X-Git-Url: https://git.opendaylight.org/gerrit/gitweb?a=blobdiff_plain;f=opendaylight%2Fmd-sal%2Fsal-distributed-datastore%2Fsrc%2Fmain%2Fjava%2Forg%2Fopendaylight%2Fcontroller%2Fcluster%2Fdatastore%2FShardManager.java;h=5874c5296f0ebd8d1b5085abd3797f6c77907618;hb=d4d59200f8c56551755c36fbbd2b4aa52defa5cb;hp=64c6821120f94f99a389c12700757a7b8c7266f5;hpb=86f71bd3f15ce34a9181bb01f0f71fc6979917c5;p=controller.git

diff --git a/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/ShardManager.java b/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/ShardManager.java
index 64c6821120..a91109c64b 100644
--- a/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/ShardManager.java
+++ b/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/ShardManager.java
@@ -8,29 +8,101 @@
 
 package org.opendaylight.controller.cluster.datastore;
 
+import static akka.pattern.Patterns.ask;
 import akka.actor.ActorPath;
 import akka.actor.ActorRef;
 import akka.actor.Address;
+import akka.actor.Cancellable;
 import akka.actor.OneForOneStrategy;
+import akka.actor.PoisonPill;
 import akka.actor.Props;
+import akka.actor.Status;
 import akka.actor.SupervisorStrategy;
 import akka.cluster.ClusterEvent;
-import akka.japi.Creator;
+import akka.dispatch.OnComplete;
 import akka.japi.Function;
+import akka.persistence.RecoveryCompleted;
+import akka.persistence.SaveSnapshotFailure;
+import akka.persistence.SaveSnapshotSuccess;
+import akka.persistence.SnapshotOffer;
+import akka.persistence.SnapshotSelectionCriteria;
+import akka.serialization.Serialization;
+import akka.util.Timeout;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Objects;
+import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
+import com.google.common.base.Strings;
+import com.google.common.base.Supplier;
+import com.google.common.collect.Sets;
+import java.io.ByteArrayInputStream;
+import java.io.ObjectInputStream;
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import org.apache.commons.lang3.SerializationUtils;
+import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActorWithMetering;
+import org.opendaylight.controller.cluster.datastore.config.Configuration;
+import org.opendaylight.controller.cluster.datastore.config.ModuleShardConfiguration;
+import org.opendaylight.controller.cluster.datastore.exceptions.AlreadyExistsException;
+import org.opendaylight.controller.cluster.datastore.exceptions.NoShardLeaderException;
+import org.opendaylight.controller.cluster.datastore.exceptions.NotInitializedException;
+import org.opendaylight.controller.cluster.datastore.exceptions.PrimaryNotFoundException;
+import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
+import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shardmanager.ShardManagerInfo;
+import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shardmanager.ShardManagerInfoMBean;
+import org.opendaylight.controller.cluster.datastore.messages.ActorInitialized;
+import org.opendaylight.controller.cluster.datastore.messages.AddShardReplica;
+import org.opendaylight.controller.cluster.datastore.messages.CreateShard;
+import org.opendaylight.controller.cluster.datastore.messages.DatastoreSnapshot;
 import org.opendaylight.controller.cluster.datastore.messages.FindLocalShard;
 import org.opendaylight.controller.cluster.datastore.messages.FindPrimary;
+import org.opendaylight.controller.cluster.datastore.messages.LocalPrimaryShardFound;
 import org.opendaylight.controller.cluster.datastore.messages.LocalShardFound;
 import org.opendaylight.controller.cluster.datastore.messages.LocalShardNotFound;
 import org.opendaylight.controller.cluster.datastore.messages.PeerAddressResolved;
-import org.opendaylight.controller.cluster.datastore.messages.PrimaryFound;
-import org.opendaylight.controller.cluster.datastore.messages.PrimaryNotFound;
+import org.opendaylight.controller.cluster.datastore.messages.PeerDown;
+import org.opendaylight.controller.cluster.datastore.messages.PeerUp;
+import org.opendaylight.controller.cluster.datastore.messages.RemoteFindPrimary;
+import org.opendaylight.controller.cluster.datastore.messages.RemotePrimaryShardFound;
+import org.opendaylight.controller.cluster.datastore.messages.RemoveShardReplica;
+import org.opendaylight.controller.cluster.datastore.messages.ShardLeaderStateChanged;
+import org.opendaylight.controller.cluster.datastore.messages.SwitchShardBehavior;
 import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContext;
+import org.opendaylight.controller.cluster.datastore.utils.Dispatchers;
+import org.opendaylight.controller.cluster.datastore.utils.PrimaryShardInfoFutureCache;
+import org.opendaylight.controller.cluster.notifications.RegisterRoleChangeListener;
+import org.opendaylight.controller.cluster.notifications.RoleChangeNotification;
+import org.opendaylight.controller.cluster.raft.RaftState;
+import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
+import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
+import org.opendaylight.controller.cluster.raft.client.messages.GetSnapshot;
+import org.opendaylight.controller.cluster.raft.messages.AddServer;
+import org.opendaylight.controller.cluster.raft.messages.AddServerReply;
+import org.opendaylight.controller.cluster.raft.messages.RemoveServer;
+import org.opendaylight.controller.cluster.raft.messages.RemoveServerReply;
+import org.opendaylight.controller.cluster.raft.messages.ServerChangeStatus;
+import org.opendaylight.controller.cluster.raft.messages.ServerRemoved;
+import org.opendaylight.controller.cluster.raft.policy.DisableElectionsRaftPolicy;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
+import org.opendaylight.yangtools.yang.model.api.SchemaContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import scala.concurrent.Future;
 import scala.concurrent.duration.Duration;
-
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
+import scala.concurrent.duration.FiniteDuration;
 
 /**
  * The ShardManager has the following jobs,
@@ -41,12 +113,9 @@ import java.util.Map;
  * <li> Monitor the cluster members and store their addresses
  * <ul>
  */
-public class ShardManager extends AbstractUntypedActor {
+public class ShardManager extends AbstractUntypedPersistentActorWithMetering {
 
-    // Stores a mapping between a member name and the address of the member
-    // Member names look like "member-1", "member-2" etc and are as specified
-    // in configuration
-    private final Map<String, Address> memberNameToAddress = new HashMap<>();
+    private static final Logger LOG = LoggerFactory.getLogger(ShardManager.class);
 
     // Stores a mapping between a shard name and it's corresponding information
     // Shard names look like inventory, topology etc and are as specified in
@@ -61,263 +130,1679 @@ public class ShardManager extends AbstractUntypedActor {
 
     private final Configuration configuration;
 
+    private final String shardDispatcherPath;
+
+    private final ShardManagerInfo mBean;
+
+    private DatastoreContextFactory datastoreContextFactory;
+
+    private final CountDownLatch waitTillReadyCountdownLatch;
+
+    private final PrimaryShardInfoFutureCache primaryShardInfoCache;
+
+    private final ShardPeerAddressResolver peerAddressResolver;
+
+    private SchemaContext schemaContext;
+
+    private DatastoreSnapshot restoreFromSnapshot;
+
+    private ShardManagerSnapshot currentSnapshot;
+
+    private final Set<String> shardReplicaOperationsInProgress = new HashSet<>();
+
+    private final String persistenceId;
+
     /**
-     * @param type defines the kind of data that goes into shards created by this shard manager. Examples of type would be
-     *             configuration or operational
      */
-    private ShardManager(String type, ClusterWrapper cluster, Configuration configuration) {
+    protected ShardManager(AbstractBuilder<?> builder) {
+
+        this.cluster = builder.cluster;
+        this.configuration = builder.configuration;
+        this.datastoreContextFactory = builder.datastoreContextFactory;
+        this.type = builder.datastoreContextFactory.getBaseDatastoreContext().getDataStoreName();
+        this.shardDispatcherPath =
+                new Dispatchers(context().system().dispatchers()).getDispatcherPath(Dispatchers.DispatcherType.Shard);
+        this.waitTillReadyCountdownLatch = builder.waitTillReadyCountdownLatch;
+        this.primaryShardInfoCache = builder.primaryShardInfoCache;
+        this.restoreFromSnapshot = builder.restoreFromSnapshot;
+
+        String possiblePersistenceId = datastoreContextFactory.getBaseDatastoreContext().getShardManagerPersistenceId();
+        persistenceId = possiblePersistenceId != null ? possiblePersistenceId : "shard-manager-" + type;
 
-        this.type = Preconditions.checkNotNull(type, "type should not be null");
-        this.cluster = Preconditions.checkNotNull(cluster, "cluster should not be null");
-        this.configuration = Preconditions.checkNotNull(configuration, "configuration should not be null");
+        peerAddressResolver = new ShardPeerAddressResolver(type, cluster.getCurrentMemberName());
 
         // Subscribe this actor to cluster member events
         cluster.subscribeToMemberEvents(getSelf());
 
-        // Create all the local Shards and make them a child of the ShardManager
-        // TODO: This may need to be initiated when we first get the schema context
-        createLocalShards();
+        List<String> localShardActorNames = new ArrayList<>();
+        mBean = ShardManagerInfo.createShardManagerMBean(cluster.getCurrentMemberName(),
+                "shard-manager-" + this.type,
+                datastoreContextFactory.getBaseDatastoreContext().getDataStoreMXBeanType(),
+                localShardActorNames);
+        mBean.setShardManager(this);
     }
 
-    public static Props props(final String type,
-        final ClusterWrapper cluster,
-        final Configuration configuration) {
-        return Props.create(new Creator<ShardManager>() {
+    @Override
+    public void postStop() {
+        LOG.info("Stopping ShardManager");
 
-            @Override
-            public ShardManager create() throws Exception {
-                return new ShardManager(type, cluster, configuration);
-            }
-        });
+        mBean.unregisterMBean();
     }
 
