeader(shard);
 
             shard.tell(new UpdateSchemaContext(TestModel.createTestContext()), getRef());
 
             shard.tell(new CreateTransaction("txn-1",
-                    TransactionProxy.TransactionType.READ_ONLY.ordinal() ).toSerializable(), getRef());
+                    TransactionType.READ_ONLY.ordinal() ).toSerializable(), getRef());
 
-            CreateTransactionReply reply = expectMsgClass(duration("3 seconds"),
+            final CreateTransactionReply reply = expectMsgClass(duration("3 seconds"),
                     CreateTransactionReply.class);
 
-            String path = reply.getTransactionActorPath().toString();
+            final String path = reply.getTransactionActorPath().toString();
             assertTrue("Unexpected transaction path " + path,
                     path.contains("akka://test/user/testCreateTransaction/shard-txn-1"));
 
@@ -258,13 +415,13 @@ public class ShardTest extends AbstractShardTest {
             waitUntilLeader(shard);
 
             shard.tell(new CreateTransaction("txn-1",
-                    TransactionProxy.TransactionType.READ_ONLY.ordinal() , "foobar").toSerializable(),
+                    TransactionType.READ_ONLY.ordinal() , "foobar").toSerializable(),
                     getRef());
 
-            CreateTransactionReply reply = expectMsgClass(duration("3 seconds"),
+            final CreateTransactionReply reply = expectMsgClass(duration("3 seconds"),
                     CreateTransactionReply.class);
 
-            String path = reply.getTransactionActorPath().toString();
+            final String path = reply.getTransactionActorPath().toString();
             assertTrue("Unexpected transaction path " + path,
                     path.contains("akka://test/user/testCreateTransactionOnChain/shard-txn-1"));
 
@@ -279,7 +436,7 @@ public class ShardTest extends AbstractShardTest {
             final CountDownLatch recoveryComplete = new CountDownLatch(1);
             class TestShard extends Shard {
                 TestShard() {
-                    super(shardID, Collections.<ShardIdentifier, String>singletonMap(shardID, null),
+                    super(shardID, Collections.<String, String>singletonMap(shardID.toString(), null),
                             newDatastoreContext(), SCHEMA_CONTEXT);
                 }
 
@@ -309,8 +466,8 @@ public class ShardTest extends AbstractShardTest {
             assertEquals("Recovery complete", true,
                     Uninterruptibles.awaitUninterruptibly(recoveryComplete, 5, TimeUnit.SECONDS));
 
-            String address = "akka://foobar";
-            shard.underlyingActor().onReceiveCommand(new PeerAddressResolved(shardID, address));
+            final String address = "akka://foobar";
+            shard.underlyingActor().onReceiveCommand(new PeerAddressResolved(shardID.toString(), address));
 
             assertEquals("getPeerAddresses", address,
                     ((TestShard)shard.underlyingActor()).getPeerAddresses().get(shardID.toString()));
@@ -321,24 +478,28 @@ public class ShardTest extends AbstractShardTest {
 
     @Test
     public void testApplySnapshot() throws Exception {
-        TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(),
+        final TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(),
                 "testApplySnapshot");
 
-        InMemoryDOMDataStore store = new InMemoryDOMDataStore("OPER", MoreExecutors.sameThreadExecutor());
-        store.onGlobalContextUpdated(SCHEMA_CONTEXT);
+        final DataTree store = InMemoryDataTreeFactory.getInstance().create();
+        store.setSchemaContext(SCHEMA_CONTEXT);
+
+        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();
 
-        writeToStore(store, TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
+        writeToStore(store, TestModel.TEST_PATH, container);
 
-        YangInstanceIdentifier root = YangInstanceIdentifier.builder().build();
-        NormalizedNode<?,?> expected = readStore(store, root);
+        final YangInstanceIdentifier root = YangInstanceIdentifier.builder().build();
+        final NormalizedNode<?,?> expected = readStore(store, root);
 
-        ApplySnapshot applySnapshot = new ApplySnapshot(Snapshot.create(
-                SerializationUtils.serializeNormalizedNode(expected),
-                Collections.<ReplicatedLogEntry>emptyList(), 1, 2, 3, 4));
+        final Snapshot snapshot = Snapshot.create(SerializationUtils.serializeNormalizedNode(expected),
+                Collections.<ReplicatedLogEntry>emptyList(), 1, 2, 3, 4);
 
-        shard.underlyingActor().onReceiveCommand(applySnapshot);
+        shard.underlyingActor().getRaftActorSnapshotCohort().applySnapshot(snapshot.getState());
 
-        NormalizedNode<?,?> actual = readStore(shard, root);
+        final NormalizedNode<?,?> actual = readStore(shard, root);
 
         assertEquals("Root node", expected, actual);
 
@@ -348,73 +509,142 @@ public class ShardTest extends AbstractShardTest {
     @Test
     public void testApplyState() throws Exception {
 
-        TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(), "testApplyState");
+        final TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(), "testApplyState");
 
-        NormalizedNode<?, ?> node = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+        final NormalizedNode<?, ?> node = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
 
-        ApplyState applyState = new ApplyState(null, "test", new ReplicatedLogImplEntry(1, 2,
+        final ApplyState applyState = new ApplyState(null, "test", new ReplicatedLogImplEntry(1, 2,
                 newModificationPayload(new WriteModification(TestModel.TEST_PATH, node))));
 
         shard.underlyingActor().onReceiveCommand(applyState);
 
-        NormalizedNode<?,?> actual = readStore(shard, TestModel.TEST_PATH);
+        final NormalizedNode<?,?> actual = readStore(shard, TestModel.TEST_PATH);
         assertEquals("Applied state", node, actual);
 
         shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
     }
 
     @Test
-    public void testRecovery() throws Exception {
+    public void testApplyStateWithCandidatePayload() throws Exception {
 
-        // Set up the InMemorySnapshotStore.
+        final TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardPropsWithRecoveryComplete(), "testApplyState");
+
+        recoveryComplete.await(5,  TimeUnit.SECONDS);
 
