Bug 2486: Get testAbortBeforeFinishCommit working again
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / main / java / org / opendaylight / controller / cluster / datastore / Shard.java
index 770cdec39ceb430b8b1be1cbd1b4ef63ba0abbd7..7ef6e040a9f3f0d94bf2fdc47790377d505184b3 100644 (file)
@@ -27,9 +27,18 @@ import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.protobuf.ByteString;
 import com.google.protobuf.InvalidProtocolBufferException;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import javax.annotation.Nonnull;
+import org.opendaylight.controller.cluster.DataPersistenceProvider;
 import org.opendaylight.controller.cluster.common.actor.CommonConfig;
 import org.opendaylight.controller.cluster.common.actor.MeteringBehavior;
 import org.opendaylight.controller.cluster.datastore.ShardCommitCoordinator.CohortEntry;
+import org.opendaylight.controller.cluster.datastore.compat.BackwardsCompatibleThreePhaseCommitCohort;
 import org.opendaylight.controller.cluster.datastore.exceptions.NoShardLeaderException;
 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
 import org.opendaylight.controller.cluster.datastore.identifiers.ShardTransactionIdentifier;
@@ -56,9 +65,11 @@ import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContex
 import org.opendaylight.controller.cluster.datastore.modification.Modification;
 import org.opendaylight.controller.cluster.datastore.modification.MutableCompositeModification;
 import org.opendaylight.controller.cluster.datastore.node.NormalizedNodeToNodeCodec;
+import org.opendaylight.controller.cluster.notifications.RoleChangeNotifier;
 import org.opendaylight.controller.cluster.raft.RaftActor;
 import org.opendaylight.controller.cluster.raft.ReplicatedLogEntry;
 import org.opendaylight.controller.cluster.raft.base.messages.CaptureSnapshotReply;
+import org.opendaylight.controller.cluster.raft.protobuff.client.messages.CompositeModificationByteStringPayload;
 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.CompositeModificationPayload;
 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeListener;
@@ -76,14 +87,6 @@ import org.opendaylight.yangtools.yang.model.api.SchemaContext;
 import scala.concurrent.duration.Duration;
 import scala.concurrent.duration.FiniteDuration;
 
-import javax.annotation.Nonnull;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.TimeUnit;
-
 /**
  * A Shard represents a portion of the logical data tree <br/>
  * <p>
@@ -104,10 +107,6 @@ public class Shard extends RaftActor {
     private final LoggingAdapter LOG =
         Logging.getLogger(getContext().system(), this);
 
-    // By default persistent will be true and can be turned off using the system
-    // property shard.persistent
-    private final boolean persistent;
-
     /// The name of this shard
     private final ShardIdentifier name;
 
@@ -120,6 +119,8 @@ public class Shard extends RaftActor {
 
     private final DatastoreContext datastoreContext;
 
+    private final DataPersistenceProvider dataPersistenceProvider;
+
     private SchemaContext schemaContext;
 
     private ActorRef createSnapshotTransaction;
@@ -132,6 +133,8 @@ public class Shard extends RaftActor {
 
     private Cancellable txCommitTimeoutCheckSchedule;
 
+    private final Optional<ActorRef> roleChangeNotifier;
+
     /**
      * Coordinates persistence recovery on startup.
      */
@@ -140,20 +143,17 @@ public class Shard extends RaftActor {
 
     private final Map<String, DOMStoreTransactionChain> transactionChains = new HashMap<>();
 
-    protected Shard(ShardIdentifier name, Map<ShardIdentifier, String> peerAddresses,
-            DatastoreContext datastoreContext, SchemaContext schemaContext) {
+    protected Shard(final ShardIdentifier name, final Map<ShardIdentifier, String> peerAddresses,
+            final DatastoreContext datastoreContext, final SchemaContext schemaContext) {
         super(name.toString(), mapPeerAddresses(peerAddresses),
                 Optional.of(datastoreContext.getShardRaftConfig()));
 
         this.name = name;
         this.datastoreContext = datastoreContext;
         this.schemaContext = schemaContext;
+        this.dataPersistenceProvider = (datastoreContext.isPersistent()) ? new PersistentDataProvider() : new NonPersistentRaftDataProvider();
 