-
     @Override
-    public void handleReceive(Object message) throws Exception {
-        if (message.getClass().equals(FindPrimary.SERIALIZABLE_CLASS)) {
-            findPrimary(
-                FindPrimary.fromSerializable(message));
+    public void handleCommand(Object message) throws Exception {
+        if (message  instanceof FindPrimary) {
+            findPrimary((FindPrimary)message);
         } else if(message instanceof FindLocalShard){
             findLocalShard((FindLocalShard) message);
         } else if (message instanceof UpdateSchemaContext) {
             updateSchemaContext(message);
+        } else if(message instanceof ActorInitialized) {
+            onActorInitialized(message);
         } else if (message instanceof ClusterEvent.MemberUp){
             memberUp((ClusterEvent.MemberUp) message);
+        } else if (message instanceof ClusterEvent.MemberExited){
+            memberExited((ClusterEvent.MemberExited) message);
         } else if(message instanceof ClusterEvent.MemberRemoved) {
             memberRemoved((ClusterEvent.MemberRemoved) message);
         } else if(message instanceof ClusterEvent.UnreachableMember) {
-            ignoreMessage(message);
-        } else{
-          throw new Exception ("Not recognized message received, message="+message);
+            memberUnreachable((ClusterEvent.UnreachableMember)message);
+        } else if(message instanceof ClusterEvent.ReachableMember) {
+            memberReachable((ClusterEvent.ReachableMember) message);
+        } else if(message instanceof DatastoreContextFactory) {
+            onDatastoreContextFactory((DatastoreContextFactory)message);
+        } else if(message instanceof RoleChangeNotification) {
+            onRoleChangeNotification((RoleChangeNotification) message);
+        } else if(message instanceof FollowerInitialSyncUpStatus){
+            onFollowerInitialSyncStatus((FollowerInitialSyncUpStatus) message);
+        } else if(message instanceof ShardNotInitializedTimeout) {
+            onShardNotInitializedTimeout((ShardNotInitializedTimeout)message);
+        } else if(message instanceof ShardLeaderStateChanged) {
+            onLeaderStateChanged((ShardLeaderStateChanged) message);
+        } else if(message instanceof SwitchShardBehavior){
+            onSwitchShardBehavior((SwitchShardBehavior) message);
+        } else if(message instanceof CreateShard) {
+            onCreateShard((CreateShard)message);
+        } else if(message instanceof AddShardReplica){
+            onAddShardReplica((AddShardReplica)message);
+        } else if(message instanceof ForwardedAddServerReply) {
+            ForwardedAddServerReply msg = (ForwardedAddServerReply)message;
+            onAddServerReply(msg.shardInfo, msg.addServerReply, getSender(), msg.leaderPath,
+                    msg.removeShardOnFailure);
+        } else if(message instanceof ForwardedAddServerFailure) {
+            ForwardedAddServerFailure msg = (ForwardedAddServerFailure)message;
+            onAddServerFailure(msg.shardName, msg.failureMessage, msg.failure, getSender(), msg.removeShardOnFailure);
+        } else if(message instanceof PrimaryShardFoundForContext) {
+            PrimaryShardFoundForContext primaryShardFoundContext = (PrimaryShardFoundForContext)message;
+            onPrimaryShardFoundContext(primaryShardFoundContext);
+        } else if(message instanceof RemoveShardReplica) {
+            onRemoveShardReplica((RemoveShardReplica) message);
+        } else if(message instanceof WrappedShardResponse){
+            onWrappedShardResponse((WrappedShardResponse) message);
+        } else if(message instanceof GetSnapshot) {
+            onGetSnapshot();
+        } else if(message instanceof ServerRemoved){
+            onShardReplicaRemoved((ServerRemoved) message);
+        } else if (message instanceof SaveSnapshotSuccess) {
+            onSaveSnapshotSuccess((SaveSnapshotSuccess)message);
+        } else if (message instanceof SaveSnapshotFailure) {
+            LOG.error("{}: SaveSnapshotFailure received for saving snapshot of shards",
+                    persistenceId(), ((SaveSnapshotFailure) message).cause());
+        } else {
+            unknownMessage(message);
+        }
+    }
+
+    private void onWrappedShardResponse(WrappedShardResponse message) {
+        if (message.getResponse() instanceof RemoveServerReply) {
+            onRemoveServerReply(getSender(), message.getShardName(), (RemoveServerReply) message.getResponse());
         }
+    }
 
+    private void onRemoveServerReply(ActorRef originalSender, String shardName, RemoveServerReply response) {
+        shardReplicaOperationsInProgress.remove(shardName);
+        originalSender.tell(new Status.Success(null), self());
     }
 
-    private void findLocalShard(FindLocalShard message) {
-        ShardInformation shardInformation =
-            localShards.get(message.getShardName());
+    private void onPrimaryShardFoundContext(PrimaryShardFoundForContext primaryShardFoundContext) {
+        if(primaryShardFoundContext.getContextMessage() instanceof AddShardReplica) {
+            addShard(primaryShardFoundContext.getShardName(), primaryShardFoundContext.getRemotePrimaryShardFound(),
+                    getSender());
+        } else if(primaryShardFoundContext.getContextMessage() instanceof RemoveShardReplica){
+            removeShardReplica((RemoveShardReplica) primaryShardFoundContext.getContextMessage(),
+                    primaryShardFoundContext.getShardName(), primaryShardFoundContext.getPrimaryPath(), getSender());
+        }
+    }
 
-        if(shardInformation != null){
-            getSender().tell(new LocalShardFound(shardInformation.getActor()), getSelf());
+    private void removeShardReplica(RemoveShardReplica contextMessage, final String shardName, final String primaryPath,
+            final ActorRef sender) {
+        if(isShardReplicaOperationInProgress(shardName, sender)) {
             return;
         }
 
-        getSender().tell(new LocalShardNotFound(message.getShardName()), getSelf());
+        shardReplicaOperationsInProgress.add(shardName);
+
+        final ShardIdentifier shardId = getShardIdentifier(contextMessage.getMemberName(), shardName);
+
+        final DatastoreContext datastoreContext = newShardDatastoreContextBuilder(shardName).build();
+
+        //inform ShardLeader to remove this shard as a replica by sending an RemoveServer message
+        LOG.debug ("{}: Sending RemoveServer message to peer {} for shard {}", persistenceId(),
+                primaryPath, shardId);
+
+        Timeout removeServerTimeout = new Timeout(datastoreContext.getShardLeaderElectionTimeout().
+                duration());
+        Future<Object> futureObj = ask(getContext().actorSelection(primaryPath),
+                new RemoveServer(shardId.toString()), removeServerTimeout);
+
+        futureObj.onComplete(new OnComplete<Object>() {
+            @Override
+            public void onComplete(Throwable failure, Object response) {
+                if (failure != null) {
+                    String msg = String.format("RemoveServer request to leader %s for shard %s failed",
+                            primaryPath, shardName);
+
+                    LOG.debug ("{}: {}", persistenceId(), msg, failure);
+
+                    // FAILURE
+                    sender.tell(new Status.Failure(new RuntimeException(msg, failure)), self());
+                } else {
+                    // SUCCESS
+                    self().tell(new WrappedShardResponse(shardName, response), sender);
+                }
+            }
+        }, new Dispatchers(context().system().dispatchers()).getDispatcher(Dispatchers.DispatcherType.Client));
     }
 
-    private void ignoreMessage(Object message){
-        LOG.debug("Unhandled message : " + message);
+    private void onShardReplicaRemoved(ServerRemoved message) {
+        final ShardIdentifier shardId = new ShardIdentifier.Builder().fromShardIdString(message.getServerId()).build();
+        final ShardInformation shardInformation = localShards.remove(shardId.getShardName());
+        if(shardInformation == null) {
+            LOG.debug("{} : Shard replica {} is not present in list", persistenceId(), shardId.toString());
+            return;
+        } else if(shardInformation.getActor() != null) {
+            LOG.debug("{} : Sending PoisonPill to Shard actor {}", persistenceId(), shardInformation.getActor());
+            shardInformation.getActor().tell(PoisonPill.getInstance(), self());
+        }
+        LOG.debug("{} : Local Shard replica for shard {} has been removed", persistenceId(), shardId.getShardName());
+        persistShardList();
     }
 
-    private void memberRemoved(ClusterEvent.MemberRemoved message) {
-        memberNameToAddress.remove(message.member().roles().head());
+    private void onGetSnapshot() {
+        LOG.debug("{}: onGetSnapshot", persistenceId());
+
+        List<String> notInitialized = null;
+        for(ShardInformation shardInfo: localShards.values()) {
+            if(!shardInfo.isShardInitialized()) {
+                if(notInitialized == null) {
+                    notInitialized = new ArrayList<>();
+                }
+
+                notInitialized.add(shardInfo.getShardName());
+            }
+        }
+
+        if(notInitialized != null) {
+            getSender().tell(new akka.actor.Status.Failure(new IllegalStateException(String.format(
+                    "%d shard(s) %s are not initialized", notInitialized.size(), notInitialized))), getSelf());
+            return;
+        }
+
+        byte[] shardManagerSnapshot = null;
+        if(currentSnapshot != null) {
+            shardManagerSnapshot = SerializationUtils.serialize(currentSnapshot);
+        }
+
+        ActorRef replyActor = getContext().actorOf(ShardManagerGetSnapshotReplyActor.props(
+                new ArrayList<>(localShards.keySet()), type, shardManagerSnapshot , getSender(), persistenceId(),
+                datastoreContextFactory.getBaseDatastoreContext().getShardInitializationTimeout().duration()));
+
+        for(ShardInformation shardInfo: localShards.values()) {
+            shardInfo.getActor().tell(GetSnapshot.INSTANCE, replyActor);
+        }
     }
 
-    private void memberUp(ClusterEvent.MemberUp message) {
-        String memberName = message.member().roles().head();
+    private void onCreateShard(CreateShard createShard) {
+        LOG.debug("{}: onCreateShard: {}", persistenceId(), createShard);
 