-        InMemoryDOMDataStore testStore = InMemoryDOMDataStoreFactory.create("Test", null, null);
-        testStore.onGlobalContextUpdated(SCHEMA_CONTEXT);
+        final NormalizedNode<?, ?> node = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
+        final DataTreeCandidate candidate = DataTreeCandidates.fromNormalizedNode(TestModel.TEST_PATH, node);
+
+        final ApplyState applyState = new ApplyState(null, "test", new ReplicatedLogImplEntry(1, 2,
+                DataTreeCandidatePayload.create(candidate)));
+
+        shard.underlyingActor().onReceiveCommand(applyState);
+
+        final NormalizedNode<?,?> actual = readStore(shard, TestModel.TEST_PATH);
+        assertEquals("Applied state", node, actual);
+
+        shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+    }
+
+    DataTree setupInMemorySnapshotStore() throws DataValidationFailedException {
+        final DataTree testStore = InMemoryDataTreeFactory.getInstance().create();
+        testStore.setSchemaContext(SCHEMA_CONTEXT);
 
         writeToStore(testStore, TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
 
-        NormalizedNode<?, ?> root = readStore(testStore, YangInstanceIdentifier.builder().build());
+        final NormalizedNode<?, ?> root = readStore(testStore, YangInstanceIdentifier.builder().build());
 
         InMemorySnapshotStore.addSnapshot(shardID.toString(), Snapshot.create(
                 SerializationUtils.serializeNormalizedNode(root),
                 Collections.<ReplicatedLogEntry>emptyList(), 0, 1, -1, -1));
+        return testStore;
+    }
+
+    private static DataTreeCandidatePayload payloadForModification(final DataTree source, final DataTreeModification mod) throws DataValidationFailedException {
+        source.validate(mod);
+        final DataTreeCandidate candidate = source.prepare(mod);
+        source.commit(candidate);
+        return DataTreeCandidatePayload.create(candidate);
+    }
+
+    @Test
+    public void testDataTreeCandidateRecovery() throws Exception {
+        // Set up the InMemorySnapshotStore.
+        final DataTree source = setupInMemorySnapshotStore();
+
+        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, newModificationPayload(
+        final int nListEntries = 16;
+        final Set<Integer> listEntryKeys = new HashSet<>();
+
+        // Add some ModificationPayload entries
+        for (int i = 1; i <= nListEntries; i++) {
+            listEntryKeys.add(Integer.valueOf(i));
+
+            final YangInstanceIdentifier path = YangInstanceIdentifier.builder(TestModel.OUTER_LIST_PATH)
+                    .nodeWithKey(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, i).build();
+
+            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)));
+        }
+
+        InMemoryJournal.addEntry(shardID.toString(), nListEntries + 2,
+                new ApplyJournalEntries(nListEntries));
+
+        testRecovery(listEntryKeys);
+    }
+
+    @Test
+    public void testModicationRecovery() throws Exception {
+
+        // Set up the InMemorySnapshotStore.
+        setupInMemorySnapshotStore();
+
+        // Set up the InMemoryJournal.
+
+        InMemoryJournal.addEntry(shardID.toString(), 0, DUMMY_DATA);
+
+        InMemoryJournal.addEntry(shardID.toString(), 1, new ReplicatedLogImplEntry(0, 1, newModificationPayload(
                   new WriteModification(TestModel.OUTER_LIST_PATH,
                           ImmutableNodes.mapNodeBuilder(TestModel.OUTER_LIST_QNAME).build()))));
 
-        int nListEntries = 16;
-        Set<Integer> listEntryKeys = new HashSet<>();
+        final int nListEntries = 16;
+        final Set<Integer> listEntryKeys = new HashSet<>();
 
         // Add some ModificationPayload entries
         for(int i = 1; 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,
+            final Modification mod = new MergeModification(path,
                     ImmutableNodes.mapEntry(TestModel.OUTER_LIST_QNAME, TestModel.ID_QNAME, i));
-            InMemoryJournal.addEntry(shardID.toString(), i, new ReplicatedLogImplEntry(i, 1,
+            InMemoryJournal.addEntry(shardID.toString(), i + 1, new ReplicatedLogImplEntry(i, 1,
                     newModificationPayload(mod)));
         }
 
-        InMemoryJournal.addEntry(shardID.toString(), nListEntries + 1,
+        InMemoryJournal.addEntry(shardID.toString(), nListEntries + 2,
                 new ApplyJournalEntries(nListEntries));
 
         testRecovery(listEntryKeys);
     }
 
-    private ModificationPayload newModificationPayload(final Modification... mods) throws IOException {
-        MutableCompositeModification compMod = new MutableCompositeModification();
-        for(Modification mod: mods) {
+    private static ModificationPayload newModificationPayload(final Modification... mods) throws IOException {
+        final MutableCompositeModification compMod = new MutableCompositeModification();
+        for(final Modification mod: mods) {
             compMod.addModification(mod);
         }
 
         return new ModificationPayload(compMod);
     }
 
-    @SuppressWarnings({ "unchecked" })
     @Test
     public void testConcurrentThreePhaseCommits() throws Throwable {
         new ShardTestKit(getSystem()) {{
@@ -424,31 +654,31 @@ public class ShardTest extends AbstractShardTest {
 
             waitUntilLeader(shard);
 
-            // Setup 3 simulated transactions with mock cohorts backed by real cohorts.
+         // 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);
 
@@ -456,35 +686,35 @@ public class ShardTest extends AbstractShardTest {
             // by the ShardTransaction.
 
             shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
-                    cohort1, modification1, true), getRef());
-            ReadyTransactionReply readyReply = ReadyTransactionReply.fromSerializable(
-                    expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS));
+                    cohort1, modification1, true, false), 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(
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
                     expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
             assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
             // Send the ForwardedReadyTransaction for the next 2 Tx's.
 
             shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+                    cohort2, modification2, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             shard.tell(new ForwardedReadyTransaction(transactionID3, CURRENT_VERSION,
-                    cohort3, modification3, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+                    cohort3, modification3, true, false), 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,
+            final Future<Object> canCommitFuture1 = Patterns.ask(shard,
                     new CanCommitTransaction(transactionID2).toSerializable(), timeout);
 
-            Future<Object> canCommitFuture2 = Patterns.ask(shard,
+            final Future<Object> canCommitFuture2 = Patterns.ask(shard,
                     new CanCommitTransaction(transactionID3).toSerializable(), timeout);
 
             // Send the CommitTransaction message for the first Tx. After it completes, it should
@@ -513,7 +743,7 @@ public class ShardTest extends AbstractShardTest {
                         try {
                             assertEquals("Commit response type", expRespType, resp.getClass());
                             onSuccess(resp);
-                        } catch (Exception e) {
+                        } catch (final Exception e) {
                             caughtEx.set(e);
                         }
                     }
@@ -545,11 +775,11 @@ public class ShardTest extends AbstractShardTest {
 