-        String setting = System.getProperty("shard.persistent");
-
-        this.persistent = !"false".equals(setting);
-
-        LOG.info("Shard created : {} persistent : {}", name, persistent);
+        LOG.info("Shard created : {} persistent : {}", name, datastoreContext.isPersistent());
 
         store = InMemoryDOMDataStoreFactory.create(name.toString(), null,
                 datastoreContext.getDataStoreProperties());
@@ -164,7 +164,6 @@ public class Shard extends RaftActor {
 
         shardMBean = ShardMBeanFactory.getShardStatsMBean(name.toString(),
                 datastoreContext.getDataStoreMXBeanType());
-        shardMBean.setDataStoreExecutor(store.getDomStoreExecutor());
         shardMBean.setNotificationManager(store.getDataChangeListenerNotificationManager());
 
         if (isMetricsCaptureEnabled()) {
@@ -176,10 +175,13 @@ public class Shard extends RaftActor {
 
         transactionCommitTimeout = TimeUnit.MILLISECONDS.convert(
                 datastoreContext.getShardTransactionCommitTimeoutInSeconds(), TimeUnit.SECONDS);
+
+        // create a notifier actor for each cluster member
+        roleChangeNotifier = createRoleChangeNotifier(name.toString());
     }
 
     private static Map<String, String> mapPeerAddresses(
-        Map<ShardIdentifier, String> peerAddresses) {
+        final Map<ShardIdentifier, String> peerAddresses) {
         Map<String, String> map = new HashMap<>();
 
         for (Map.Entry<ShardIdentifier, String> entry : peerAddresses
@@ -192,7 +194,7 @@ public class Shard extends RaftActor {
 
     public static Props props(final ShardIdentifier name,
         final Map<ShardIdentifier, String> peerAddresses,
-        DatastoreContext datastoreContext, SchemaContext schemaContext) {
+        final DatastoreContext datastoreContext, final SchemaContext schemaContext) {
         Preconditions.checkNotNull(name, "name should not be null");
         Preconditions.checkNotNull(peerAddresses, "peerAddresses should not be null");
         Preconditions.checkNotNull(datastoreContext, "dataStoreContext should not be null");
@@ -201,6 +203,12 @@ public class Shard extends RaftActor {
         return Props.create(new ShardCreator(name, peerAddresses, datastoreContext, schemaContext));
     }
 
+    private Optional<ActorRef> createRoleChangeNotifier(String shardId) {
+        ActorRef shardRoleChangeNotifier = this.getContext().actorOf(
+            RoleChangeNotifier.getProps(shardId), shardId + "-notifier");
+        return Optional.<ActorRef>of(shardRoleChangeNotifier);
+    }
+
     @Override
     public void postStop() {
         super.postStop();
@@ -211,7 +219,7 @@ public class Shard extends RaftActor {
     }
 
     @Override
-    public void onReceiveRecover(Object message) {
+    public void onReceiveRecover(final Object message) throws Exception {
         if(LOG.isDebugEnabled()) {
             LOG.debug("onReceiveRecover: Received message {} from {}",
                 message.getClass().toString(),
@@ -230,7 +238,7 @@ public class Shard extends RaftActor {
     }
 
     @Override
-    public void onReceiveCommand(Object message) {
+    public void onReceiveCommand(final Object message) throws Exception {
         if(LOG.isDebugEnabled()) {
             LOG.debug("onReceiveCommand: Received message {} from {}", message, getSender());
         }
@@ -264,6 +272,11 @@ public class Shard extends RaftActor {
         }
     }
 