-        memberNameToAddress.put(memberName , message.member().address());
+        Object reply;
+        try {
+            String shardName = createShard.getModuleShardConfig().getShardName();
+            if(localShards.containsKey(shardName)) {
+                LOG.debug("{}: Shard {} already exists", persistenceId(), shardName);
+                reply = new akka.actor.Status.Success(String.format("Shard with name %s already exists", shardName));
+            } else {
+                doCreateShard(createShard);
+                reply = new akka.actor.Status.Success(null);
+            }
+        } catch (Exception e) {
+            LOG.error("{}: onCreateShard failed", persistenceId(), e);
+            reply = new akka.actor.Status.Failure(e);
+        }
 
-        for(ShardInformation info : localShards.values()){
-            String shardName = info.getShardName();
-            info.updatePeerAddress(getShardActorName(memberName, shardName),
-                getShardActorPath(shardName, memberName));
+        if(getSender() != null && !getContext().system().deadLetters().equals(getSender())) {
+            getSender().tell(reply, getSelf());
         }
     }
 
-    /**
-     * Notifies all the local shards of a change in the schema context
-     *
-     * @param message
-     */
-    private void updateSchemaContext(Object message) {
-        for(ShardInformation info : localShards.values()){
-            info.getActor().tell(message,getSelf());
+    private void doCreateShard(CreateShard createShard) {
+        ModuleShardConfiguration moduleShardConfig = createShard.getModuleShardConfig();
+        String shardName = moduleShardConfig.getShardName();
+
+        configuration.addModuleShardConfiguration(moduleShardConfig);
+
+        DatastoreContext shardDatastoreContext = createShard.getDatastoreContext();
+        if(shardDatastoreContext == null) {
+            shardDatastoreContext = newShardDatastoreContext(shardName);
+        } else {
+            shardDatastoreContext = DatastoreContext.newBuilderFrom(shardDatastoreContext).shardPeerAddressResolver(
+                    peerAddressResolver).build();
+        }
+
+        ShardIdentifier shardId = getShardIdentifier(cluster.getCurrentMemberName(), shardName);
+
+        boolean shardWasInRecoveredSnapshot = currentSnapshot != null &&
+                currentSnapshot.getShardList().contains(shardName);
+
+        Map<String, String> peerAddresses;
+        boolean isActiveMember;
+        if(shardWasInRecoveredSnapshot || configuration.getMembersFromShardName(shardName).
+                contains(cluster.getCurrentMemberName())) {
+            peerAddresses = getPeerAddresses(shardName);
+            isActiveMember = true;
+        } else {
+            // The local member is not in the static shard member configuration and the shard did not
+            // previously exist (ie !shardWasInRecoveredSnapshot). In this case we'll create
+            // the shard with no peers and with elections disabled so it stays as follower. A
+            // subsequent AddServer request will be needed to make it an active member.
+            isActiveMember = false;
+            peerAddresses = Collections.emptyMap();
+            shardDatastoreContext = DatastoreContext.newBuilderFrom(shardDatastoreContext).
+                    customRaftPolicyImplementation(DisableElectionsRaftPolicy.class.getName()).build();
+        }
+
+        LOG.debug("{} doCreateShard: shardId: {}, memberNames: {}, peerAddresses: {}, isActiveMember: {}",
+                persistenceId(), shardId, moduleShardConfig.getShardMemberNames(), peerAddresses,
+                isActiveMember);
+
+        ShardInformation info = new ShardInformation(shardName, shardId, peerAddresses,
+                shardDatastoreContext, createShard.getShardBuilder(), peerAddressResolver);
+        info.setActiveMember(isActiveMember);
+        localShards.put(info.getShardName(), info);
+
+        mBean.addLocalShard(shardId.toString());
+
+        if(schemaContext != null) {
+            info.setActor(newShardActor(schemaContext, info));
         }
     }
 
-    private void findPrimary(FindPrimary message) {
-        String shardName = message.getShardName();
+    private DatastoreContext.Builder newShardDatastoreContextBuilder(String shardName) {
+        return DatastoreContext.newBuilderFrom(datastoreContextFactory.getShardDatastoreContext(shardName)).
+                shardPeerAddressResolver(peerAddressResolver);
+    }
 
-        List<String> members =
-            configuration.getMembersFromShardName(shardName);
+    private DatastoreContext newShardDatastoreContext(String shardName) {
+        return newShardDatastoreContextBuilder(shardName).build();
+    }
 
-        // First see if the there is a local replica for the shard
-        ShardInformation info = localShards.get(shardName);
-        if(info != null) {
-            ActorPath shardPath = info.getActorPath();
-            if (shardPath != null) {
-                getSender()
-                    .tell(
-                        new PrimaryFound(shardPath.toString()).toSerializable(),
-                        getSelf());
-                return;
+    private void checkReady(){
+        if (isReadyWithLeaderId()) {
+            LOG.info("{}: All Shards are ready - data store {} is ready, available count is {}",
+                    persistenceId(), type, waitTillReadyCountdownLatch.getCount());
+
+            waitTillReadyCountdownLatch.countDown();
+        }
+    }
+
+    private void onLeaderStateChanged(ShardLeaderStateChanged leaderStateChanged) {
+        LOG.info("{}: Received LeaderStateChanged message: {}", persistenceId(), leaderStateChanged);
+
+        ShardInformation shardInformation = findShardInformation(leaderStateChanged.getMemberId());
+        if(shardInformation != null) {
+            shardInformation.setLocalDataTree(leaderStateChanged.getLocalShardDataTree());
+            shardInformation.setLeaderVersion(leaderStateChanged.getLeaderPayloadVersion());
+            if(shardInformation.setLeaderId(leaderStateChanged.getLeaderId())) {
+                primaryShardInfoCache.remove(shardInformation.getShardName());
             }
+
+            checkReady();
+        } else {
+            LOG.debug("No shard found with member Id {}", leaderStateChanged.getMemberId());
+        }
+    }
+
+    private void onShardNotInitializedTimeout(ShardNotInitializedTimeout message) {
+        ShardInformation shardInfo = message.getShardInfo();
+
+        LOG.debug("{}: Received ShardNotInitializedTimeout message for shard {}", persistenceId(),
+                shardInfo.getShardName());
+
+        shardInfo.removeOnShardInitialized(message.getOnShardInitialized());
+
+        if(!shardInfo.isShardInitialized()) {
+            LOG.debug("{}: Returning NotInitializedException for shard {}", persistenceId(), shardInfo.getShardName());
+            message.getSender().tell(createNotInitializedException(shardInfo.shardId), getSelf());
+        } else {
+            LOG.debug("{}: Returning NoShardLeaderException for shard {}", persistenceId(), shardInfo.getShardName());
+            message.getSender().tell(createNoShardLeaderException(shardInfo.shardId), getSelf());
         }
+    }
 
-        if(cluster.getCurrentMemberName() != null) {
-            members.remove(cluster.getCurrentMemberName());
+    private void onFollowerInitialSyncStatus(FollowerInitialSyncUpStatus status) {
+        LOG.info("{} Received follower initial sync status for {} status sync done {}", persistenceId(),
+                status.getName(), status.isInitialSyncDone());
+
+        ShardInformation shardInformation = findShardInformation(status.getName());
+
+        if(shardInformation != null) {
+            shardInformation.setFollowerSyncStatus(status.isInitialSyncDone());
+
+            mBean.setSyncStatus(isInSync());
         }
 
-        // There is no way for us to figure out the primary (for now) so assume
-        // that one of the remote nodes is a primary
-        for(String memberName : members) {
-            Address address = memberNameToAddress.get(memberName);
-            if(address != null){
-                String path =
-                    getShardActorPath(shardName, memberName);
-                getSender().tell(new PrimaryFound(path).toSerializable(), getSelf());
-                return;
-            }
+    }
+
+    private void onRoleChangeNotification(RoleChangeNotification roleChanged) {
+        LOG.info("{}: Received role changed for {} from {} to {}", persistenceId(), roleChanged.getMemberId(),
+                roleChanged.getOldRole(), roleChanged.getNewRole());
+
+        ShardInformation shardInformation = findShardInformation(roleChanged.getMemberId());
+        if(shardInformation != null) {
+            shardInformation.setRole(roleChanged.getNewRole());
+            checkReady();
+            mBean.setSyncStatus(isInSync());
         }
-        getSender().tell(new PrimaryNotFound(shardName).toSerializable(), getSelf());
     }
 
-    private String getShardActorPath(String shardName, String memberName) {
-        Address address = memberNameToAddress.get(memberName);
-        if(address != null) {
-            return address.toString() + "/user/shardmanager-" + this.type + "/"
-                + getShardActorName(
-                memberName, shardName);
+
+    private ShardInformation findShardInformation(String memberId) {
+        for(ShardInformation info : localShards.values()){
+            if(info.getShardId().toString().equals(memberId)){
+                return info;
+            }
         }
+
         return null;
     }
 
-    /**
-     * Construct the name of the shard actor given the name of the member on
-     * which the shard resides and the name of the shard
-     *
-     * @param memberName
-     * @param shardName
-     * @return
-     */
-    private String getShardActorName(String memberName, String shardName){
-        return memberName + "-shard-" + shardName + "-" + this.type;
+    private boolean isReadyWithLeaderId() {
+        boolean isReady = true;
+        for (ShardInformation info : localShards.values()) {
+            if(!info.isShardReadyWithLeaderId()){
+                isReady = false;
+                break;
+            }
+        }
+        return isReady;
     }
 
-    /**
-     * Create shards that are local to the member on which the ShardManager
-     * runs
-     *
-     */
-    private void createLocalShards() {
-        String memberName = this.cluster.getCurrentMemberName();
-        List<String> memberShardNames =
-            this.configuration.getMemberShardNames(memberName);
+    private boolean isInSync(){
+        for (ShardInformation info : localShards.values()) {
+            if(!info.isInSync()){
+                return false;
+            }
+        }
+        return true;
+    }
 