                 @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,
+                    final Future<Object> commitFuture = Patterns.ask(shard,
                             new CommitTransaction(transactionID).toSerializable(), timeout);
                     commitFuture.onComplete(new OnCommitFutureComplete(), getSystem().dispatcher());
                 }
@@ -561,7 +791,7 @@ public class ShardTest extends AbstractShardTest {
             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();
@@ -569,7 +799,7 @@ public class ShardTest extends AbstractShardTest {
 
             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();
@@ -582,20 +812,442 @@ public class ShardTest extends AbstractShardTest {
 
             // 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);
+            verifyOuterListEntry(shard, 1);
+
+            verifyLastApplied(shard, 2);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    private static BatchedModifications newBatchedModifications(final String transactionID, final YangInstanceIdentifier path,
+            final NormalizedNode<?, ?> data, final boolean ready, final boolean doCommitOnReady, final int messagesSent) {
+        return newBatchedModifications(transactionID, null, path, data, ready, doCommitOnReady, messagesSent);
+    }
+
+    private static BatchedModifications newBatchedModifications(final String transactionID, final String transactionChainID,
+            final YangInstanceIdentifier path, final NormalizedNode<?, ?> data, final boolean ready, final boolean doCommitOnReady,
+            final int messagesSent) {
+        final BatchedModifications batched = new BatchedModifications(transactionID, CURRENT_VERSION, transactionChainID);
+        batched.addModification(new WriteModification(path, data));
+        batched.setReady(ready);
+        batched.setDoCommitOnReady(doCommitOnReady);
+        batched.setTotalMessagesSent(messagesSent);
+        return batched;
+    }
+
+    @Test
+    public void testBatchedModificationsWithNoCommitOnReady() throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testBatchedModificationsWithNoCommitOnReady");
+
+            waitUntilLeader(shard);
+
+            final String transactionID = "tx";
+            final FiniteDuration duration = duration("5 seconds");
+
+            final AtomicReference<ShardDataTreeCohort> mockCohort = new AtomicReference<>();
+            final ShardCommitCoordinator.CohortDecorator cohortDecorator = new ShardCommitCoordinator.CohortDecorator() {
+                @Override
+                public ShardDataTreeCohort decorate(final String txID, final ShardDataTreeCohort actual) {
+                    if(mockCohort.get() == null) {
+                        mockCohort.set(createDelegatingMockCohort("cohort", actual));
+                    }
+
+                    return mockCohort.get();
+                }
+            };
+
+            shard.underlyingActor().getCommitCoordinator().setCohortDecorator(cohortDecorator);
+
+            // Send a BatchedModifications to start a transaction.
+
+            shard.tell(newBatchedModifications(transactionID, TestModel.TEST_PATH,
+                    ImmutableNodes.containerNode(TestModel.TEST_QNAME), false, false, 1), getRef());
+            expectMsgClass(duration, BatchedModificationsReply.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());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+            // Send the CanCommitTransaction message.
+
+            shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+
+            final InOrder inOrder = inOrder(mockCohort.get());
+            inOrder.verify(mockCohort.get()).canCommit();
+            inOrder.verify(mockCohort.get()).preCommit();
+            inOrder.verify(mockCohort.get()).commit();
+
+            // Verify data in the data store.
+
+            verifyOuterListEntry(shard, 1);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @Test
+    public void testBatchedModificationsWithCommitOnReady() throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testBatchedModificationsWithCommitOnReady");
+
+            waitUntilLeader(shard);
+
+            final String transactionID = "tx";
+            final FiniteDuration duration = duration("5 seconds");
+
+            final AtomicReference<ShardDataTreeCohort> mockCohort = new AtomicReference<>();
+            final ShardCommitCoordinator.CohortDecorator cohortDecorator = new ShardCommitCoordinator.CohortDecorator() {
+                @Override
+                public ShardDataTreeCohort decorate(final String txID, final ShardDataTreeCohort actual) {
+                    if(mockCohort.get() == null) {
+                        mockCohort.set(createDelegatingMockCohort("cohort", actual));
+                    }
+
+                    return mockCohort.get();
+                }
+            };
+
+            shard.underlyingActor().getCommitCoordinator().setCohortDecorator(cohortDecorator);
+
+            // Send a BatchedModifications to start a transaction.
+
+            shard.tell(newBatchedModifications(transactionID, TestModel.TEST_PATH,
+                    ImmutableNodes.containerNode(TestModel.TEST_QNAME), false, false, 1), getRef());
+            expectMsgClass(duration, BatchedModificationsReply.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, true, 3), getRef());
+
+            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+
+            final InOrder inOrder = inOrder(mockCohort.get());
+            inOrder.verify(mockCohort.get()).canCommit();
+            inOrder.verify(mockCohort.get()).preCommit();
+            inOrder.verify(mockCohort.get()).commit();
+
+            // Verify data in the data store.
+
+            verifyOuterListEntry(shard, 1);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @Test(expected=IllegalStateException.class)
+    public void testBatchedModificationsReadyWithIncorrectTotalMessageCount() throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testBatchedModificationsReadyWithIncorrectTotalMessageCount");
+
+            waitUntilLeader(shard);
+
+            final String transactionID = "tx1";
+            final BatchedModifications batched = new BatchedModifications(transactionID, DataStoreVersions.CURRENT_VERSION, null);
+            batched.setReady(true);
+            batched.setTotalMessagesSent(2);
+
+            shard.tell(batched, getRef());
+
+            final Failure failure = expectMsgClass(duration("5 seconds"), akka.actor.Status.Failure.class);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+
+            if(failure != null) {
+                throw failure.cause();
+            }
+        }};
+    }
+
+    @Test
+    public void testBatchedModificationsWithOperationFailure() throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testBatchedModificationsWithOperationFailure");
+
+            waitUntilLeader(shard);
+
+            // 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.
+
+            String transactionID = "tx1";
+
+            ContainerNode invalidData = ImmutableContainerNodeBuilder.create().withNodeIdentifier(
+                    new YangInstanceIdentifier.NodeIdentifier(TestModel.TEST_QNAME)).
+                        withChild(ImmutableNodes.leafNode(TestModel.JUNK_QNAME, "junk")).build();
+
+            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);
+
+            Throwable cause = failure.cause();
+
+            batched = new BatchedModifications(transactionID, DataStoreVersions.CURRENT_VERSION, null);
+            batched.setReady(true);
+            batched.setTotalMessagesSent(2);
+
+            shard.tell(batched, getRef());
+
+            failure = expectMsgClass(duration("5 seconds"), akka.actor.Status.Failure.class);
+            assertEquals("Failure cause", cause, failure.cause());
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @SuppressWarnings("unchecked")
+    private static void verifyOuterListEntry(final TestActorRef<Shard> shard, final Object expIDValue) throws Exception {
+        final 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);
+        final Object entry = ((Iterable<Object>)outerList.getValue()).iterator().next();
+        assertTrue(TestModel.OUTER_LIST_QNAME.getLocalName() + " entry is not MapEntryNode",
+                entry instanceof MapEntryNode);
+        final MapEntryNode mapEntry = (MapEntryNode)entry;
+        final 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", expIDValue, idLeaf.get().getValue());
+    }
+
+    @Test
+    public void testBatchedModificationsOnTransactionChain() throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testBatchedModificationsOnTransactionChain");
+
+            waitUntilLeader(shard);
+
+            final String transactionChainID = "txChain";
+            final String transactionID1 = "tx1";
+            final String transactionID2 = "tx2";
+
+            final FiniteDuration duration = duration("5 seconds");
+
+            // 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).toSerializable(), getRef());
+
+            final CreateTransactionReply createReply = expectMsgClass(duration("3 seconds"), CreateTransactionReply.class);
+
+            getSystem().actorSelection(createReply.getTransactionActorPath()).tell(new ReadData(path), 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).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+            shard.tell(new CommitTransaction(transactionID1).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+
+            // Verify data in the data store.
+
+            final NormalizedNode<?, ?> actualNode = readStore(shard, path);
+            assertEquals("Stored node", containerNode, actualNode);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @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(shardID, Collections.<String,String>emptyMap(),
+                            newDatastoreContext(), SCHEMA_CONTEXT) {
+                        @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 = TestActorRef.create(getSystem(),
+                    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);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @Test
+    public void testForwardedReadyTransactionWithImmediateCommit() throws Exception{
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testForwardedReadyTransactionWithImmediateCommit");
+
+            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");
+
+            // Simulate the ForwardedReadyTransaction messages that would be sent
+            // by the ShardTransaction.
+
+            shard.tell(new ForwardedReadyTransaction(transactionID, CURRENT_VERSION,
+                    cohort, modification, true, true), getRef());
+
+            expectMsgClass(duration, ThreePhaseCommitCohortMessages.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);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @Test
+    public void testReadyLocalTransactionWithImmediateCommit() throws Exception{
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testReadyLocalTransactionWithImmediateCommit");
+
+            waitUntilLeader(shard);
+
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
+
+            final DataTreeModification modification = dataStore.getDataTree().takeSnapshot().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.SERIALIZABLE_CLASS);
+
+            final NormalizedNode<?, ?> actualNode = readStore(shard, TestModel.OUTER_LIST_PATH);
+            assertEquals(TestModel.OUTER_LIST_QNAME.getLocalName(), mergeData, actualNode);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @Test
+    public void testReadyLocalTransactionWithThreePhaseCommit() throws Exception{
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testReadyLocalTransactionWithThreePhaseCommit");
+
+            waitUntilLeader(shard);
+
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
+
+            final DataTreeModification modification = dataStore.getDataTree().takeSnapshot().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).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+
+            // Send the CanCommitTransaction message.
+
+            shard.tell(new CommitTransaction(txId).toSerializable(), getRef());
+            expectMsgClass(CommitTransactionReply.SERIALIZABLE_CLASS);
+
+            final NormalizedNode<?, ?> actualNode = readStore(shard, TestModel.OUTER_LIST_PATH);
+            assertEquals(TestModel.OUTER_LIST_QNAME.getLocalName(), mergeData, actualNode);
 
             shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
@@ -607,33 +1259,33 @@ public class ShardTest extends AbstractShardTest {
         new ShardTestKit(getSystem()) {{
             final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testCommitPhaseFailure");
+                    "testCommitWithPersistenceDisabled");
 
             waitUntilLeader(shard);
 
-            InMemoryDOMDataStore dataStore = shard.underlyingActor().getDataStore();
+            final ShardDataTree dataStore = shard.underlyingActor().getDataStore();
 
             // Setup a simulated transactions with a mock cohort.
 
-            String transactionID = "tx";
-            MutableCompositeModification modification = new MutableCompositeModification();
-            NormalizedNode<?, ?> containerNode = ImmutableNodes.containerNode(TestModel.TEST_QNAME);
-            DOMStoreThreePhaseCommitCohort cohort = setupMockWriteTransaction("cohort", dataStore,
+            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);
 
-            FiniteDuration duration = duration("5 seconds");
+            final FiniteDuration duration = duration("5 seconds");
 
             // 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);
+                    cohort, modification, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             // Send the CanCommitTransaction message.
 
             shard.tell(new CanCommitTransaction(transactionID).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
                     expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
             assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
@@ -642,18 +1294,37 @@ public class ShardTest extends AbstractShardTest {
             shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
             expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
 
-            InOrder inOrder = inOrder(cohort);
+            final InOrder inOrder = inOrder(cohort);
             inOrder.verify(cohort).canCommit();
             inOrder.verify(cohort).preCommit();
             inOrder.verify(cohort).commit();
 
-            NormalizedNode<?, ?> actualNode = readStore(shard, TestModel.TEST_PATH);
+            final NormalizedNode<?, ?> actualNode = readStore(shard, TestModel.TEST_PATH);
             assertEquals(TestModel.TEST_QNAME.getLocalName(), containerNode, actualNode);
 
             shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
     }
 
+    private static DataTreeCandidateTip mockCandidate(final String name) {
+        final DataTreeCandidateTip mockCandidate = mock(DataTreeCandidateTip.class, name);
+        final DataTreeCandidateNode mockCandidateNode = mock(DataTreeCandidateNode.class, name + "-node");
+        doReturn(ModificationType.WRITE).when(mockCandidateNode).getModificationType();
+        doReturn(Optional.of(ImmutableNodes.containerNode(CARS_QNAME))).when(mockCandidateNode).getDataAfter();
+        doReturn(YangInstanceIdentifier.builder().build()).when(mockCandidate).getRootPath();
+        doReturn(mockCandidateNode).when(mockCandidate).getRootNode();
+        return mockCandidate;
+    }
+
+    private static DataTreeCandidateTip mockUnmodifiedCandidate(final String name) {
+        final DataTreeCandidateTip mockCandidate = mock(DataTreeCandidateTip.class, name);
+        final DataTreeCandidateNode mockCandidateNode = mock(DataTreeCandidateNode.class, name + "-node");
+        doReturn(ModificationType.UNMODIFIED).when(mockCandidateNode).getModificationType();
+        doReturn(YangInstanceIdentifier.builder().build()).when(mockCandidate).getRootPath();
+        doReturn(mockCandidateNode).when(mockCandidate).getRootNode();
+        return mockCandidate;
+    }
+
     @Test
     public void testCommitWhenTransactionHasNoModifications(){
         // Note that persistence is enabled which would normally result in the entry getting written to the journal
@@ -666,43 +1337,47 @@ public class ShardTest extends AbstractShardTest {
 
                 waitUntilLeader(shard);
 
