Bug 1831 Batch messages on journal recovery
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / main / java / org / opendaylight / controller / cluster / datastore / Shard.java
index 21fea96320f30754baa2c300877c768c895b4d02..ddb5989f096145cddd3b716afa8dfc1dce3311e3 100644 (file)
@@ -10,50 +10,69 @@ package org.opendaylight.controller.cluster.datastore;
 
 import akka.actor.ActorRef;
 import akka.actor.ActorSelection;
+import akka.actor.PoisonPill;
 import akka.actor.Props;
 import akka.event.Logging;
 import akka.event.LoggingAdapter;
 import akka.japi.Creator;
+import akka.persistence.RecoveryFailure;
 import akka.serialization.Serialization;
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Optional;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Lists;
+import com.google.common.util.concurrent.CheckedFuture;
+import com.google.common.util.concurrent.FutureCallback;
+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 org.opendaylight.controller.cluster.common.actor.CommonConfig;
+import org.opendaylight.controller.cluster.common.actor.MeteringBehavior;
+import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
+import org.opendaylight.controller.cluster.datastore.identifiers.ShardTransactionIdentifier;
 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardMBeanFactory;
 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardStats;
+import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
 import org.opendaylight.controller.cluster.datastore.messages.CommitTransactionReply;
 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
-import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionChain;
-import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionChainReply;
 import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
 import org.opendaylight.controller.cluster.datastore.messages.EnableNotification;
 import org.opendaylight.controller.cluster.datastore.messages.ForwardedCommitTransaction;
 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.RegisterChangeListener;
 import org.opendaylight.controller.cluster.datastore.messages.RegisterChangeListenerReply;
 import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContext;
 import org.opendaylight.controller.cluster.datastore.modification.Modification;
 import org.opendaylight.controller.cluster.datastore.modification.MutableCompositeModification;
-import org.opendaylight.controller.cluster.raft.ConfigParams;
-import org.opendaylight.controller.cluster.raft.DefaultConfigParamsImpl;
+import org.opendaylight.controller.cluster.datastore.node.NormalizedNodeToNodeCodec;
 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.CompositeModificationPayload;
+import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeListener;
+import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
 import org.opendaylight.controller.md.sal.dom.store.impl.InMemoryDOMDataStore;
 import org.opendaylight.controller.md.sal.dom.store.impl.InMemoryDOMDataStoreFactory;
-import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadWriteTransaction;
+import org.opendaylight.controller.protobuff.messages.common.NormalizedNodeMessages;
+import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadTransaction;
 import org.opendaylight.controller.sal.core.spi.data.DOMStoreThreePhaseCommitCohort;
 import org.opendaylight.controller.sal.core.spi.data.DOMStoreTransactionChain;
+import org.opendaylight.controller.sal.core.spi.data.DOMStoreTransactionFactory;
+import org.opendaylight.controller.sal.core.spi.data.DOMStoreWriteTransaction;
+import org.opendaylight.yangtools.concepts.ListenerRegistration;
 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
-import scala.concurrent.duration.FiniteDuration;
-
 import java.util.ArrayList;
-import java.util.Date;
+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/>
@@ -63,10 +82,9 @@ import java.util.concurrent.TimeUnit;
  */
 public class Shard extends RaftActor {
 
-    private static final ConfigParams configParams = new ShardConfigParams();
-
     public static final String DEFAULT_NAME = "default";
 
+    // The state of this Shard
     private final InMemoryDOMDataStore store;
 
     private final Map<Object, DOMStoreThreePhaseCommitCohort>
@@ -76,58 +94,120 @@ public class Shard extends RaftActor {
         Logging.getLogger(getContext().system(), this);
 
     // By default persistent will be true and can be turned off using the system
-    // property persistent
+    // property shard.persistent
     private final boolean persistent;
 
-    private final String name;
-
-    private volatile SchemaContext schemaContext;
+    /// The name of this shard
+    private final ShardIdentifier name;
 
     private final ShardStats shardMBean;
 
     private final List<ActorSelection> dataChangeListeners = new ArrayList<>();
 