-        for(String shardName : memberShardNames){
-            String shardActorName = getShardActorName(memberName, shardName);
-            Map<String, String> peerAddresses = getPeerAddresses(shardName);
-            ActorRef actor = getContext()
-                .actorOf(Shard.props(shardActorName, peerAddresses),
-                    shardActorName);
-            localShards.put(shardName, new ShardInformation(shardName, actor, peerAddresses));
+    private void onActorInitialized(Object message) {
+        final ActorRef sender = getSender();
+
+        if (sender == null) {
+            return; //why is a non-actor sending this message? Just ignore.
         }
 
+        String actorName = sender.path().name();
+        //find shard name from actor name; actor name is stringified shardId
+        ShardIdentifier shardId = ShardIdentifier.builder().fromShardIdString(actorName).build();
+
+        if (shardId.getShardName() == null) {
+            return;
+        }
+
+        markShardAsInitialized(shardId.getShardName());
     }
 
-    /**
-     * Given the name of the shard find the addresses of all it's peers
-     *
-     * @param shardName
-     * @return
-     */
-    private Map<String, String> getPeerAddresses(String shardName){
+    private void markShardAsInitialized(String shardName) {
+        LOG.debug("{}: Initializing shard [{}]", persistenceId(), shardName);
 
-        Map<String, String> peerAddresses = new HashMap<>();
+        ShardInformation shardInformation = localShards.get(shardName);
+        if (shardInformation != null) {
+            shardInformation.setActorInitialized();
 
-        List<String> members =
-            this.configuration.getMembersFromShardName(shardName);
+            shardInformation.getActor().tell(new RegisterRoleChangeListener(), self());
+        }
+    }
 
-        String currentMemberName = this.cluster.getCurrentMemberName();
+    @Override
+    protected void handleRecover(Object message) throws Exception {
+        if (message instanceof RecoveryCompleted) {
+            onRecoveryCompleted();
+        } else if (message instanceof SnapshotOffer) {
+            applyShardManagerSnapshot((ShardManagerSnapshot)((SnapshotOffer) message).snapshot());
+        }
+    }
+
+    private void onRecoveryCompleted() {
+        LOG.info("Recovery complete : {}", persistenceId());
+
+        // We no longer persist SchemaContext modules so delete all the prior messages from the akka
+        // journal on upgrade from Helium.
+        deleteMessages(lastSequenceNr());
+
+        if(currentSnapshot == null && restoreFromSnapshot != null &&
+                restoreFromSnapshot.getShardManagerSnapshot() != null) {
+            try(ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(
+                    restoreFromSnapshot.getShardManagerSnapshot()))) {
+                ShardManagerSnapshot snapshot = (ShardManagerSnapshot) ois.readObject();
 
-        for(String memberName : members){
-            if(!currentMemberName.equals(memberName)){
-                String shardActorName = getShardActorName(memberName, shardName);
-                String path =
-                    getShardActorPath(shardName, currentMemberName);
-                peerAddresses.put(shardActorName, path);
+                LOG.debug("{}: Deserialized restored ShardManagerSnapshot: {}", persistenceId(), snapshot);
+
+                applyShardManagerSnapshot(snapshot);
+            } catch(Exception e) {
+                LOG.error("{}: Error deserializing restored ShardManagerSnapshot", persistenceId(), e);
             }
         }
-        return peerAddresses;
+
+        createLocalShards();
     }
 
+    private void findLocalShard(FindLocalShard message) {
+        final ShardInformation shardInformation = localShards.get(message.getShardName());
 
-    @Override
-    public SupervisorStrategy supervisorStrategy() {
-        return new OneForOneStrategy(10, Duration.create("1 minute"),
-            new Function<Throwable, SupervisorStrategy.Directive>() {
-                @Override
-                public SupervisorStrategy.Directive apply(Throwable t) {
-                    return SupervisorStrategy.resume();
+        if(shardInformation == null){
+            getSender().tell(new LocalShardNotFound(message.getShardName()), getSelf());
+            return;
+        }
+
+        sendResponse(shardInformation, message.isWaitUntilInitialized(), false, new Supplier<Object>() {
+            @Override
+            public Object get() {
+                return new LocalShardFound(shardInformation.getActor());
+            }
+        });
+    }
+
+    private void sendResponse(ShardInformation shardInformation, boolean doWait,
+            boolean wantShardReady, final Supplier<Object> messageSupplier) {
+        if (!shardInformation.isShardInitialized() || (wantShardReady && !shardInformation.isShardReadyWithLeaderId())) {
+            if(doWait) {
+                final ActorRef sender = getSender();
+                final ActorRef self = self();
+
+                Runnable replyRunnable = new Runnable() {
+                    @Override
+                    public void run() {
+                        sender.tell(messageSupplier.get(), self);
+                    }
+                };
+
+                OnShardInitialized onShardInitialized = wantShardReady ? new OnShardReady(replyRunnable) :
+                    new OnShardInitialized(replyRunnable);
+
+                shardInformation.addOnShardInitialized(onShardInitialized);
+
+                FiniteDuration timeout = shardInformation.getDatastoreContext().getShardInitializationTimeout().duration();
+                if(shardInformation.isShardInitialized()) {
+                    // If the shard is already initialized then we'll wait enough time for the shard to
+                    // elect a leader, ie 2 times the election timeout.
+                    timeout = FiniteDuration.create(shardInformation.getDatastoreContext().getShardRaftConfig()
+                            .getElectionTimeOutInterval().toMillis() * 2, TimeUnit.MILLISECONDS);
                 }
+
+                LOG.debug("{}: Scheduling {} ms timer to wait for shard {}", persistenceId(), timeout.toMillis(),
+                        shardInformation.getShardName());
+
+                Cancellable timeoutSchedule = getContext().system().scheduler().scheduleOnce(
+                        timeout, getSelf(),
+                        new ShardNotInitializedTimeout(shardInformation, onShardInitialized, sender),
+                        getContext().dispatcher(), getSelf());
+
+                onShardInitialized.setTimeoutSchedule(timeoutSchedule);
+
+            } else if (!shardInformation.isShardInitialized()) {
+                LOG.debug("{}: Returning NotInitializedException for shard {}", persistenceId(),
+                        shardInformation.getShardName());
+                getSender().tell(createNotInitializedException(shardInformation.shardId), getSelf());
+            } else {
+                LOG.debug("{}: Returning NoShardLeaderException for shard {}", persistenceId(),
+                        shardInformation.getShardName());
+                getSender().tell(createNoShardLeaderException(shardInformation.shardId), getSelf());
             }
-        );
 
+            return;
+        }
+
+        getSender().tell(messageSupplier.get(), getSelf());
     }
 
-    private class ShardInformation {
-        private final String shardName;
-        private final ActorRef actor;
-        private final ActorPath actorPath;
-        private final Map<String, String> peerAddresses;
+    private static NoShardLeaderException createNoShardLeaderException(ShardIdentifier shardId) {
+        return new NoShardLeaderException(null, shardId.toString());
+    }
 
-        private ShardInformation(String shardName, ActorRef actor,
-            Map<String, String> peerAddresses) {
-            this.shardName = shardName;
-            this.actor = actor;
-            this.actorPath = actor.path();
-            this.peerAddresses = peerAddresses;
+    private static NotInitializedException createNotInitializedException(ShardIdentifier shardId) {
+        return new NotInitializedException(String.format(
+                "Found primary shard %s but it's not initialized yet. Please try again later", shardId));
+    }
+
+    private void memberRemoved(ClusterEvent.MemberRemoved message) {
+        String memberName = message.member().roles().head();
+
+        LOG.debug("{}: Received MemberRemoved: memberName: {}, address: {}", persistenceId(), memberName,
+                message.member().address());
+
+        peerAddressResolver.removePeerAddress(memberName);
+
+        for(ShardInformation info : localShards.values()){
+            info.peerDown(memberName, getShardIdentifier(memberName, info.getShardName()).toString(), getSelf());
         }
+    }
 
-        public String getShardName() {
-            return shardName;
+    private void memberExited(ClusterEvent.MemberExited message) {
+        String memberName = message.member().roles().head();
+
+        LOG.debug("{}: Received MemberExited: memberName: {}, address: {}", persistenceId(), memberName,
+                message.member().address());
+
+        peerAddressResolver.removePeerAddress(memberName);
+
+        for(ShardInformation info : localShards.values()){
+            info.peerDown(memberName, getShardIdentifier(memberName, info.getShardName()).toString(), getSelf());
         }
+    }
 
-        public ActorRef getActor(){
-            return actor;
+    private void memberUp(ClusterEvent.MemberUp message) {
+        String memberName = message.member().roles().head();
+
+        LOG.debug("{}: Received MemberUp: memberName: {}, address: {}", persistenceId(), memberName,
+                message.member().address());
+
+        addPeerAddress(memberName, message.member().address());
+
+        checkReady();
+    }
+
+    private void addPeerAddress(String memberName, Address address) {
+        peerAddressResolver.addPeerAddress(memberName, address);
+
+        for(ShardInformation info : localShards.values()){
+            String shardName = info.getShardName();
+            String peerId = getShardIdentifier(memberName, shardName).toString();
+            info.updatePeerAddress(peerId, peerAddressResolver.getShardActorAddress(shardName, memberName), getSelf());
+
+            info.peerUp(memberName, peerId, getSelf());
         }
+    }
 