+    @Override
+    protected Optional<ActorRef> getRoleChangeNotifier() {
+        return roleChangeNotifier;
+    }
+
     private void handleTransactionCommitTimeoutCheck() {
         CohortEntry cohortEntry = commitCoordinator.getCurrentCohortEntry();
         if(cohortEntry != null) {
@@ -277,7 +290,7 @@ public class Shard extends RaftActor {
         }
     }
 
-    private void handleCommitTransaction(CommitTransaction commit) {
+    private void handleCommitTransaction(final CommitTransaction commit) {
         final String transactionID = commit.getTransactionID();
 
         LOG.debug("Committing transaction {}", transactionID);
@@ -308,11 +321,13 @@ public class Shard extends RaftActor {
             // currently uses a same thread executor anyway.
             cohortEntry.getCohort().preCommit().get();
 
-            if(persistent) {
-                Shard.this.persistData(getSender(), transactionID,
-                        new CompositeModificationPayload(cohortEntry.getModification().toSerializable()));
+            // If we do not have any followers and we are not using persistence we can
+            // apply modification to the state immediately
+            if(!hasFollowers() && !persistence().isRecoveryApplicable()){
+                applyModificationToState(getSender(), transactionID, cohortEntry.getModification());
             } else {
-                Shard.this.finishCommit(getSender(), transactionID);
+                Shard.this.persistData(getSender(), transactionID,
+                        new CompositeModificationByteStringPayload(cohortEntry.getModification().toSerializable()));
             }
         } catch (InterruptedException | ExecutionException e) {
             LOG.error(e, "An exception occurred while preCommitting transaction {}",
@@ -376,13 +391,14 @@ public class Shard extends RaftActor {
         commitCoordinator.currentTransactionComplete(transactionID, true);
     }
 
-    private void handleCanCommitTransaction(CanCommitTransaction canCommit) {
+    private void handleCanCommitTransaction(final CanCommitTransaction canCommit) {
         LOG.debug("Can committing transaction {}", canCommit.getTransactionID());
         commitCoordinator.handleCanCommit(canCommit, getSender(), self());
     }
 
     private void handleForwardedReadyTransaction(ForwardedReadyTransaction ready) {
-        LOG.debug("Readying transaction {}", ready.getTransactionID());
+        LOG.debug("Readying transaction {}, client version {}", ready.getTransactionID(),
+                ready.getTxnClientVersion());
 
         // This message is forwarded by the ShardTransaction on ready. We cache the cohort in the
         // commitCoordinator in preparation for the subsequent three phase commit initiated by
@@ -390,19 +406,29 @@ public class Shard extends RaftActor {
         commitCoordinator.transactionReady(ready.getTransactionID(), ready.getCohort(),
                 ready.getModification());
 
-        // Return our actor path as we'll handle the three phase commit.
-        ReadyTransactionReply readyTransactionReply =
-            new ReadyTransactionReply(Serialization.serializedActorPath(self()));
-        getSender().tell(
-            ready.isReturnSerialized() ? readyTransactionReply.toSerializable() : readyTransactionReply,
-            getSelf());
+        // Return our actor path as we'll handle the three phase commit, except if the Tx client
+        // version < 1 (Helium-1 version). This means the Tx was initiated by a base Helium version
+        // node. In that case, the subsequent 3-phase commit messages won't contain the
+        // transactionId so to maintain backwards compatibility, we create a separate cohort actor
+        // to provide the compatible behavior.
+        ActorRef replyActorPath = self();
+        if(ready.getTxnClientVersion() < CreateTransaction.HELIUM_1_VERSION) {
+            LOG.debug("Creating BackwardsCompatibleThreePhaseCommitCohort");
+            replyActorPath = getContext().actorOf(BackwardsCompatibleThreePhaseCommitCohort.props(
+                    ready.getTransactionID()));
+        }
+
+        ReadyTransactionReply readyTransactionReply = new ReadyTransactionReply(
+                Serialization.serializedActorPath(replyActorPath));
+        getSender().tell(ready.isReturnSerialized() ? readyTransactionReply.toSerializable() :
+                readyTransactionReply, getSelf());
     }
 