-    private Shard(String name, Map<String, String> peerAddresses) {
-        super(name, peerAddresses, Optional.of(configParams));
+    private final DatastoreContext datastoreContext;
+
+    private SchemaContext schemaContext;
+
+    private ActorRef createSnapshotTransaction;
+
+    /**
+     * Coordinates persistence recovery on startup.
+     */
+    private ShardRecoveryCoordinator recoveryCoordinator;
+    private List<Object> currentLogRecoveryBatch;
+
+    private final Map<String, DOMStoreTransactionChain> transactionChains = new HashMap<>();
+
+    protected Shard(ShardIdentifier name, Map<ShardIdentifier, String> peerAddresses,
+            DatastoreContext datastoreContext, SchemaContext schemaContext) {
+        super(name.toString(), mapPeerAddresses(peerAddresses),
+                Optional.of(datastoreContext.getShardRaftConfig()));
 
         this.name = name;
+        this.datastoreContext = datastoreContext;
+        this.schemaContext = schemaContext;
 
         String setting = System.getProperty("shard.persistent");
 
         this.persistent = !"false".equals(setting);
 
-        LOG.info("Creating shard : {} persistent : {}", name, persistent);
+        LOG.info("Shard created : {} persistent : {}", name, persistent);
 
-        store = InMemoryDOMDataStoreFactory.create(name, null);
+        store = InMemoryDOMDataStoreFactory.create(name.toString(), null,
+                datastoreContext.getDataStoreProperties());
+
+        if(schemaContext != null) {
+            store.onGlobalContextUpdated(schemaContext);
+        }
 
-        shardMBean = ShardMBeanFactory.getShardStatsMBean(name);
+        shardMBean = ShardMBeanFactory.getShardStatsMBean(name.toString(),
+                datastoreContext.getDataStoreMXBeanType());
+        shardMBean.setDataStoreExecutor(store.getDomStoreExecutor());
+        shardMBean.setNotificationManager(store.getDataChangeListenerNotificationManager());
 
+        if (isMetricsCaptureEnabled()) {
+            getContext().become(new MeteringBehavior(this));
+        }
     }
 
-    public static Props props(final String name,
-        final Map<String, String> peerAddresses) {
-        return Props.create(new Creator<Shard>() {
+    private static Map<String, String> mapPeerAddresses(
+        Map<ShardIdentifier, String> peerAddresses) {
+        Map<String, String> map = new HashMap<>();
 
-            @Override
-            public Shard create() throws Exception {
-                return new Shard(name, peerAddresses);
-            }
+        for (Map.Entry<ShardIdentifier, String> entry : peerAddresses
+            .entrySet()) {
+            map.put(entry.getKey().toString(), entry.getValue());
+        }
 
-        });
+        return map;
     }
 
+    public static Props props(final ShardIdentifier name,
+        final Map<ShardIdentifier, String> peerAddresses,
+        DatastoreContext datastoreContext, 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");
+        Preconditions.checkNotNull(schemaContext, "schemaContext should not be null");
+
+        return Props.create(new ShardCreator(name, peerAddresses, datastoreContext, schemaContext));
+    }
+
+    @Override public void onReceiveRecover(Object message) {
+        if(LOG.isDebugEnabled()) {
+            LOG.debug("onReceiveRecover: Received message {} from {}",
+                message.getClass().toString(),
+                getSender());
+        }
+
+        if (message instanceof RecoveryFailure){
+            LOG.error(((RecoveryFailure) message).cause(), "Recovery failed because of this cause");
+        } else {
+            super.onReceiveRecover(message);
+        }
+    }
 
     @Override public void onReceiveCommand(Object message) {
-        LOG.debug("Received message {} from {}", message.getClass().toString(),
-            getSender());
+        if(LOG.isDebugEnabled()) {
+            LOG.debug("onReceiveCommand: Received message {} from {}",
+                message.getClass().toString(),
+                getSender());
+        }
 