-        public ActorPath getActorPath() {
-            return actorPath;
+    private void memberReachable(ClusterEvent.ReachableMember message) {
+        String memberName = message.member().roles().head();
+        LOG.debug("Received ReachableMember: memberName {}, address: {}", memberName, message.member().address());
+
+        addPeerAddress(memberName, message.member().address());
+
+        markMemberAvailable(memberName);
+    }
+
+    private void memberUnreachable(ClusterEvent.UnreachableMember message) {
+        String memberName = message.member().roles().head();
+        LOG.debug("Received UnreachableMember: memberName {}, address: {}", memberName, message.member().address());
+
+        markMemberUnavailable(memberName);
+    }
+
+    private void markMemberUnavailable(final String memberName) {
+        for(ShardInformation info : localShards.values()){
+            String leaderId = info.getLeaderId();
+            if(leaderId != null && leaderId.contains(memberName)) {
+                LOG.debug("Marking Leader {} as unavailable.", leaderId);
+                info.setLeaderAvailable(false);
+
+                primaryShardInfoCache.remove(info.getShardName());
+            }
+
+            info.peerDown(memberName, getShardIdentifier(memberName, info.getShardName()).toString(), getSelf());
         }
+    }
+
+    private void markMemberAvailable(final String memberName) {
+        for(ShardInformation info : localShards.values()){
+            String leaderId = info.getLeaderId();
+            if(leaderId != null && leaderId.contains(memberName)) {
+                LOG.debug("Marking Leader {} as available.", leaderId);
+                info.setLeaderAvailable(true);
+            }
 
-        public Map<String, String> getPeerAddresses() {
-            return peerAddresses;
+            info.peerUp(memberName, getShardIdentifier(memberName, info.getShardName()).toString(), getSelf());
         }
+    }
 
-        public void updatePeerAddress(String peerId, String peerAddress){
-            LOG.info("updatePeerAddress for peer {} with address {}", peerId, peerAddress);
-            if(peerAddresses.containsKey(peerId)){
-                peerAddresses.put(peerId, peerAddress);
+    private void onDatastoreContextFactory(DatastoreContextFactory factory) {
+        datastoreContextFactory = factory;
+        for (ShardInformation info : localShards.values()) {
+            info.setDatastoreContext(newShardDatastoreContext(info.getShardName()), getSelf());
+        }
+    }
+
+    private void onSwitchShardBehavior(SwitchShardBehavior message) {
+        ShardIdentifier identifier = ShardIdentifier.builder().fromShardIdString(message.getShardName()).build();
+
+        ShardInformation shardInformation = localShards.get(identifier.getShardName());
+
+        if(shardInformation != null && shardInformation.getActor() != null) {
+            shardInformation.getActor().tell(
+                    new SwitchBehavior(RaftState.valueOf(message.getNewState()), message.getTerm()), getSelf());
+        } else {
+            LOG.warn("Could not switch the behavior of shard {} to {} - shard is not yet available",
+                    message.getShardName(), message.getNewState());
+        }
+    }
 
-                LOG.info("Sending PeerAddressResolved for peer {} with address {} to {}", peerId, peerAddress, actor.path());
+    /**
+     * Notifies all the local shards of a change in the schema context
+     *
+     * @param message
+     */
+    private void updateSchemaContext(final Object message) {
+        schemaContext = ((UpdateSchemaContext) message).getSchemaContext();
 
-                actor
-                    .tell(new PeerAddressResolved(peerId, peerAddress),
-                        getSelf());
+        LOG.debug("Got updated SchemaContext: # of modules {}", schemaContext.getAllModuleIdentifiers().size());
 