-                String transactionID = "tx1";
-                MutableCompositeModification modification = new MutableCompositeModification();
-                DOMStoreThreePhaseCommitCohort cohort = mock(DOMStoreThreePhaseCommitCohort.class, "cohort1");
+                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();
 
-                FiniteDuration duration = duration("5 seconds");
+                final FiniteDuration duration = duration("5 seconds");
 
                 // 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);
+                        cohort, modification, true, false), getRef());
+                expectMsgClass(duration, ReadyTransactionReply.class);
 
                 // Send the CanCommitTransaction message.
 
                 shard.tell(new CanCommitTransaction(transactionID).toSerializable(), getRef());
-                CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
                         expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
                 assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
                 shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
                 expectMsgClass(duration, ThreePhaseCommitCohortMessages.CommitTransactionReply.class);
 
-                InOrder inOrder = inOrder(cohort);
+                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,shard.underlyingActor().getShardMBean().getCommittedTransactionsCount());
+                assertEquals(1,shardStats.getCommittedTransactionsCount());
 
                 // Commit index should not advance because this does not go into the journal
-                assertEquals(-1, shard.underlyingActor().getShardMBean().getCommitIndex());
+                assertEquals(-1, shardStats.getCommitIndex());
 
                 shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
 
@@ -720,100 +1395,180 @@ public class ShardTest extends AbstractShardTest {
 
                 waitUntilLeader(shard);
 
-                String transactionID = "tx1";
-                MutableCompositeModification modification = new MutableCompositeModification();
+                final String transactionID = "tx1";
+                final MutableCompositeModification modification = new MutableCompositeModification();
                 modification.addModification(new DeleteModification(YangInstanceIdentifier.builder().build()));
-                DOMStoreThreePhaseCommitCohort cohort = mock(DOMStoreThreePhaseCommitCohort.class, "cohort1");
+                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();
 
-                FiniteDuration duration = duration("5 seconds");
+                final FiniteDuration duration = duration("5 seconds");
 
                 // 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);
+                        cohort, modification, true, false), getRef());
+                expectMsgClass(duration, ReadyTransactionReply.class);
 
                 // Send the CanCommitTransaction message.
 
                 shard.tell(new CanCommitTransaction(transactionID).toSerializable(), getRef());
-                CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
                         expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
                 assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
-                shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
-                expectMsgClass(duration, ThreePhaseCommitCohortMessages.CommitTransactionReply.class);
+                shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
+                expectMsgClass(duration, ThreePhaseCommitCohortMessages.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());
+
+                shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+
+            }
+        };
+    }
+
+    @Test
+    public void testCommitPhaseFailure() throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testCommitPhaseFailure");
+
+            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 IllegalStateException("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);
+
+            // Simulate the ForwardedReadyTransaction messages that would be sent
+            // by the ShardTransaction.
+
+            shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
+                    cohort1, modification1, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
+                    cohort2, modification2, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // Send the CanCommitTransaction message for the first Tx.
+
+            shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_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).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).toSerializable(), getRef());
+            expectMsgClass(duration, akka.actor.Status.Failure.class);
 
-                InOrder inOrder = inOrder(cohort);
-                inOrder.verify(cohort).canCommit();
-                inOrder.verify(cohort).preCommit();
-                inOrder.verify(cohort).commit();
+            // Wait for the 2nd Tx to complete the canCommit phase.
 
-                // Use MBean for verification
-                // Committed transaction count should increase as usual
-                assertEquals(1,shard.underlyingActor().getShardMBean().getCommittedTransactionsCount());
+            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());
 
-                // Commit index should advance as we do not have an empty modification
-                assertEquals(0, shard.underlyingActor().getShardMBean().getCommitIndex());
+            assertEquals("2nd CanCommit complete", true, latch.await(5, TimeUnit.SECONDS));
 
-                shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+            final InOrder inOrder = inOrder(cohort1, cohort2);
+            inOrder.verify(cohort1).canCommit();
+            inOrder.verify(cohort1).preCommit();
+            inOrder.verify(cohort1).commit();
+            inOrder.verify(cohort2).canCommit();
 
-            }
-        };
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
     }
 
     @Test
-    public void testCommitPhaseFailure() throws Throwable {
+    public void testPreCommitPhaseFailure() throws Throwable {
         new ShardTestKit(getSystem()) {{
             final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testCommitPhaseFailure");
+                    "testPreCommitPhaseFailure");
 
             waitUntilLeader(shard);
 
-            // Setup 2 simulated transactions with mock cohorts. The first one fails in the
-            // commit phase.
-
-            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).preCommit();
-            doReturn(Futures.immediateFailedFuture(new IllegalStateException("mock"))).when(cohort1).commit();
+            doReturn(Futures.immediateFailedFuture(new IllegalStateException("mock"))).when(cohort1).preCommit();
 
-            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);
+                    cohort1, modification1, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+                    cohort2, modification2, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             // Send the CanCommitTransaction message for the first Tx.
 
             shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
                     expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_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,
+            final Future<Object> canCommitFuture = Patterns.ask(shard,
                     new CanCommitTransaction(transactionID2).toSerializable(), timeout);
 
             // Send the CommitTransaction message for the first Tx. This should send back an error
@@ -834,10 +1589,9 @@ public class ShardTest extends AbstractShardTest {
 
             assertEquals("2nd CanCommit complete", true, latch.await(5, TimeUnit.SECONDS));
 
-            InOrder inOrder = inOrder(cohort1, cohort2);
+            final InOrder inOrder = inOrder(cohort1, cohort2);
             inOrder.verify(cohort1).canCommit();
             inOrder.verify(cohort1).preCommit();
-            inOrder.verify(cohort1).commit();
             inOrder.verify(cohort2).canCommit();
 
             shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
@@ -845,78 +1599,193 @@ public class ShardTest extends AbstractShardTest {
     }
 