-        if (message.getClass()
-            .equals(CreateTransactionChain.SERIALIZABLE_CLASS)) {
-            if (isLeader()) {
-                createTransactionChain();
-            } else if (getLeader() != null) {
-                getLeader().forward(message, getContext());
-            }
+        if(message.getClass().equals(ReadDataReply.SERIALIZABLE_CLASS)) {
+            // This must be for install snapshot. Don't want to open this up and trigger
+            // deSerialization
+            self()
+                .tell(new CaptureSnapshotReply(ReadDataReply.getNormalizedNodeByteString(message)),
+                    self());
+
+            createSnapshotTransaction = null;
+            // Send a PoisonPill instead of sending close transaction because we do not really need
+            // a response
+            getSender().tell(PoisonPill.getInstance(), self());
+
+        } else if (message.getClass().equals(CloseTransactionChain.SERIALIZABLE_CLASS)){
+            closeTransactionChain(CloseTransactionChain.fromSerializable(message));
         } else if (message instanceof RegisterChangeListener) {
             registerChangeListener((RegisterChangeListener) message);
         } else if (message instanceof UpdateSchemaContext) {
@@ -140,110 +220,162 @@ public class Shard extends RaftActor {
                 createTransaction(CreateTransaction.fromSerializable(message));
             } else if (getLeader() != null) {
                 getLeader().forward(message, getContext());
+            } else {
+                getSender().tell(new akka.actor.Status.Failure(new IllegalStateException(
+                    "Could not find leader so transaction cannot be created")), getSelf());
             }
         } else if (message instanceof PeerAddressResolved) {
             PeerAddressResolved resolved = (PeerAddressResolved) message;
-            setPeerAddress(resolved.getPeerId(), resolved.getPeerAddress());
-        } else{
+            setPeerAddress(resolved.getPeerId().toString(),
+                resolved.getPeerAddress());
+        } else {
             super.onReceiveCommand(message);
         }
     }
 
+    private void closeTransactionChain(CloseTransactionChain closeTransactionChain) {
+        DOMStoreTransactionChain chain =
+            transactionChains.remove(closeTransactionChain.getTransactionChainId());
+
+        if(chain != null) {
+            chain.close();
+        }
+    }
+
     private ActorRef createTypedTransactionActor(
-        CreateTransaction createTransaction, String transactionId) {
-        if (createTransaction.getTransactionType()
+        int transactionType,
+        ShardTransactionIdentifier transactionId,
+        String transactionChainId ) {
+
+        DOMStoreTransactionFactory factory = store;
+
+        if(!transactionChainId.isEmpty()) {
+            factory = transactionChains.get(transactionChainId);
+            if(factory == null){
+                DOMStoreTransactionChain transactionChain = store.createTransactionChain();
+                transactionChains.put(transactionChainId, transactionChain);
+                factory = transactionChain;
+            }
+        }
+
+        if(this.schemaContext == null){
+            throw new NullPointerException("schemaContext should not be null");
+        }
+
+        if (transactionType
             == TransactionProxy.TransactionType.READ_ONLY.ordinal()) {
+
             shardMBean.incrementReadOnlyTransactionCount();
+
             return getContext().actorOf(
-                ShardTransaction
-                    .props(store.newReadOnlyTransaction(), getSelf(),
-                        schemaContext), transactionId);
+                ShardTransaction.props(factory.newReadOnlyTransaction(), getSelf(),
+                        schemaContext,datastoreContext, shardMBean), transactionId.toString());
 
-        } else if (createTransaction.getTransactionType()
+        } else if (transactionType
             == TransactionProxy.TransactionType.READ_WRITE.ordinal()) {
+
             shardMBean.incrementReadWriteTransactionCount();
+
             return getContext().actorOf(
-                ShardTransaction
-                    .props(store.newReadWriteTransaction(), getSelf(),
-                        schemaContext), transactionId);
+                ShardTransaction.props(factory.newReadWriteTransaction(), getSelf(),
+                        schemaContext, datastoreContext, shardMBean), transactionId.toString());
 
 
-        } else if (createTransaction.getTransactionType()
+        } else if (transactionType
             == TransactionProxy.TransactionType.WRITE_ONLY.ordinal()) {
+
             shardMBean.incrementWriteOnlyTransactionCount();
+
             return getContext().actorOf(
-                ShardTransaction
-                    .props(store.newWriteOnlyTransaction(), getSelf(),
-                        schemaContext), transactionId);
+                ShardTransaction.props(factory.newWriteOnlyTransaction(), getSelf(),
+                        schemaContext, datastoreContext, shardMBean), transactionId.toString());
         } else {
             throw new IllegalArgumentException(
-                "CreateTransaction message has unidentified transaction type="
-                    + createTransaction.getTransactionType());
+                "Shard="+name + ":CreateTransaction message has unidentified transaction type="
+                    + transactionType);
         }
     }
 
     private void createTransaction(CreateTransaction createTransaction) {
+        createTransaction(createTransaction.getTransactionType(),
+            createTransaction.getTransactionId(), createTransaction.getTransactionChainId());
+    }
+
+    private ActorRef createTransaction(int transactionType, String remoteTransactionId, String transactionChainId) {
 