-    private void handleAbortTransaction(AbortTransaction abort) {
+    private void handleAbortTransaction(final AbortTransaction abort) {
         doAbortTransaction(abort.getTransactionID(), getSender());
     }
 
-    private void doAbortTransaction(String transactionID, final ActorRef sender) {
+    void doAbortTransaction(final String transactionID, final ActorRef sender) {
         final CohortEntry cohortEntry = commitCoordinator.getCohortEntryIfCurrent(transactionID);
         if(cohortEntry != null) {
             LOG.debug("Aborting transaction {}", transactionID);
@@ -417,7 +443,7 @@ public class Shard extends RaftActor {
 
             Futures.addCallback(future, new FutureCallback<Void>() {
                 @Override
-                public void onSuccess(Void v) {
+                public void onSuccess(final Void v) {
                     shardMBean.incrementAbortTransactionsCount();
 
                     if(sender != null) {
@@ -426,7 +452,7 @@ public class Shard extends RaftActor {
                 }
 
                 @Override
-                public void onFailure(Throwable t) {
+                public void onFailure(final Throwable t) {
                     LOG.error(t, "An exception happened during abort");
 
                     if(sender != null) {
@@ -437,7 +463,7 @@ public class Shard extends RaftActor {
         }
     }
 
-    private void handleCreateTransaction(Object message) {
+    private void handleCreateTransaction(final Object message) {
         if (isLeader()) {
             createTransaction(CreateTransaction.fromSerializable(message));
         } else if (getLeader() != null) {
@@ -450,7 +476,7 @@ public class Shard extends RaftActor {
         }
     }
 
-    private void handleReadDataReply(Object message) {
+    private void handleReadDataReply(final Object message) {
         // This must be for install snapshot. Don't want to open this up and trigger
         // deSerialization
 
@@ -464,7 +490,7 @@ public class Shard extends RaftActor {
         getSender().tell(PoisonPill.getInstance(), self());
     }
 
-    private void closeTransactionChain(CloseTransactionChain closeTransactionChain) {
+    private void closeTransactionChain(final CloseTransactionChain closeTransactionChain) {
         DOMStoreTransactionChain chain =
             transactionChains.remove(closeTransactionChain.getTransactionChainId());
 
@@ -473,10 +499,8 @@ public class Shard extends RaftActor {
         }
     }
 
-    private ActorRef createTypedTransactionActor(
-        int transactionType,
-        ShardTransactionIdentifier transactionId,
-        String transactionChainId ) {
+    private ActorRef createTypedTransactionActor(int transactionType,
+            ShardTransactionIdentifier transactionId, String transactionChainId, int clientVersion ) {
 
         DOMStoreTransactionFactory factory = store;
 
@@ -489,8 +513,8 @@ public class Shard extends RaftActor {
             }
         }
 
-        if(this.schemaContext == null){
-            throw new NullPointerException("schemaContext should not be null");
+        if(this.schemaContext == null) {
+            throw new IllegalStateException("SchemaContext is not set");
         }
 
         if (transactionType == TransactionProxy.TransactionType.READ_ONLY.ordinal()) {
@@ -500,7 +524,8 @@ public class Shard extends RaftActor {
             return getContext().actorOf(
                 ShardTransaction.props(factory.newReadOnlyTransaction(), getSelf(),
                         schemaContext,datastoreContext, shardMBean,
-                        transactionId.getRemoteTransactionId()), transactionId.toString());
+                        transactionId.getRemoteTransactionId(), clientVersion),
+                        transactionId.toString());
 
         } else if (transactionType == TransactionProxy.TransactionType.READ_WRITE.ordinal()) {
 
@@ -509,7 +534,8 @@ public class Shard extends RaftActor {
             return getContext().actorOf(
                 ShardTransaction.props(factory.newReadWriteTransaction(), getSelf(),
                         schemaContext, datastoreContext, shardMBean,
-                        transactionId.getRemoteTransactionId()), transactionId.toString());
+                        transactionId.getRemoteTransactionId(), clientVersion),
+                        transactionId.toString());
 