     @Test
-    public void testPreCommitPhaseFailure() throws Throwable {
+    public void testCanCommitPhaseFailure() throws Throwable {
         new ShardTestKit(getSystem()) {{
             final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testPreCommitPhaseFailure");
+                    "testCanCommitPhaseFailure");
 
             waitUntilLeader(shard);
 
-            String transactionID = "tx1";
-            MutableCompositeModification modification = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort = mock(DOMStoreThreePhaseCommitCohort.class, "cohort1");
+            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(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
+                    cohort, modification, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // Send the CanCommitTransaction message.
+
+            shard.tell(new CanCommitTransaction(transactionID1).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();
-            doReturn(Futures.immediateFailedFuture(new IllegalStateException("mock"))).when(cohort).preCommit();
 
-            FiniteDuration duration = duration("5 seconds");
+            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
+                    cohort, modification, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            shard.tell(new CanCommitTransaction(transactionID2).toSerializable(), getRef());
+            final CanCommitTransactionReply reply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            assertEquals("getCanCommit", true, reply.getCanCommit());
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @Test
+    public void testCanCommitPhaseFalseResponse() throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testCanCommitPhaseFalseResponse");
+
+            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();
 
             // 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);
+            shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
+                    cohort, modification, true, false), 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));
-            assertEquals("Can commit", true, canCommitReply.getCanCommit());
+            shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
+            CanCommitTransactionReply reply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            assertEquals("getCanCommit", false, reply.getCanCommit());
 
-            // Send the CommitTransaction message. This should send back an error
-            // for preCommit failure.
+            // Send another can commit to ensure the failed one got cleaned up.
 
-            shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
-            expectMsgClass(duration, akka.actor.Status.Failure.class);
+            reset(cohort);
 
-            InOrder inOrder = inOrder(cohort);
-            inOrder.verify(cohort).canCommit();
-            inOrder.verify(cohort).preCommit();
+            final String transactionID2 = "tx2";
+            doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).canCommit();
+
+            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
+                    cohort, modification, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            shard.tell(new CanCommitTransaction(transactionID2).toSerializable(), getRef());
+            reply = CanCommitTransactionReply.fromSerializable(
+                    expectMsgClass(CanCommitTransactionReply.SERIALIZABLE_CLASS));
+            assertEquals("getCanCommit", true, reply.getCanCommit());
 
             shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
     }
 
     @Test
-    public void testCanCommitPhaseFailure() throws Throwable {
+    public void testImmediateCommitWithCanCommitPhaseFailure() throws Throwable {
         new ShardTestKit(getSystem()) {{
             final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
                     newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
-                    "testCanCommitPhaseFailure");
+                    "testImmediateCommitWithCanCommitPhaseFailure");
 
             waitUntilLeader(shard);
 
             final FiniteDuration duration = duration("5 seconds");
 
-            String transactionID = "tx1";
-            MutableCompositeModification modification = new MutableCompositeModification();
-            DOMStoreThreePhaseCommitCohort cohort = mock(DOMStoreThreePhaseCommitCohort.class, "cohort1");
+            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(new ForwardedReadyTransaction(transactionID, CURRENT_VERSION,
-                    cohort, modification, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+            shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
+                    cohort, modification, true, true), getRef());
 
-            // Send the CanCommitTransaction message.
+            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(candidate).when(cohort).getCandidate();
+
+            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
+                    cohort, modification, true, true), getRef());
+
+            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @Test
+    public void testImmediateCommitWithCanCommitPhaseFalseResponse() throws Throwable {
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    newShardProps().withDispatcher(Dispatchers.DefaultDispatcherId()),
+                    "testImmediateCommitWithCanCommitPhaseFalseResponse");
+
+            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();
+
+            // Simulate the ForwardedReadyTransaction messages that would be sent
+            // by the ShardTransaction.
+
+            shard.tell(new ForwardedReadyTransaction(transactionID, CURRENT_VERSION,
+                    cohort, modification, true, true), getRef());
 
-            shard.tell(new CanCommitTransaction(transactionID).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();
+            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(candidate).when(cohort).getCandidate();
+
+            shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
+                    cohort, modification, true, true), getRef());
+
+            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+
             shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
     }
@@ -931,14 +1800,14 @@ public class ShardTest extends AbstractShardTest {
             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>>() {
+            final Function<ShardDataTreeCohort, ListenableFuture<Void>> preCommit =
+                          new Function<ShardDataTreeCohort, ListenableFuture<Void>>() {
                 @Override
-                public ListenableFuture<Void> apply(final DOMStoreThreePhaseCommitCohort cohort) {
-                    ListenableFuture<Void> preCommitFuture = cohort.preCommit();
+                public ListenableFuture<Void> apply(final ShardDataTreeCohort 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.
@@ -954,24 +1823,24 @@ public class ShardTest extends AbstractShardTest {
                 }
             };
 
-            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);
+                    cohort, modification, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             shard.tell(new CanCommitTransaction(transactionID).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
                     expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS));
             assertEquals("Can commit", true, canCommitReply.getCanCommit());
 
             shard.tell(new CommitTransaction(transactionID).toSerializable(), getRef());
             expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_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
@@ -995,7 +1864,7 @@ public class ShardTest extends AbstractShardTest {
 
             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,
@@ -1003,9 +1872,9 @@ public class ShardTest extends AbstractShardTest {
 
             // 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),
@@ -1013,11 +1882,11 @@ public class ShardTest extends AbstractShardTest {
 
             // 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);
@@ -1025,12 +1894,12 @@ public class ShardTest extends AbstractShardTest {
             // Ready the Tx's
 
             shard.tell(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
-                    cohort1, modification1, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+                    cohort1, modification1, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+                    cohort2, modification2, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             // canCommit 1st Tx. We don't send the commit so it should timeout.
 
@@ -1042,12 +1911,17 @@ public class ShardTest extends AbstractShardTest {
             shard.tell(new CanCommitTransaction(transactionID2).toSerializable(), getRef());
             expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS);
 
+            // Try to commit the 1st Tx - should fail as it's not the current Tx.
+
+            shard.tell(new CommitTransaction(transactionID1).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);
 
-            NormalizedNode<?, ?> node = readStore(shard, listNodePath);
+            final NormalizedNode<?, ?> node = readStore(shard, listNodePath);
             assertNotNull(listNodePath + " not found", node);
 
             shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
@@ -1056,7 +1930,7 @@ public class ShardTest extends AbstractShardTest {
 
     @Test
     public void testTransactionCommitQueueCapacityExceeded() throws Throwable {
-        dataStoreContextBuilder.shardTransactionCommitQueueCapacity(1);
+        dataStoreContextBuilder.shardTransactionCommitQueueCapacity(2);
 
         new ShardTestKit(getSystem()) {{
             final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
@@ -1067,38 +1941,40 @@ public class ShardTest extends AbstractShardTest {
 
             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);
+                    cohort1, modification1, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+                    cohort2, modification2, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.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);
+                    cohort3, modification3, true, false), getRef());
+            expectMsgClass(duration, akka.actor.Status.Failure.class);
 
             // canCommit 1st Tx.
 