-        String transactionId = "shard-" + createTransaction.getTransactionId();
-        LOG.info("Creating transaction : {} ", transactionId);
+        ShardTransactionIdentifier transactionId =
+            ShardTransactionIdentifier.builder()
+                .remoteTransactionId(remoteTransactionId)
+                .build();
+        if(LOG.isDebugEnabled()) {
+            LOG.debug("Creating transaction : {} ", transactionId);
+        }
         ActorRef transactionActor =
-            createTypedTransactionActor(createTransaction, transactionId);
+            createTypedTransactionActor(transactionType, transactionId, transactionChainId);
 
         getSender()
             .tell(new CreateTransactionReply(
-                Serialization.serializedActorPath(transactionActor),
-                createTransaction.getTransactionId()).toSerializable(),
+                    Serialization.serializedActorPath(transactionActor),
+                    remoteTransactionId).toSerializable(),
                 getSelf());
+
+        return transactionActor;
     }
 
+    private void syncCommitTransaction(DOMStoreWriteTransaction transaction)
+        throws ExecutionException, InterruptedException {
+        DOMStoreThreePhaseCommitCohort commitCohort = transaction.ready();
+        commitCohort.preCommit().get();
+        commitCohort.commit().get();
+    }
+
+
     private void commit(final ActorRef sender, Object serialized) {
         Modification modification = MutableCompositeModification
             .fromSerializable(serialized, schemaContext);
         DOMStoreThreePhaseCommitCohort cohort =
             modificationToCohort.remove(serialized);
         if (cohort == null) {
-            LOG.error(
-                "Could not find cohort for modification : {}", modification);
-            LOG.info("Writing modification using a new transaction");
-            DOMStoreReadWriteTransaction transaction =
-                store.newReadWriteTransaction();
-            modification.apply(transaction);
-            DOMStoreThreePhaseCommitCohort commitCohort = transaction.ready();
-            ListenableFuture<Void> future =
-                commitCohort.preCommit();
-            try {
-                future.get();
-                future = commitCohort.commit();
-                future.get();
-            } catch (InterruptedException | ExecutionException e) {
-                shardMBean.incrementFailedTransactionsCount();
-                LOG.error("Failed to commit", e);
-                return;
-            }
-            //we want to just apply the recovery commit and return
-            shardMBean.incrementCommittedTransactionCount();
+            // If there's no cached cohort then we must be applying replicated state.
+            commitWithNewTransaction(serialized);
             return;
         }
 
-        final ListenableFuture<Void> future = cohort.commit();
-        final ActorRef self = getSelf();
-        future.addListener(new Runnable() {
+        if(sender == null) {
+            LOG.error("Commit failed. Sender cannot be null");
+            return;
+        }
+
+        ListenableFuture<Void> future = cohort.commit();
+
+        Futures.addCallback(future, new FutureCallback<Void>() {
             @Override
-            public void run() {
-                try {
-                    future.get();
-                        sender
-                            .tell(new CommitTransactionReply().toSerializable(),
-                                self);
-                        shardMBean.incrementCommittedTransactionCount();
-                        shardMBean.setLastCommittedTransactionTime(new Date());
+            public void onSuccess(Void v) {
+                sender.tell(new CommitTransactionReply().toSerializable(), getSelf());
+                shardMBean.incrementCommittedTransactionCount();
+                shardMBean.setLastCommittedTransactionTime(System.currentTimeMillis());
+            }
 