 
         } else if (transactionType == TransactionProxy.TransactionType.WRITE_ONLY.ordinal()) {
@@ -519,7 +545,8 @@ public class Shard extends RaftActor {
             return getContext().actorOf(
                 ShardTransaction.props(factory.newWriteOnlyTransaction(), getSelf(),
                         schemaContext, datastoreContext, shardMBean,
-                        transactionId.getRemoteTransactionId()), transactionId.toString());
+                        transactionId.getRemoteTransactionId(), clientVersion),
+                        transactionId.toString());
         } else {
             throw new IllegalArgumentException(
                 "Shard="+name + ":CreateTransaction message has unidentified transaction type="
@@ -528,39 +555,44 @@ public class Shard extends RaftActor {
     }
 
     private void createTransaction(CreateTransaction createTransaction) {
-        createTransaction(createTransaction.getTransactionType(),
-            createTransaction.getTransactionId(), createTransaction.getTransactionChainId());
+        try {
+            ActorRef transactionActor = createTransaction(createTransaction.getTransactionType(),
+                createTransaction.getTransactionId(), createTransaction.getTransactionChainId(),
+                createTransaction.getVersion());
+
+            getSender().tell(new CreateTransactionReply(Serialization.serializedActorPath(transactionActor),
+                    createTransaction.getTransactionId()).toSerializable(), getSelf());
+        } catch (Exception e) {
+            getSender().tell(new akka.actor.Status.Failure(e), getSelf());
+        }
     }
 
-    private ActorRef createTransaction(int transactionType, String remoteTransactionId, String transactionChainId) {
+    private ActorRef createTransaction(int transactionType, String remoteTransactionId,
+            String transactionChainId, int clientVersion) {
 
         ShardTransactionIdentifier transactionId =
             ShardTransactionIdentifier.builder()
                 .remoteTransactionId(remoteTransactionId)
                 .build();
+
         if(LOG.isDebugEnabled()) {
             LOG.debug("Creating transaction : {} ", transactionId);
         }
-        ActorRef transactionActor =
-            createTypedTransactionActor(transactionType, transactionId, transactionChainId);
 
-        getSender()
-            .tell(new CreateTransactionReply(
-                    Serialization.serializedActorPath(transactionActor),
-                    remoteTransactionId).toSerializable(),
-                getSelf());
+        ActorRef transactionActor = createTypedTransactionActor(transactionType, transactionId,
+                transactionChainId, clientVersion);
 
         return transactionActor;
     }
 
-    private void syncCommitTransaction(DOMStoreWriteTransaction transaction)
+    private void syncCommitTransaction(final DOMStoreWriteTransaction transaction)
         throws ExecutionException, InterruptedException {
         DOMStoreThreePhaseCommitCohort commitCohort = transaction.ready();
         commitCohort.preCommit().get();
         commitCohort.commit().get();
     }
 
-    private void commitWithNewTransaction(Modification modification) {
+    private void commitWithNewTransaction(final Modification modification) {
         DOMStoreWriteTransaction tx = store.newWriteOnlyTransaction();
         modification.apply(tx);
         try {
@@ -573,18 +605,18 @@ public class Shard extends RaftActor {
         }
     }
 
-    private void updateSchemaContext(UpdateSchemaContext message) {
+    private void updateSchemaContext(final UpdateSchemaContext message) {
         this.schemaContext = message.getSchemaContext();
         updateSchemaContext(message.getSchemaContext());
         store.onGlobalContextUpdated(message.getSchemaContext());
     }
 
     @VisibleForTesting
-    void updateSchemaContext(SchemaContext schemaContext) {
+    void updateSchemaContext(final SchemaContext schemaContext) {
         store.onGlobalContextUpdated(schemaContext);
     }
 