+        for (ShardInformation info : localShards.values()) {
+            if (info.getActor() == null) {
+                LOG.debug("Creating Shard {}", info.getShardId());
+                info.setActor(newShardActor(schemaContext, info));
+            } else {
+                info.getActor().tell(message, getSelf());
             }
         }
     }
-}
+
+    @VisibleForTesting
+    protected ClusterWrapper getCluster() {
+        return cluster;
+    }
+
+    @VisibleForTesting
+    protected ActorRef newShardActor(final SchemaContext schemaContext, ShardInformation info) {
+        return getContext().actorOf(info.newProps(schemaContext)
+                .withDispatcher(shardDispatcherPath), info.getShardId().toString());
+    }
+
+    private void findPrimary(FindPrimary message) {
+        LOG.debug("{}: In findPrimary: {}", persistenceId(), message);
+
+        final String shardName = message.getShardName();
+        final boolean canReturnLocalShardState = !(message instanceof RemoteFindPrimary);
+
+        // First see if the there is a local replica for the shard
+        final ShardInformation info = localShards.get(shardName);
+        if (info != null && info.isActiveMember()) {
+            sendResponse(info, message.isWaitUntilReady(), true, new Supplier<Object>() {
+                @Override
+                public Object get() {
+                    String primaryPath = info.getSerializedLeaderActor();
+                    Object found = canReturnLocalShardState && info.isLeader() ?
+                            new LocalPrimaryShardFound(primaryPath, info.getLocalShardDataTree().get()) :
+                                new RemotePrimaryShardFound(primaryPath, info.getLeaderVersion());
+
+                            if(LOG.isDebugEnabled()) {
+                                LOG.debug("{}: Found primary for {}: {}", persistenceId(), shardName, found);
+                            }
+
+                            return found;
+                }
+            });
+
+            return;
+        }
+
+        Collection<String> visitedAddresses;
+        if(message instanceof RemoteFindPrimary) {
+            visitedAddresses = ((RemoteFindPrimary)message).getVisitedAddresses();
+        } else {
+            visitedAddresses = new ArrayList<>();
+        }
+
+        visitedAddresses.add(peerAddressResolver.getShardManagerActorPathBuilder(cluster.getSelfAddress()).toString());
+
+        for(String address: peerAddressResolver.getShardManagerPeerActorAddresses()) {
+            if(visitedAddresses.contains(address)) {
+                continue;
+            }
+
+            LOG.debug("{}: findPrimary for {} forwarding to remote ShardManager {}", persistenceId(),
+                    shardName, address);
+
+            getContext().actorSelection(address).forward(new RemoteFindPrimary(shardName,
+                    message.isWaitUntilReady(), visitedAddresses), getContext());
+            return;
+        }
+
+        LOG.debug("{}: No shard found for {}", persistenceId(), shardName);
+
+        getSender().tell(new PrimaryNotFoundException(
+                String.format("No primary shard found for %s.", shardName)), getSelf());
+    }
+
+    /**
+     * Construct the name of the shard actor given the name of the member on
+     * which the shard resides and the name of the shard
+     *
+     * @param memberName
+     * @param shardName
+     * @return
+     */
+    private ShardIdentifier getShardIdentifier(String memberName, String shardName){
+        return peerAddressResolver.getShardIdentifier(memberName, shardName);
+    }
+
+    /**
+     * Create shards that are local to the member on which the ShardManager
+     * runs
+     *
+     */
+    private void createLocalShards() {
+        String memberName = this.cluster.getCurrentMemberName();
+        Collection<String> memberShardNames = this.configuration.getMemberShardNames(memberName);
+
+        Map<String, DatastoreSnapshot.ShardSnapshot> shardSnapshots = new HashMap<>();
+        if(restoreFromSnapshot != null)
+        {
+            for(DatastoreSnapshot.ShardSnapshot snapshot: restoreFromSnapshot.getShardSnapshots()) {
+                shardSnapshots.put(snapshot.getName(), snapshot);
+            }
+        }
+
+        restoreFromSnapshot = null; // null out to GC
+
+        for(String shardName : memberShardNames){
+            ShardIdentifier shardId = getShardIdentifier(memberName, shardName);
+
+            LOG.debug("{}: Creating local shard: {}", persistenceId(), shardId);
+
+            Map<String, String> peerAddresses = getPeerAddresses(shardName);
+            localShards.put(shardName, new ShardInformation(shardName, shardId, peerAddresses,
+                    newShardDatastoreContext(shardName), Shard.builder().restoreFromSnapshot(
+                        shardSnapshots.get(shardName)), peerAddressResolver));
+            mBean.addLocalShard(shardId.toString());
+        }
+    }
+
+    /**
+     * Given the name of the shard find the addresses of all it's peers
+     *
+     * @param shardName
+     */
+    private Map<String, String> getPeerAddresses(String shardName) {
+        Collection<String> members = configuration.getMembersFromShardName(shardName);
+        Map<String, String> peerAddresses = new HashMap<>();
+
+        String currentMemberName = this.cluster.getCurrentMemberName();
+
+        for(String memberName : members) {
+            if(!currentMemberName.equals(memberName)) {
+                ShardIdentifier shardId = getShardIdentifier(memberName, shardName);
+                String address = peerAddressResolver.getShardActorAddress(shardName, memberName);
+                peerAddresses.put(shardId.toString(), address);
+            }
+        }
+        return peerAddresses;
+    }
+
+    @Override
+    public SupervisorStrategy supervisorStrategy() {
+
+        return new OneForOneStrategy(10, Duration.create("1 minute"),
+                new Function<Throwable, SupervisorStrategy.Directive>() {
+            @Override
+            public SupervisorStrategy.Directive apply(Throwable t) {
+                LOG.warn("Supervisor Strategy caught unexpected exception - resuming", t);
+                return SupervisorStrategy.resume();
+            }
+        }
+                );
+
+    }
+
+    @Override
+    public String persistenceId() {
+        return persistenceId;
+    }
+
+    @VisibleForTesting
+    ShardManagerInfoMBean getMBean(){
+        return mBean;
+    }
+
+    private boolean isShardReplicaOperationInProgress(final String shardName, final ActorRef sender) {
+        if (shardReplicaOperationsInProgress.contains(shardName)) {
+            String msg = String.format("A shard replica operation for %s is already in progress", shardName);
+            LOG.debug ("{}: {}", persistenceId(), msg);
+            sender.tell(new akka.actor.Status.Failure(new IllegalStateException(msg)), getSelf());
+            return true;
+        }
+
+        return false;
+    }
+
+    private void onAddShardReplica (final AddShardReplica shardReplicaMsg) {
+        final String shardName = shardReplicaMsg.getShardName();
+
+        LOG.debug("{}: onAddShardReplica: {}", persistenceId(), shardReplicaMsg);
+
+        // verify the shard with the specified name is present in the cluster configuration
+        if (!(this.configuration.isShardConfigured(shardName))) {
+            String msg = String.format("No module configuration exists for shard %s", shardName);
+            LOG.debug ("{}: {}", persistenceId(), msg);
+            getSender().tell(new akka.actor.Status.Failure(new IllegalArgumentException(msg)), getSelf());
+            return;
+        }
+
+        // Create the localShard
+        if (schemaContext == null) {
+            String msg = String.format(
+                  "No SchemaContext is available in order to create a local shard instance for %s", shardName);
+            LOG.debug ("{}: {}", persistenceId(), msg);
+            getSender().tell(new akka.actor.Status.Failure(new IllegalStateException(msg)), getSelf());
+            return;
+        }
+
+        findPrimary(shardName, new AutoFindPrimaryFailureResponseHandler(getSender(), shardName, persistenceId(), getSelf()) {
+            @Override
+            public void onRemotePrimaryShardFound(RemotePrimaryShardFound response) {
+                getSelf().tell(new PrimaryShardFoundForContext(getShardName(), shardReplicaMsg, response), getTargetActor());
+            }
+
+            @Override
+            public void onLocalPrimaryFound(LocalPrimaryShardFound message) {
+                sendLocalReplicaAlreadyExistsReply(getShardName(), getTargetActor());
+            }
+
+        });
+    }
+
+    private void sendLocalReplicaAlreadyExistsReply(String shardName, ActorRef sender) {
+        String msg = String.format("Local shard %s already exists", shardName);
+        LOG.debug ("{}: {}", persistenceId(), msg);
+        sender.tell(new akka.actor.Status.Failure(new AlreadyExistsException(msg)), getSelf());
+    }
+
+    private void addShard(final String shardName, final RemotePrimaryShardFound response, final ActorRef sender) {
+        if(isShardReplicaOperationInProgress(shardName, sender)) {
+            return;
+        }
+
+        shardReplicaOperationsInProgress.add(shardName);
+
+        final ShardInformation shardInfo;
+        final boolean removeShardOnFailure;
+        ShardInformation existingShardInfo = localShards.get(shardName);
+        if(existingShardInfo == null) {
+            removeShardOnFailure = true;
+            ShardIdentifier shardId = getShardIdentifier(cluster.getCurrentMemberName(), shardName);
+
+            DatastoreContext datastoreContext = newShardDatastoreContextBuilder(shardName).customRaftPolicyImplementation(
+                    DisableElectionsRaftPolicy.class.getName()).build();
+
+            shardInfo = new ShardInformation(shardName, shardId, getPeerAddresses(shardName), datastoreContext,
+                    Shard.builder(), peerAddressResolver);
+            shardInfo.setActiveMember(false);
+            localShards.put(shardName, shardInfo);
+            shardInfo.setActor(newShardActor(schemaContext, shardInfo));
+        } else {
+            removeShardOnFailure = false;
+            shardInfo = existingShardInfo;
+        }
+
+        String localShardAddress = peerAddressResolver.getShardActorAddress(shardName, cluster.getCurrentMemberName());
+
+        //inform ShardLeader to add this shard as a replica by sending an AddServer message
+        LOG.debug ("{}: Sending AddServer message to peer {} for shard {}", persistenceId(),
+                response.getPrimaryPath(), shardInfo.getShardId());
+
+        Timeout addServerTimeout = new Timeout(shardInfo.getDatastoreContext().getShardLeaderElectionTimeout().
+                duration());
+        Future<Object> futureObj = ask(getContext().actorSelection(response.getPrimaryPath()),
+            new AddServer(shardInfo.getShardId().toString(), localShardAddress, true), addServerTimeout);
+
+        futureObj.onComplete(new OnComplete<Object>() {
+            @Override
+            public void onComplete(Throwable failure, Object addServerResponse) {
+                if (failure != null) {
+                    LOG.debug ("{}: AddServer request to {} for {} failed", persistenceId(),
+                            response.getPrimaryPath(), shardName, failure);
+
+                    String msg = String.format("AddServer request to leader %s for shard %s failed",
+                            response.getPrimaryPath(), shardName);
+                    self().tell(new ForwardedAddServerFailure(shardName, msg, failure, removeShardOnFailure), sender);
+                } else {
+                    self().tell(new ForwardedAddServerReply(shardInfo, (AddServerReply)addServerResponse,
+                            response.getPrimaryPath(), removeShardOnFailure), sender);
+                }
+            }
+        }, new Dispatchers(context().system().dispatchers()).getDispatcher(Dispatchers.DispatcherType.Client));
+    }
+
+    private void onAddServerFailure(String shardName, String message, Throwable failure, ActorRef sender,
+            boolean removeShardOnFailure) {
+        shardReplicaOperationsInProgress.remove(shardName);
+
+        if(removeShardOnFailure) {
+            ShardInformation shardInfo = localShards.remove(shardName);
+            if (shardInfo.getActor() != null) {
+                shardInfo.getActor().tell(PoisonPill.getInstance(), getSelf());
+            }
+        }
+
+        sender.tell(new akka.actor.Status.Failure(message == null ? failure :
+            new RuntimeException(message, failure)), getSelf());
+    }
+
+    private void onAddServerReply(ShardInformation shardInfo, AddServerReply replyMsg, ActorRef sender,
+            String leaderPath, boolean removeShardOnFailure) {
+        String shardName = shardInfo.getShardName();
+        shardReplicaOperationsInProgress.remove(shardName);
+
+        LOG.debug ("{}: Received {} for shard {} from leader {}", persistenceId(), replyMsg, shardName, leaderPath);
+
+        if (replyMsg.getStatus() == ServerChangeStatus.OK) {
+            LOG.debug ("{}: Leader shard successfully added the replica shard {}", persistenceId(), shardName);