-                } catch (InterruptedException | ExecutionException e) {
-                    shardMBean.incrementFailedTransactionsCount();
-                    sender.tell(new akka.actor.Status.Failure(e),self);
-                }
+            @Override
+            public void onFailure(Throwable t) {
+                LOG.error(t, "An exception happened during commit");
+                shardMBean.incrementFailedTransactionsCount();
+                sender.tell(new akka.actor.Status.Failure(t), getSelf());
             }
-        }, getContext().dispatcher());
+        });
+
+    }
+
+    private void commitWithNewTransaction(Object modification) {
+        DOMStoreWriteTransaction tx = store.newWriteOnlyTransaction();
+        MutableCompositeModification.fromSerializable(modification, schemaContext).apply(tx);
+        try {
+            syncCommitTransaction(tx);
+            shardMBean.incrementCommittedTransactionCount();
+        } catch (InterruptedException | ExecutionException e) {
+            shardMBean.incrementFailedTransactionsCount();
+            LOG.error(e, "Failed to commit");
+        }
     }
 
     private void handleForwardedCommit(ForwardedCommitTransaction message) {
@@ -263,14 +395,21 @@ public class Shard extends RaftActor {
 
     private void updateSchemaContext(UpdateSchemaContext message) {
         this.schemaContext = message.getSchemaContext();
+        updateSchemaContext(message.getSchemaContext());
         store.onGlobalContextUpdated(message.getSchemaContext());
     }
 
+    @VisibleForTesting void updateSchemaContext(SchemaContext schemaContext) {
+        store.onGlobalContextUpdated(schemaContext);
+    }
+
     private void registerChangeListener(
         RegisterChangeListener registerChangeListener) {
 
-        LOG.debug("registerDataChangeListener for " + registerChangeListener
-            .getPath());
+        if(LOG.isDebugEnabled()) {
+            LOG.debug("registerDataChangeListener for {}", registerChangeListener
+                .getPath());
+        }
 
 
         ActorSelection dataChangeListenerPath = getContext()
@@ -289,73 +428,179 @@ public class Shard extends RaftActor {
         dataChangeListeners.add(dataChangeListenerPath);
 
         AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>
-            listener =
-            new DataChangeListenerProxy(schemaContext, dataChangeListenerPath);
+            listener = new DataChangeListenerProxy(schemaContext, dataChangeListenerPath);
 
-        org.opendaylight.yangtools.concepts.ListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>>
-            registration =
-            store.registerChangeListener(registerChangeListener.getPath(),
+        ListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>>
+            registration = store.registerChangeListener(registerChangeListener.getPath(),
                 listener, registerChangeListener.getScope());
         ActorRef listenerRegistration =
             getContext().actorOf(
                 DataChangeListenerRegistration.props(registration));
 
-        LOG.debug(
-            "registerDataChangeListener sending reply, listenerRegistrationPath = "
-                + listenerRegistration.path().toString());
+        if(LOG.isDebugEnabled()) {
+            LOG.debug(
+                "registerDataChangeListener sending reply, listenerRegistrationPath = {} "
+                , listenerRegistration.path().toString());
+        }
 
         getSender()
             .tell(new RegisterChangeListenerReply(listenerRegistration.path()),
                 getSelf());
     }
 