-    private void registerChangeListener(RegisterChangeListener registerChangeListener) {
+    private void registerChangeListener(final RegisterChangeListener registerChangeListener) {
 
         LOG.debug("registerDataChangeListener for {}", registerChangeListener.getPath());
 
@@ -607,12 +639,12 @@ public class Shard extends RaftActor {
         LOG.debug("registerDataChangeListener sending reply, listenerRegistrationPath = {} ",
                     listenerRegistration.path());
 
-        getSender().tell(new RegisterChangeListenerReply(listenerRegistration.path()),getSelf());
+        getSender().tell(new RegisterChangeListenerReply(listenerRegistration.path()), getSelf());
     }
 
     private ListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier,
                                                NormalizedNode<?, ?>>> doChangeListenerRegistration(
-            RegisterChangeListener registerChangeListener) {
+            final RegisterChangeListener registerChangeListener) {
 
         ActorSelection dataChangeListenerPath = getContext().system().actorSelection(
                 registerChangeListener.getDataChangeListenerPath());
@@ -642,7 +674,7 @@ public class Shard extends RaftActor {
 
     @Override
     protected
-    void startLogRecoveryBatch(int maxBatchSize) {
+    void startLogRecoveryBatch(final int maxBatchSize) {
         currentLogRecoveryBatch = Lists.newArrayListWithCapacity(maxBatchSize);
 
         if(LOG.isDebugEnabled()) {
@@ -651,16 +683,18 @@ public class Shard extends RaftActor {
     }
 
     @Override
-    protected void appendRecoveredLogEntry(Payload data) {
+    protected void appendRecoveredLogEntry(final Payload data) {
         if (data instanceof CompositeModificationPayload) {
             currentLogRecoveryBatch.add(((CompositeModificationPayload) data).getModification());
+        } else if (data instanceof CompositeModificationByteStringPayload) {
+            currentLogRecoveryBatch.add(((CompositeModificationByteStringPayload) data).getModification());
         } else {
             LOG.error("Unknown state received {} during recovery", data);
         }
     }
 
     @Override
-    protected void applyRecoverySnapshot(ByteString snapshot) {
+    protected void applyRecoverySnapshot(final ByteString snapshot) {
         if(recoveryCoordinator == null) {
             recoveryCoordinator = new ShardRecoveryCoordinator(persistenceId(), schemaContext);
         }
@@ -725,24 +759,17 @@ public class Shard extends RaftActor {
     }
 
     @Override
-    protected void applyState(ActorRef clientActor, String identifier, Object data) {
+    protected void applyState(final ActorRef clientActor, final String identifier, final Object data) {
 
         if (data instanceof CompositeModificationPayload) {
             Object modification = ((CompositeModificationPayload) data).getModification();
 
-            if(modification == null) {
-                LOG.error(
-                     "modification is null - this is very unexpected, clientActor = {}, identifier = {}",
-                     identifier, clientActor != null ? clientActor.path().toString() : null);
-            } else if(clientActor == null) {
-                // There's no clientActor to which to send a commit reply so we must be applying
-                // replicated state from the leader.
-                commitWithNewTransaction(MutableCompositeModification.fromSerializable(
-                        modification, schemaContext));
-            } else {
-                // This must be the OK to commit after replication consensus.
-                finishCommit(clientActor, identifier);
-            }
+            applyModificationToState(clientActor, identifier, modification);
+        } else if(data instanceof CompositeModificationByteStringPayload ){
+            Object modification = ((CompositeModificationByteStringPayload) data).getModification();
+
+            applyModificationToState(clientActor, identifier, modification);
+
         } else {
             LOG.error("Unknown state received {} Class loader = {} CompositeNodeMod.ClassLoader = {}",
                     data, data.getClass().getClassLoader(),
@@ -753,6 +780,22 @@ public class Shard extends RaftActor {
 