+
+            // Make the local shard voting capable
+            shardInfo.setDatastoreContext(newShardDatastoreContext(shardName), getSelf());
+            shardInfo.setActiveMember(true);
+            persistShardList();
+
+            mBean.addLocalShard(shardInfo.getShardId().toString());
+            sender.tell(new akka.actor.Status.Success(null), getSelf());
+        } else if(replyMsg.getStatus() == ServerChangeStatus.ALREADY_EXISTS) {
+            sendLocalReplicaAlreadyExistsReply(shardName, sender);
+        } else {
+            LOG.warn ("{}: Leader failed to add shard replica {} with status {}",
+                    persistenceId(), shardName, replyMsg.getStatus());
+
+            Exception failure = getServerChangeException(AddServer.class, replyMsg.getStatus(), leaderPath, shardInfo.getShardId());
+
+            onAddServerFailure(shardName, null, failure, sender, removeShardOnFailure);
+        }
+    }
+
+    private Exception getServerChangeException(Class<?> serverChange, ServerChangeStatus serverChangeStatus,
+                                               String leaderPath, ShardIdentifier shardId) {
+        Exception failure;
+        switch (serverChangeStatus) {
+            case TIMEOUT:
+                failure = new TimeoutException(String.format(
+                        "The shard leader %s timed out trying to replicate the initial data to the new shard %s." +
+                        "Possible causes - there was a problem replicating the data or shard leadership changed while replicating the shard data",
+                        leaderPath, shardId.getShardName()));
+                break;
+            case NO_LEADER:
+                failure = createNoShardLeaderException(shardId);
+                break;
+            case NOT_SUPPORTED:
+                failure = new UnsupportedOperationException(String.format("%s request is not supported for shard %s",
+                        serverChange.getSimpleName(), shardId.getShardName()));
+                break;
+            default :
+                failure = new RuntimeException(String.format(
+                        "%s request to leader %s for shard %s failed with status %s",
+                        serverChange.getSimpleName(), leaderPath, shardId.getShardName(), serverChangeStatus));
+        }
+        return failure;
+    }
+
+    private void onRemoveShardReplica (final RemoveShardReplica shardReplicaMsg) {
+        LOG.debug("{}: onRemoveShardReplica: {}", persistenceId(), shardReplicaMsg);
+
+        findPrimary(shardReplicaMsg.getShardName(), new AutoFindPrimaryFailureResponseHandler(getSender(),
+                shardReplicaMsg.getShardName(), persistenceId(), getSelf()) {
+            @Override
+            public void onRemotePrimaryShardFound(RemotePrimaryShardFound response) {
+                getSelf().tell(new PrimaryShardFoundForContext(getShardName(), shardReplicaMsg, response), getTargetActor());
+            }
+
+            @Override
+            public void onLocalPrimaryFound(LocalPrimaryShardFound response) {
+                getSelf().tell(new PrimaryShardFoundForContext(getShardName(), shardReplicaMsg, response), getTargetActor());
+            }
+        });
+    }
+
+    private void persistShardList() {
+        List<String> shardList = new ArrayList<>(localShards.keySet());
+        for (ShardInformation shardInfo : localShards.values()) {
+            if (!shardInfo.isActiveMember()) {
+                shardList.remove(shardInfo.getShardName());
+            }
+        }
+        LOG.debug ("{}: persisting the shard list {}", persistenceId(), shardList);
+        saveSnapshot(updateShardManagerSnapshot(shardList));
+    }
+
+    private ShardManagerSnapshot updateShardManagerSnapshot(List<String> shardList) {
+        currentSnapshot = new ShardManagerSnapshot(shardList);
+        return currentSnapshot;
+    }
+
+    private void applyShardManagerSnapshot(ShardManagerSnapshot snapshot) {
+        currentSnapshot = snapshot;
+
+        LOG.debug ("{}: onSnapshotOffer: {}", persistenceId(), currentSnapshot);
+
+        String currentMember = cluster.getCurrentMemberName();
+        Set<String> configuredShardList =
+            new HashSet<>(configuration.getMemberShardNames(currentMember));
+        for (String shard : currentSnapshot.getShardList()) {
+            if (!configuredShardList.contains(shard)) {
+                // add the current member as a replica for the shard
+                LOG.debug ("{}: adding shard {}", persistenceId(), shard);
+                configuration.addMemberReplicaForShard(shard, currentMember);
+            } else {
+                configuredShardList.remove(shard);
+            }
+        }
+        for (String shard : configuredShardList) {
+            // remove the member as a replica for the shard
+            LOG.debug ("{}: removing shard {}", persistenceId(), shard);
+            configuration.removeMemberReplicaForShard(shard, currentMember);
+        }
+    }
+
+    private void onSaveSnapshotSuccess (SaveSnapshotSuccess successMessage) {
+        LOG.debug ("{} saved ShardManager snapshot successfully. Deleting the prev snapshot if available",
+            persistenceId());
+        deleteSnapshots(new SnapshotSelectionCriteria(scala.Long.MaxValue(), (successMessage.metadata().timestamp() - 1)));
+    }
+
+    private static class ForwardedAddServerReply {
+        ShardInformation shardInfo;
+        AddServerReply addServerReply;
+        String leaderPath;
+        boolean removeShardOnFailure;
+
+        ForwardedAddServerReply(ShardInformation shardInfo, AddServerReply addServerReply, String leaderPath,
+                boolean removeShardOnFailure) {
+            this.shardInfo = shardInfo;
+            this.addServerReply = addServerReply;
+            this.leaderPath = leaderPath;
+            this.removeShardOnFailure = removeShardOnFailure;
+        }
+    }
+
+    private static class ForwardedAddServerFailure {
+        String shardName;
+        String failureMessage;
+        Throwable failure;
+        boolean removeShardOnFailure;
+
+        ForwardedAddServerFailure(String shardName, String failureMessage, Throwable failure,
+                boolean removeShardOnFailure) {
+            this.shardName = shardName;
+            this.failureMessage = failureMessage;
+            this.failure = failure;
+            this.removeShardOnFailure = removeShardOnFailure;
+        }
+    }
+
+    @VisibleForTesting
+    protected static class ShardInformation {
+        private final ShardIdentifier shardId;
+        private final String shardName;
+        private ActorRef actor;
+        private ActorPath actorPath;
+        private final Map<String, String> initialPeerAddresses;
+        private Optional<DataTree> localShardDataTree;
+        private boolean leaderAvailable = false;
+
+        // flag that determines if the actor is ready for business
+        private boolean actorInitialized = false;
+
+        private boolean followerSyncStatus = false;
+
+        private final Set<OnShardInitialized> onShardInitializedSet = Sets.newHashSet();
+        private String role ;
+        private String leaderId;
+        private short leaderVersion;
+
+        private DatastoreContext datastoreContext;
+        private Shard.AbstractBuilder<?, ?> builder;
+        private final ShardPeerAddressResolver addressResolver;
+        private boolean isActiveMember = true;
+
+        private ShardInformation(String shardName, ShardIdentifier shardId,
+                Map<String, String> initialPeerAddresses, DatastoreContext datastoreContext,
+                Shard.AbstractBuilder<?, ?> builder, ShardPeerAddressResolver addressResolver) {
+            this.shardName = shardName;
+            this.shardId = shardId;
+            this.initialPeerAddresses = initialPeerAddresses;
+            this.datastoreContext = datastoreContext;
+            this.builder = builder;
+            this.addressResolver = addressResolver;
+        }
+
+        Props newProps(SchemaContext schemaContext) {
+            Preconditions.checkNotNull(builder);
+            Props props = builder.id(shardId).peerAddresses(initialPeerAddresses).datastoreContext(datastoreContext).
+                    schemaContext(schemaContext).props();
+            builder = null;
+            return props;
+        }
+
+        String getShardName() {
+            return shardName;
+        }
+
+        @Nullable
+        ActorRef getActor(){
+            return actor;
+        }
+
+        ActorPath getActorPath() {
+            return actorPath;
+        }
+
+        void setActor(ActorRef actor) {
+            this.actor = actor;
+            this.actorPath = actor.path();
+        }
+
+        ShardIdentifier getShardId() {
+            return shardId;
+        }
+
+        void setLocalDataTree(Optional<DataTree> localShardDataTree) {
+            this.localShardDataTree = localShardDataTree;
+        }
+
+        Optional<DataTree> getLocalShardDataTree() {
+            return localShardDataTree;
+        }
+
+        DatastoreContext getDatastoreContext() {
+            return datastoreContext;
+        }
+
+        void setDatastoreContext(DatastoreContext datastoreContext, ActorRef sender) {
+            this.datastoreContext = datastoreContext;
+            if (actor != null) {
+                LOG.debug ("Sending new DatastoreContext to {}", shardId);
+                actor.tell(this.datastoreContext, sender);
+            }
+        }
+
+        void updatePeerAddress(String peerId, String peerAddress, ActorRef sender){
+            LOG.info("updatePeerAddress for peer {} with address {}", peerId, peerAddress);
+
+            if(actor != null) {
+                if(LOG.isDebugEnabled()) {
+                    LOG.debug("Sending PeerAddressResolved for peer {} with address {} to {}",
+                            peerId, peerAddress, actor.path());
+                }
+
+                actor.tell(new PeerAddressResolved(peerId, peerAddress), sender);
+            }
+
+            notifyOnShardInitializedCallbacks();
+        }
+
+        void peerDown(String memberName, String peerId, ActorRef sender) {
+            if(actor != null) {
+                actor.tell(new PeerDown(memberName, peerId), sender);
+            }
+        }
+
+        void peerUp(String memberName, String peerId, ActorRef sender) {
+            if(actor != null) {
+                actor.tell(new PeerUp(memberName, peerId), sender);
+            }
+        }
+
+        boolean isShardReady() {
+            return !RaftState.Candidate.name().equals(role) && !Strings.isNullOrEmpty(role);
+        }
+
+        boolean isShardReadyWithLeaderId() {
+            return leaderAvailable && isShardReady() && !RaftState.IsolatedLeader.name().equals(role) &&
+                    (isLeader() || addressResolver.resolve(leaderId) != null);
+        }
+
+        boolean isShardInitialized() {
+            return getActor() != null && actorInitialized;
+        }
+
+        boolean isLeader() {
+            return Objects.equal(leaderId, shardId.toString());
+        }
+
+        String getSerializedLeaderActor() {
+            if(isLeader()) {
+                return Serialization.serializedActorPath(getActor());
+            } else {
+                return addressResolver.resolve(leaderId);
+            }
+        }
+
+        void setActorInitialized() {
+            LOG.debug("Shard {} is initialized", shardId);
+
+            this.actorInitialized = true;
+
+            notifyOnShardInitializedCallbacks();
+        }
+
+        private void notifyOnShardInitializedCallbacks() {
+            if(onShardInitializedSet.isEmpty()) {
+                return;
+            }
+
+            boolean ready = isShardReadyWithLeaderId();
+
+            if(LOG.isDebugEnabled()) {
+                LOG.debug("Shard {} is {} - notifying {} OnShardInitialized callbacks", shardId,
+                        ready ? "ready" : "initialized", onShardInitializedSet.size());
+            }
+
+            Iterator<OnShardInitialized> iter = onShardInitializedSet.iterator();
+            while(iter.hasNext()) {
+                OnShardInitialized onShardInitialized = iter.next();
+                if(!(onShardInitialized instanceof OnShardReady) || ready) {
+                    iter.remove();
+                    onShardInitialized.getTimeoutSchedule().cancel();
+                    onShardInitialized.getReplyRunnable().run();
+                }
+            }
+        }
+
+        void addOnShardInitialized(OnShardInitialized onShardInitialized) {
+            onShardInitializedSet.add(onShardInitialized);
+        }
+
+        void removeOnShardInitialized(OnShardInitialized onShardInitialized) {
+            onShardInitializedSet.remove(onShardInitialized);
+        }
+
+        void setRole(String newRole) {
+            this.role = newRole;
+
+            notifyOnShardInitializedCallbacks();
+        }
+
+        void setFollowerSyncStatus(boolean syncStatus){
+            this.followerSyncStatus = syncStatus;
+        }
+
+        boolean isInSync(){
+            if(RaftState.Follower.name().equals(this.role)){
+                return followerSyncStatus;
+            } else if(RaftState.Leader.name().equals(this.role)){