-    private void createTransactionChain() {
-        DOMStoreTransactionChain chain = store.createTransactionChain();
-        ActorRef transactionChain =
-            getContext().actorOf(
-                ShardTransactionChain.props(chain, schemaContext));
-        getSender()
-            .tell(new CreateTransactionChainReply(transactionChain.path())
-                    .toSerializable(),
-                getSelf());
+    private boolean isMetricsCaptureEnabled(){
+        CommonConfig config = new CommonConfig(getContext().system().settings().config());
+        return config.isMetricCaptureEnabled();
+    }
+
+    @Override
+    protected
+    void startLogRecoveryBatch(int maxBatchSize) {
+        currentLogRecoveryBatch = Lists.newArrayListWithCapacity(maxBatchSize);
+
+        if(LOG.isDebugEnabled()) {
+            LOG.debug("{} : starting log recovery batch with max size {}", persistenceId(), maxBatchSize);
+        }
+    }
+
+    @Override
+    protected void appendRecoveredLogEntry(Payload data) {
+        if (data instanceof CompositeModificationPayload) {
+            currentLogRecoveryBatch.add(((CompositeModificationPayload) data).getModification());
+        } else {
+            LOG.error("Unknown state received {} during recovery", data);
+        }
+    }
+
+    @Override
+    protected void applyRecoverySnapshot(ByteString snapshot) {
+        if(recoveryCoordinator == null) {
+            recoveryCoordinator = new ShardRecoveryCoordinator(persistenceId(), schemaContext);
+        }
+
+        recoveryCoordinator.submit(snapshot, store.newWriteOnlyTransaction());
+
+        if(LOG.isDebugEnabled()) {
+            LOG.debug("{} : submitted recovery sbapshot", persistenceId());
+        }
+    }
+
+    @Override
+    protected void applyCurrentLogRecoveryBatch() {
+        if(recoveryCoordinator == null) {
+            recoveryCoordinator = new ShardRecoveryCoordinator(persistenceId(), schemaContext);
+        }
+
+        recoveryCoordinator.submit(currentLogRecoveryBatch, store.newWriteOnlyTransaction());
+
+        if(LOG.isDebugEnabled()) {
+            LOG.debug("{} : submitted log recovery batch with size {}", persistenceId(),
+                    currentLogRecoveryBatch.size());
+        }
+    }
+
+    @Override
+    protected void onRecoveryComplete() {
+        if(recoveryCoordinator != null) {
+            Collection<DOMStoreWriteTransaction> txList = recoveryCoordinator.getTransactions();
+
+            if(LOG.isDebugEnabled()) {
+                LOG.debug("{} : recovery complete - committing {} Tx's", persistenceId(), txList.size());
+            }
+
+            for(DOMStoreWriteTransaction tx: txList) {
+                try {
+                    syncCommitTransaction(tx);
+                    shardMBean.incrementCommittedTransactionCount();
+                } catch (InterruptedException | ExecutionException e) {
+                    shardMBean.incrementFailedTransactionsCount();
+                    LOG.error(e, "Failed to commit");
+                }
+            }
+        }
+
+        recoveryCoordinator = null;
+        currentLogRecoveryBatch = null;
+        updateJournalStats();
     }
 
-    @Override protected void applyState(ActorRef clientActor, String identifier,
-        Object data) {
+    @Override
+    protected void applyState(ActorRef clientActor, String identifier, Object data) {
 
         if (data instanceof CompositeModificationPayload) {
-            Object modification =
-                ((CompositeModificationPayload) data).getModification();
+            Object modification = ((CompositeModificationPayload) data).getModification();
 
             if (modification != null) {
                 commit(clientActor, modification);
             } else {
-                LOG.error("modification is null - this is very unexpected");
+                LOG.error(
+                    "modification is null - this is very unexpected, clientActor = {}, identifier = {}",
+                    identifier, clientActor != null ? clientActor.path().toString() : null);
             }
 
-
         } else {
-            LOG.error("Unknown state received {}", data);
+            LOG.error("Unknown state received {} Class loader = {} CompositeNodeMod.ClassLoader = {}",
+                    data, data.getClass().getClassLoader(),
+                    CompositeModificationPayload.class.getClassLoader());
         }
 
+        updateJournalStats();
+
+    }
+
+    private void updateJournalStats() {
         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 
-        if(lastLogEntry != null){
+        if (lastLogEntry != null) {
             shardMBean.setLastLogIndex(lastLogEntry.getIndex());
             shardMBean.setLastLogTerm(lastLogEntry.getTerm());
         }
 
         shardMBean.setCommitIndex(getCommitIndex());
         shardMBean.setLastApplied(getLastApplied());
-
     }
 
-    @Override protected Object createSnapshot() {
-        throw new UnsupportedOperationException("createSnapshot");
+    @Override
+    protected void createSnapshot() {
+        if (createSnapshotTransaction == null) {
+
+            // Create a transaction. We are really going to treat the transaction as a worker
+            // so that this actor does not get block building the snapshot
+            createSnapshotTransaction = createTransaction(
+                TransactionProxy.TransactionType.READ_ONLY.ordinal(),
+                "createSnapshot", "");
+
+            createSnapshotTransaction.tell(
+                new ReadData(YangInstanceIdentifier.builder().build()).toSerializable(), self());
+
+        }
     }
 
