+package org.opendaylight.controller.cluster.datastore;
+
+import akka.actor.Address;
+import akka.actor.UntypedActor;
+import akka.event.Logging;
+import akka.event.LoggingAdapter;
+import org.opendaylight.controller.cluster.datastore.messages.FindPrimary;
+import org.opendaylight.controller.cluster.datastore.messages.PrimaryNotFound;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * The ShardManager has the following jobs,
+ *
+ * - Create all the local shard replicas that belong on this cluster member
+ * - Find the primary replica for any given shard
+ * - Engage in shard replica elections which decide which replica should be the primary
+ *
+ * Creation of Shard replicas
+ * ==========================
+ * When the ShardManager is constructed it reads the cluster configuration to find out which shard replicas
+ * belong on this member. It finds out the name of the current cluster member from the Akka Clustering Service.
+ *
+ * Replica Elections
+ * =================
+ * The Shard Manager uses multiple cues to initiate election.
+ * - When a member of the cluster dies
+ * - When a local shard replica dies
+ * - When a local shard replica comes alive
+ */
+public class ShardManager extends UntypedActor {
+
+ // Stores a mapping between a shard name and the address of the current primary
+ private final Map<String, Address> shardNameToPrimaryAddress = new HashMap<>();
+
+ // Stores a mapping between a member name and the address of the member
+ private final Map<String, Address> memberNameToAddress = new HashMap<>();
+
+ // Stores a mapping between the shard name and all the members on which a replica of that shard are available
+ private final Map<String, List<String>> shardNameToMembers = new HashMap<>();
+
+ LoggingAdapter log = Logging.getLogger(getContext().system(), this);
+
+ @Override
+ public void onReceive(Object message) throws Exception {
+ if(message instanceof FindPrimary ){
+ FindPrimary msg = ((FindPrimary) message);
+ getSender().tell(new PrimaryNotFound(msg.getShardName()), getSelf());
+ }
+ }
+}