     }
 
+    private void applyModificationToState(ActorRef clientActor, String identifier, Object modification) {
+        if(modification == null) {
+            LOG.error(
+                    "modification is null - this is very unexpected, clientActor = {}, identifier = {}",
+                    identifier, clientActor != null ? clientActor.path().toString() : null);
+        } else if(clientActor == null) {
+            // There's no clientActor to which to send a commit reply so we must be applying
+            // replicated state from the leader.
+            commitWithNewTransaction(MutableCompositeModification.fromSerializable(
+                    modification, schemaContext));
+        } else {
+            // This must be the OK to commit after replication consensus.
+            finishCommit(clientActor, identifier);
+        }
+    }
+
     private void updateJournalStats() {
         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 
@@ -763,6 +806,7 @@ public class Shard extends RaftActor {
 
         shardMBean.setCommitIndex(getCommitIndex());
         shardMBean.setLastApplied(getLastApplied());
+        shardMBean.setInMemoryJournalDataSize(getRaftActorContext().getReplicatedLog().dataSize());
     }
 
     @Override
@@ -773,7 +817,8 @@ public class Shard extends RaftActor {
             // so that this actor does not get block building the snapshot
             createSnapshotTransaction = createTransaction(
                 TransactionProxy.TransactionType.READ_ONLY.ordinal(),
-                "createSnapshot" + ++createSnapshotTransactionCounter, "");
+                "createSnapshot" + ++createSnapshotTransactionCounter, "",
+                CreateTransaction.CURRENT_VERSION);
 
             createSnapshotTransaction.tell(
                 new ReadData(YangInstanceIdentifier.builder().build()).toSerializable(), self());
@@ -783,7 +828,7 @@ public class Shard extends RaftActor {
 
     @VisibleForTesting
     @Override
-    protected void applySnapshot(ByteString snapshot) {
+    protected void applySnapshot(final ByteString snapshot) {
         // Since this will be done only on Recovery or when this actor is a Follower
         // we can safely commit everything in here. We not need to worry about event notifications
         // as they would have already been disabled on the follower
@@ -843,7 +888,12 @@ public class Shard extends RaftActor {
         }
     }
 
-    @Override protected void onLeaderChanged(String oldLeader, String newLeader) {
+    @Override
+    protected DataPersistenceProvider persistence() {
+        return dataPersistenceProvider;
+    }
+
+    @Override protected void onLeaderChanged(final String oldLeader, final String newLeader) {
         shardMBean.setLeader(newLeader);
     }
 
@@ -851,6 +901,11 @@ public class Shard extends RaftActor {
         return this.name.toString();
     }
 
+    @VisibleForTesting
+    DataPersistenceProvider getDataPersistenceProvider() {
+        return dataPersistenceProvider;
+    }
+
     private static class ShardCreator implements Creator<Shard> {
 
         private static final long serialVersionUID = 1L;
@@ -860,8 +915,8 @@ public class Shard extends RaftActor {
         final DatastoreContext datastoreContext;
         final SchemaContext schemaContext;
 
-        ShardCreator(ShardIdentifier name, Map<ShardIdentifier, String> peerAddresses,
-                DatastoreContext datastoreContext, SchemaContext schemaContext) {
+        ShardCreator(final ShardIdentifier name, final Map<ShardIdentifier, String> peerAddresses,
+                final DatastoreContext datastoreContext, final SchemaContext schemaContext) {
             this.name = name;
             this.peerAddresses = peerAddresses;
             this.datastoreContext = datastoreContext;
@@ -894,11 +949,11 @@ public class Shard extends RaftActor {
         private volatile ListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier,
                                                              NormalizedNode<?, ?>>> delegate;
 
-        DelayedListenerRegistration(RegisterChangeListener registerChangeListener) {
+        DelayedListenerRegistration(final RegisterChangeListener registerChangeListener) {
             this.registerChangeListener = registerChangeListener;
         }
 
-        void setDelegate( ListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier,
+        void setDelegate( final ListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier,
                                             NormalizedNode<?, ?>>> registration) {
             this.delegate = registration;
         }