-    @Override protected void applySnapshot(Object snapshot) {
-        throw new UnsupportedOperationException("applySnapshot");
+    @VisibleForTesting
+    @Override
+    protected void applySnapshot(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
+
+        LOG.info("Applying snapshot");
+        try {
+            DOMStoreWriteTransaction transaction = store.newWriteOnlyTransaction();
+            NormalizedNodeMessages.Node serializedNode = NormalizedNodeMessages.Node.parseFrom(snapshot);
+            NormalizedNode<?, ?> node = new NormalizedNodeToNodeCodec(schemaContext)
+                .decode(YangInstanceIdentifier.builder().build(), serializedNode);
+
+            // delete everything first
+            transaction.delete(YangInstanceIdentifier.builder().build());
+
+            // Add everything from the remote node back
+            transaction.write(YangInstanceIdentifier.builder().build(), node);
+            syncCommitTransaction(transaction);
+        } catch (InvalidProtocolBufferException | InterruptedException | ExecutionException e) {
+            LOG.error(e, "An exception occurred when applying snapshot");
+        } finally {
+            LOG.info("Done applying snapshot");
+        }
     }
 
     @Override protected void onStateChanged() {
@@ -364,25 +609,83 @@ public class Shard extends RaftActor {
                 .tell(new EnableNotification(isLeader()), getSelf());
         }
 
-        if (getLeaderId() != null) {
-            shardMBean.setLeader(getLeaderId());
-        }
-
         shardMBean.setRaftState(getRaftState().name());
         shardMBean.setCurrentTerm(getCurrentTerm());
+
+        // If this actor is no longer the leader close all the transaction chains
+        if(!isLeader()){
+            for(Map.Entry<String, DOMStoreTransactionChain> entry : transactionChains.entrySet()){
+                if(LOG.isDebugEnabled()) {
+                    LOG.debug(
+                        "onStateChanged: Closing transaction chain {} because shard {} is no longer the leader",
+                        entry.getKey(), getId());
+                }
+                entry.getValue().close();
+            }
+
+            transactionChains.clear();
+        }
+    }
+
+    @Override protected void onLeaderChanged(String oldLeader, String newLeader) {
+        shardMBean.setLeader(newLeader);
     }
 
     @Override public String persistenceId() {
-        return this.name;
+        return this.name.toString();
     }
 
+    private static class ShardCreator implements Creator<Shard> {
 
-    private static class ShardConfigParams extends DefaultConfigParamsImpl {
-        public static final FiniteDuration HEART_BEAT_INTERVAL =
-            new FiniteDuration(500, TimeUnit.MILLISECONDS);
+        private static final long serialVersionUID = 1L;
 
-        @Override public FiniteDuration getHeartBeatInterval() {
-            return HEART_BEAT_INTERVAL;
+        final ShardIdentifier name;
+        final Map<ShardIdentifier, String> peerAddresses;
+        final DatastoreContext datastoreContext;
+        final SchemaContext schemaContext;
+
+        ShardCreator(ShardIdentifier name, Map<ShardIdentifier, String> peerAddresses,
+                DatastoreContext datastoreContext, SchemaContext schemaContext) {
+            this.name = name;
+            this.peerAddresses = peerAddresses;
+            this.datastoreContext = datastoreContext;
+            this.schemaContext = schemaContext;
         }
+
+        @Override
+        public Shard create() throws Exception {
+            return new Shard(name, peerAddresses, datastoreContext, schemaContext);
+        }
+    }
+
+    @VisibleForTesting
+    NormalizedNode<?,?> readStore(YangInstanceIdentifier id)
+            throws ExecutionException, InterruptedException {
+        DOMStoreReadTransaction transaction = store.newReadOnlyTransaction();
+
+        CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> future =
+            transaction.read(id);
+
+        Optional<NormalizedNode<?, ?>> optional = future.get();
+        NormalizedNode<?, ?> node = optional.isPresent()? optional.get() : null;
+
+        transaction.close();
+
+        return node;
+    }
+
+    @VisibleForTesting
+    void writeToStore(YangInstanceIdentifier id, NormalizedNode<?,?> node)
+        throws ExecutionException, InterruptedException {
+        DOMStoreWriteTransaction transaction = store.newWriteOnlyTransaction();
+
+        transaction.write(id, node);
+
+        syncCommitTransaction(transaction);
+    }
+
+    @VisibleForTesting
+    ShardStats getShardMBean() {
+        return shardMBean;
     }
 }