@@ -1118,6 +1994,126 @@ public class ShardTest extends AbstractShardTest {
         }};
     }
 
+    @Test
+    public void testTransactionCommitWithPriorExpiredCohortEntries() throws Throwable {
+        dataStoreContextBuilder.shardCommitQueueExpiryTimeoutInMillis(1300).shardTransactionCommitTimeoutInSeconds(1);
+
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    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(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
+                    cohort1, modification1, true, false), 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(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
+                    cohort2, modification2, true, false), 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(new ForwardedReadyTransaction(transactionID3, CURRENT_VERSION,
+                    cohort3, modification3, true, false), 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).toSerializable(), getRef());
+            expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_CLASS);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
+    @Test
+    public void testTransactionCommitWithSubsequentExpiredCohortEntry() throws Throwable {
+        dataStoreContextBuilder.shardCommitQueueExpiryTimeoutInMillis(1300).shardTransactionCommitTimeoutInSeconds(1);
+
+        new ShardTestKit(getSystem()) {{
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+                    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(new ForwardedReadyTransaction(transactionID1, CURRENT_VERSION,
+                    cohort1, modification1, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // CanCommit the first one so it's the current in-progress CohortEntry.
+
+            shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
+            expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_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(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
+                    cohort2, modification2, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
+
+            // Ready the third Tx.
+
+            final String transactionID3 = "tx3";
+            final DataTreeModification modification3 = dataStore.getDataTree().takeSnapshot().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).toSerializable(), getRef());
+            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+
+            // Expect commit reply from the third Tx.
+
+            expectMsgClass(duration, CommitTransactionReply.SERIALIZABLE_CLASS);
+
+            final NormalizedNode<?, ?> node = readStore(shard, TestModel.TEST2_PATH);
+            assertNotNull(TestModel.TEST2_PATH + " not found", node);
+
+            shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
+        }};
+    }
+
     @Test
     public void testCanCommitBeforeReadyFailure() throws Throwable {
         new ShardTestKit(getSystem()) {{
@@ -1143,42 +2139,42 @@ public class ShardTest extends AbstractShardTest {
 
             // 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);
+                    cohort1, modification1, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             shard.tell(new ForwardedReadyTransaction(transactionID2, CURRENT_VERSION,
-                    cohort2, modification2, true), getRef());
-            expectMsgClass(duration, ReadyTransactionReply.SERIALIZABLE_CLASS);
+                    cohort2, modification2, true, false), getRef());
+            expectMsgClass(duration, ReadyTransactionReply.class);
 
             // Send the CanCommitTransaction message for the first Tx.
 
             shard.tell(new CanCommitTransaction(transactionID1).toSerializable(), getRef());
-            CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
+            final CanCommitTransactionReply canCommitReply = CanCommitTransactionReply.fromSerializable(
                     expectMsgClass(duration, CanCommitTransactionReply.SERIALIZABLE_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,
+            final Future<Object> canCommitFuture = Patterns.ask(shard,
                     new CanCommitTransaction(transactionID2).toSerializable(), timeout);
 
             // Send the AbortTransaction message for the first Tx. This should trigger the 2nd
@@ -1191,7 +2187,7 @@ public class ShardTest extends AbstractShardTest {
 
             Await.ready(canCommitFuture, duration);
 
-            InOrder inOrder = inOrder(cohort1, cohort2);
+            final InOrder inOrder = inOrder(cohort1, cohort2);
             inOrder.verify(cohort1).canCommit();
             inOrder.verify(cohort2).canCommit();
 
@@ -1212,82 +2208,67 @@ public class ShardTest extends AbstractShardTest {
     @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;
-            }
-
-            @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(final ShardIdentifier name, final Map<String, String> peerAddresses,
+                                    final DatastoreContext datastoreContext, final SchemaContext schemaContext) {
+                    super(name, peerAddresses, datastoreContext, schemaContext);
+                    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;
-                        }
+                    if (message instanceof SaveSnapshotSuccess || message.equals("commit_snapshot")) {
+                        latch.get().countDown();
+                    }
+                }
 
-                        @Override
-                        protected void commitSnapshot(final long sequenceNumber) {
-                            super.commitSnapshot(sequenceNumber);
-                            latch.get().countDown();
-                        }
-                    };
+                @Override
+                public RaftActorContext getRaftActorContext() {
+                    return super.getRaftActorContext();
+                }
+            }
+
+            final Creator<Shard> creator = new Creator<Shard>() {
+                @Override
+                public Shard create() throws Exception {
+                    return new TestShard(shardID, Collections.<String,String>emptyMap(),
+                            newDatastoreContext(), SCHEMA_CONTEXT);
                 }
             };
 
-            TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
                     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.builder().build());
 
-            CaptureSnapshot capture = new CaptureSnapshot(-1, -1, -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);
 
             assertEquals("Snapshot saved", true, latch.get().await(5, TimeUnit.SECONDS));
 
@@ -1299,7 +2280,7 @@ public class ShardTest extends AbstractShardTest {
             latch.set(new CountDownLatch(1));
             savedSnapshot.set(null);
 
-            shard.tell(capture, getRef());
+            raftActorContext.getSnapshotManager().capture(mock(ReplicatedLogEntry.class), -1);
 
             assertEquals("Snapshot saved", true, latch.get().await(5, TimeUnit.SECONDS));
 
@@ -1311,9 +2292,9 @@ public class ShardTest extends AbstractShardTest {
             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);
 
         }};
@@ -1322,29 +2303,29 @@ public class ShardTest extends AbstractShardTest {
     /**
      * 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());
+    public void testInMemoryDataTreeRestore() throws ReadFailedException, DataValidationFailedException {
+        final DataTree store = InMemoryDataTreeFactory.getInstance().create();
+        store.setSchemaContext(SCHEMA_CONTEXT);
 