+                return true;
+            }
+
+            return false;
+        }
+
+        boolean setLeaderId(String leaderId) {
+            boolean changed = !Objects.equal(this.leaderId, leaderId);
+            this.leaderId = leaderId;
+            if(leaderId != null) {
+                this.leaderAvailable = true;
+            }
+            notifyOnShardInitializedCallbacks();
+
+            return changed;
+        }
+
+        String getLeaderId() {
+            return leaderId;
+        }
+
+        void setLeaderAvailable(boolean leaderAvailable) {
+            this.leaderAvailable = leaderAvailable;
+
+            if(leaderAvailable) {
+                notifyOnShardInitializedCallbacks();
+            }
+        }
+
+        short getLeaderVersion() {
+            return leaderVersion;
+        }
+
+        void setLeaderVersion(short leaderVersion) {
+            this.leaderVersion = leaderVersion;
+        }
+
+        boolean isActiveMember() {
+            return isActiveMember;
+        }
+
+        void setActiveMember(boolean isActiveMember) {
+            this.isActiveMember = isActiveMember;
+        }
+    }
+
+    private static class OnShardInitialized {
+        private final Runnable replyRunnable;
+        private Cancellable timeoutSchedule;
+
+        OnShardInitialized(Runnable replyRunnable) {
+            this.replyRunnable = replyRunnable;
+        }
+
+        Runnable getReplyRunnable() {
+            return replyRunnable;
+        }
+
+        Cancellable getTimeoutSchedule() {
+            return timeoutSchedule;
+        }
+
+        void setTimeoutSchedule(Cancellable timeoutSchedule) {
+            this.timeoutSchedule = timeoutSchedule;
+        }
+    }
+
+    private static class OnShardReady extends OnShardInitialized {
+        OnShardReady(Runnable replyRunnable) {
+            super(replyRunnable);
+        }
+    }
+
+    private static class ShardNotInitializedTimeout {
+        private final ActorRef sender;
+        private final ShardInformation shardInfo;
+        private final OnShardInitialized onShardInitialized;
+
+        ShardNotInitializedTimeout(ShardInformation shardInfo, OnShardInitialized onShardInitialized, ActorRef sender) {
+            this.sender = sender;
+            this.shardInfo = shardInfo;
+            this.onShardInitialized = onShardInitialized;
+        }
+
+        ActorRef getSender() {
+            return sender;
+        }
+
+        ShardInformation getShardInfo() {
+            return shardInfo;
+        }
+
+        OnShardInitialized getOnShardInitialized() {
+            return onShardInitialized;
+        }
+    }
+
+    /**
+     * We no longer persist SchemaContextModules but keep this class around for now for backwards
+     * compatibility so we don't get de-serialization failures on upgrade from Helium.
+     */
+    @Deprecated
+    static class SchemaContextModules implements Serializable {
+        private static final long serialVersionUID = -8884620101025936590L;
+
+        private final Set<String> modules;
+
+        SchemaContextModules(Set<String> modules){
+            this.modules = modules;
+        }
+
+        public Set<String> getModules() {
+            return modules;
+        }
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public static abstract class AbstractBuilder<T extends AbstractBuilder<T>> {
+        private ClusterWrapper cluster;
+        private Configuration configuration;
+        private DatastoreContextFactory datastoreContextFactory;
+        private CountDownLatch waitTillReadyCountdownLatch;
+        private PrimaryShardInfoFutureCache primaryShardInfoCache;
+        private DatastoreSnapshot restoreFromSnapshot;
+
+        private volatile boolean sealed;
+
+        @SuppressWarnings("unchecked")
+        private T self() {
+            return (T) this;
+        }
+
+        protected void checkSealed() {
+            Preconditions.checkState(!sealed, "Builder is already sealed - further modifications are not allowed");
+        }
+
+        public T cluster(ClusterWrapper cluster) {
+            checkSealed();
+            this.cluster = cluster;
+            return self();
+        }
+
+        public T configuration(Configuration configuration) {
+            checkSealed();
+            this.configuration = configuration;
+            return self();
+        }
+
+        public T datastoreContextFactory(DatastoreContextFactory datastoreContextFactory) {
+            checkSealed();
+            this.datastoreContextFactory = datastoreContextFactory;
+            return self();
+        }
+
+        public T waitTillReadyCountdownLatch(CountDownLatch waitTillReadyCountdownLatch) {
+            checkSealed();
+            this.waitTillReadyCountdownLatch = waitTillReadyCountdownLatch;
+            return self();
+        }
+
+        public T primaryShardInfoCache(PrimaryShardInfoFutureCache primaryShardInfoCache) {
+            checkSealed();
+            this.primaryShardInfoCache = primaryShardInfoCache;
+            return self();
+        }
+
+        public T restoreFromSnapshot(DatastoreSnapshot restoreFromSnapshot) {
+            checkSealed();
+            this.restoreFromSnapshot = restoreFromSnapshot;
+            return self();
+        }
+
+        protected void verify() {
+            sealed = true;
+            Preconditions.checkNotNull(cluster, "cluster should not be null");
+            Preconditions.checkNotNull(configuration, "configuration should not be null");
+            Preconditions.checkNotNull(datastoreContextFactory, "datastoreContextFactory should not be null");
+            Preconditions.checkNotNull(waitTillReadyCountdownLatch, "waitTillReadyCountdownLatch should not be null");
+            Preconditions.checkNotNull(primaryShardInfoCache, "primaryShardInfoCache should not be null");
+        }
+
+        public Props props() {
+            verify();
+            return Props.create(ShardManager.class, this);
+        }
+    }
+
+    public static class Builder extends AbstractBuilder<Builder> {
+    }
+
+    private void findPrimary(final String shardName, final FindPrimaryResponseHandler handler) {
+        Timeout findPrimaryTimeout = new Timeout(datastoreContextFactory.getBaseDatastoreContext().
+                getShardInitializationTimeout().duration().$times(2));
+
+
+        Future<Object> futureObj = ask(getSelf(), new FindPrimary(shardName, true), findPrimaryTimeout);
+        futureObj.onComplete(new OnComplete<Object>() {
+            @Override
+            public void onComplete(Throwable failure, Object response) {
+                if (failure != null) {
+                    handler.onFailure(failure);
+                } else {
+                    if(response instanceof RemotePrimaryShardFound) {
+                        handler.onRemotePrimaryShardFound((RemotePrimaryShardFound) response);
+                    } else if(response instanceof LocalPrimaryShardFound) {
+                        handler.onLocalPrimaryFound((LocalPrimaryShardFound) response);
+                    } else {
+                        handler.onUnknownResponse(response);
+                    }
+                }
+            }
+        }, new Dispatchers(context().system().dispatchers()).getDispatcher(Dispatchers.DispatcherType.Client));
+    }
+
+    /**
+     * The FindPrimaryResponseHandler provides specific callback methods which are invoked when a response to the
+     * a remote or local find primary message is processed
+     */
+    private static interface FindPrimaryResponseHandler {
+        /**
+         * Invoked when a Failure message is received as a response
+         *
+         * @param failure
+         */
+        void onFailure(Throwable failure);
+
+        /**
+         * Invoked when a RemotePrimaryShardFound response is received
+         *
+         * @param response
+         */
+        void onRemotePrimaryShardFound(RemotePrimaryShardFound response);
+
+        /**
+         * Invoked when a LocalPrimaryShardFound response is received
+         * @param response
+         */
+        void onLocalPrimaryFound(LocalPrimaryShardFound response);
+
+        /**
+         * Invoked when an unknown response is received. This is another type of failure.
+         *
+         * @param response
+         */
+        void onUnknownResponse(Object response);
+    }
+
+    /**
+     * The AutoFindPrimaryFailureResponseHandler automatically processes Failure responses when finding a primary
+     * replica and sends a wrapped Failure response to some targetActor
+     */
+    private static abstract class AutoFindPrimaryFailureResponseHandler implements FindPrimaryResponseHandler {
+        private final ActorRef targetActor;
+        private final String shardName;
+        private final String persistenceId;
+        private final ActorRef shardManagerActor;
+
+        /**
+         * @param targetActor The actor to whom the Failure response should be sent when a FindPrimary failure occurs
+         * @param shardName The name of the shard for which the primary replica had to be found
+         * @param persistenceId The persistenceId for the ShardManager
+         * @param shardManagerActor The ShardManager actor which triggered the call to FindPrimary
+         */
+        protected AutoFindPrimaryFailureResponseHandler(ActorRef targetActor, String shardName, String persistenceId, ActorRef shardManagerActor){
+            this.targetActor = Preconditions.checkNotNull(targetActor);
+            this.shardName = Preconditions.checkNotNull(shardName);
+            this.persistenceId = Preconditions.checkNotNull(persistenceId);
+            this.shardManagerActor = Preconditions.checkNotNull(shardManagerActor);
+        }
+
+        public ActorRef getTargetActor() {
+            return targetActor;
+        }
+
+        public String getShardName() {
+            return shardName;
+        }
+
+        @Override
+        public void onFailure(Throwable failure) {
+            LOG.debug ("{}: Received failure from FindPrimary for shard {}", persistenceId, shardName, failure);
+            targetActor.tell(new akka.actor.Status.Failure(new RuntimeException(
+                    String.format("Failed to find leader for shard %s", shardName), failure)), shardManagerActor);
+        }
+
+        @Override
+        public void onUnknownResponse(Object response) {
+            String msg = String.format("Failed to find leader for shard %s: received response: %s",
+                    shardName, response);
+            LOG.debug ("{}: {}", persistenceId, msg);
+            targetActor.tell(new akka.actor.Status.Failure(response instanceof Throwable ? (Throwable) response :
+                    new RuntimeException(msg)), shardManagerActor);
+        }
+    }
+
+
+    /**
+     * The PrimaryShardFoundForContext is a DTO which puts together a message (aka 'Context' message) which needs to be
+     * forwarded to the primary replica of a shard and the message (aka 'PrimaryShardFound' message) that is received
+     * as a successful response to find primary.
+     */
+    private static class PrimaryShardFoundForContext {
+        private final String shardName;
+        private final Object contextMessage;
+        private final RemotePrimaryShardFound remotePrimaryShardFound;
+        private final LocalPrimaryShardFound localPrimaryShardFound;
+
+        public PrimaryShardFoundForContext(@Nonnull String shardName, @Nonnull Object contextMessage,
+                @Nonnull Object primaryFoundMessage) {
+            this.shardName = Preconditions.checkNotNull(shardName);
+            this.contextMessage = Preconditions.checkNotNull(contextMessage);
+            Preconditions.checkNotNull(primaryFoundMessage);
+            this.remotePrimaryShardFound = (primaryFoundMessage instanceof RemotePrimaryShardFound) ?
+                    (RemotePrimaryShardFound) primaryFoundMessage : null;
+            this.localPrimaryShardFound = (primaryFoundMessage instanceof LocalPrimaryShardFound) ?
+                    (LocalPrimaryShardFound) primaryFoundMessage : null;
+        }
+
+        @Nonnull
+        String getPrimaryPath(){
+            if(remotePrimaryShardFound != null) {
+                return remotePrimaryShardFound.getPrimaryPath();
+            }
+            return localPrimaryShardFound.getPrimaryPath();
+        }
+
+        @Nonnull
+        Object getContextMessage() {
+            return contextMessage;
+        }
+
+        @Nullable
+        RemotePrimaryShardFound getRemotePrimaryShardFound() {
+            return remotePrimaryShardFound;
+        }
+
+        @Nonnull
+        String getShardName() {
+            return shardName;
+        }
+    }
+
+    /**
+     * The WrappedShardResponse class wraps a response from a Shard.
+     */
+    private static class WrappedShardResponse {
+        private final String shardName;
+        private final Object response;
+
+        private WrappedShardResponse(String shardName, Object response) {
+            this.shardName = shardName;
+            this.response = response;
+        }
+
+        String getShardName() {
+            return shardName;
+        }
+
+        Object getResponse() {
+            return response;
+        }
+    }
+}
+
+
+