-        store.onGlobalContextUpdated(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.builder().build());
 
-        DOMStoreWriteTransaction writeTransaction = store.newWriteOnlyTransaction();
+        final DataTreeModification writeTransaction = store.takeSnapshot().newModification();
 
         writeTransaction.delete(YangInstanceIdentifier.builder().build());
         writeTransaction.write(YangInstanceIdentifier.builder().build(), expected);
 
-        commitTransaction(writeTransaction);
+        commitTransaction(store, writeTransaction);
 
-        NormalizedNode<?, ?> actual = readStore(store);
+        final NormalizedNode<?, ?> actual = readStore(store, YangInstanceIdentifier.builder().build());
 
         assertEquals(expected, actual);
     }
@@ -1355,31 +2336,32 @@ public class ShardTest extends AbstractShardTest {
         final DatastoreContext persistentContext = DatastoreContext.newBuilder().
                 shardJournalRecoveryLogBatchSize(3).shardSnapshotBatchCount(5000).persistent(true).build();
 
-        final Props persistentProps = Shard.props(shardID, Collections.<ShardIdentifier, String>emptyMap(),
+        final Props persistentProps = Shard.props(shardID, Collections.<String, String>emptyMap(),
                 persistentContext, SCHEMA_CONTEXT);
 
         final DatastoreContext nonPersistentContext = DatastoreContext.newBuilder().
                 shardJournalRecoveryLogBatchSize(3).shardSnapshotBatchCount(5000).persistent(false).build();
 
-        final Props nonPersistentProps = Shard.props(shardID, Collections.<ShardIdentifier, String>emptyMap(),
+        final Props nonPersistentProps = Shard.props(shardID, Collections.<String, String>emptyMap(),
                 nonPersistentContext, SCHEMA_CONTEXT);
 
         new ShardTestKit(getSystem()) {{
-            TestActorRef<Shard> shard1 = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard1 = TestActorRef.create(getSystem(),
                     persistentProps, "testPersistence1");
 
-            assertTrue("Recovery Applicable", shard1.underlyingActor().getDataPersistenceProvider().isRecoveryApplicable());
+            assertTrue("Recovery Applicable", shard1.underlyingActor().persistence().isRecoveryApplicable());
 
             shard1.tell(PoisonPill.getInstance(), ActorRef.noSender());
 
-            TestActorRef<Shard> shard2 = TestActorRef.create(getSystem(),
+            final TestActorRef<Shard> shard2 = TestActorRef.create(getSystem(),
                     nonPersistentProps, "testPersistence2");
 
-            assertFalse("Recovery Not Applicable", shard2.underlyingActor().getDataPersistenceProvider().isRecoveryApplicable());
+            assertFalse("Recovery Not Applicable", shard2.underlyingActor().persistence().isRecoveryApplicable());
 
             shard2.tell(PoisonPill.getInstance(), ActorRef.noSender());
 
         }};
+
     }
 
     @Test
@@ -1387,22 +2369,22 @@ public class ShardTest extends AbstractShardTest {
         new ShardTestKit(getSystem()) {{
             dataStoreContextBuilder.persistent(true);
 
-            TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(), "testOnDatastoreContext");
+            final TestActorRef<Shard> shard = TestActorRef.create(getSystem(), newShardProps(), "testOnDatastoreContext");
 
             assertEquals("isRecoveryApplicable", true,
-                    shard.underlyingActor().getDataPersistenceProvider().isRecoveryApplicable());
+                    shard.underlyingActor().persistence().isRecoveryApplicable());
 
             waitUntilLeader(shard);
 
             shard.tell(dataStoreContextBuilder.persistent(false).build(), ActorRef.noSender());
 
             assertEquals("isRecoveryApplicable", false,
-                    shard.underlyingActor().getDataPersistenceProvider().isRecoveryApplicable());
+                    shard.underlyingActor().persistence().isRecoveryApplicable());
 
             shard.tell(dataStoreContextBuilder.persistent(true).build(), ActorRef.noSender());
 
             assertEquals("isRecoveryApplicable", true,
-                    shard.underlyingActor().getDataPersistenceProvider().isRecoveryApplicable());
+                    shard.underlyingActor().persistence().isRecoveryApplicable());
 
             shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
         }};
@@ -1418,19 +2400,32 @@ public class ShardTest extends AbstractShardTest {
 
                 waitUntilLeader(shard);
 
-                TestActorRef<MessageCollectorActor> listener =
+                final TestActorRef<MessageCollectorActor> listener =
                         TestActorRef.create(getSystem(), Props.create(MessageCollectorActor.class));
 
                 shard.tell(new RegisterRoleChangeListener(), listener);
 
-                // TODO: MessageCollectorActor exists as a test util in both the akka-raft and distributed-datastore
-                // projects. Need to move it to commons as a regular utility and then we can get rid of this arbitrary
-                // sleep.
-                Uninterruptibles.sleepUninterruptibly(100, TimeUnit.MILLISECONDS);
+                MessageCollectorActor.expectFirstMatching(listener, RegisterRoleChangeListenerReply.class);
+
+                ShardLeaderStateChanged leaderStateChanged = MessageCollectorActor.expectFirstMatching(listener,
+                        ShardLeaderStateChanged.class);
+                assertEquals("getLocalShardDataTree present", true,
+                        leaderStateChanged.getLocalShardDataTree().isPresent());
+                assertSame("getLocalShardDataTree", shard.underlyingActor().getDataStore().getDataTree(),
+                        leaderStateChanged.getLocalShardDataTree().get());
+
+                MessageCollectorActor.clearMessages(listener);
 
-                List<Object> allMatching = MessageCollectorActor.getAllMatching(listener, RegisterRoleChangeListenerReply.class);
+                // Force a leader change
 
-                assertEquals(1, allMatching.size());
+                shard.tell(new RequestVote(10000, "member2", 50, 50), getRef());
+
+                leaderStateChanged = MessageCollectorActor.expectFirstMatching(listener,
+                        ShardLeaderStateChanged.class);
+                assertEquals("getLocalShardDataTree present", false,
+                        leaderStateChanged.getLocalShardDataTree().isPresent());
+
+                shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
             }
         };
     }
@@ -1452,15 +2447,9 @@ public class ShardTest extends AbstractShardTest {
         shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
     }
 
-    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) {
-        }
+    private static void commitTransaction(final DataTree store, final DataTreeModification modification) throws DataValidationFailedException {
+        modification.ready();
+        store.validate(modification);
+        store.commit(store.prepare(modification));
     }
 }