initial sketch of ReplicaInfoService.

Change-Id: I364b023aa6be69cabb184b92fd7a0dadd5215ec9

+package org.onlab.onos.store.flow;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.Collection;
+import java.util.Collections;
+
+import org.onlab.onos.cluster.NodeId;
+
+import com.google.common.base.Optional;
+
+/**
+ * Class to represent placement information about Master/Backup copy.
+ */
+public final class ReplicaInfo {
+
+    private final Optional<NodeId> master;
+    private final Collection<NodeId> backups;
+
+    /**
+     * Creates a ReplicaInfo instance.
+     *
+     * @param master NodeId of the node where the master copy should be
+     * @param backups collection of NodeId, where backup copies should be placed
+     */
+    public ReplicaInfo(NodeId master, Collection<NodeId> backups) {
+        this.master = Optional.fromNullable(master);
+        this.backups = checkNotNull(backups);
+    }
+
+    /**
+     * Returns the NodeId, if there is a Node where the master copy should be.
+     *
+     * @return NodeId, where the master copy should be placed
+     */
+    public Optional<NodeId> master() {
+        return master;
+    }
+
+    /**
+     * Returns the collection of NodeId, where backup copies should be placed.
+     *
+     * @return collection of NodeId, where backup copies should be placed
+     */
+    public Collection<NodeId> backups() {
+        return backups;
+    }
+
+    // for Serializer
+    private ReplicaInfo() {
+        this.master = Optional.absent();
+        this.backups = Collections.emptyList();
+    }
+}

+package org.onlab.onos.store.flow;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import org.onlab.onos.event.AbstractEvent;
+import org.onlab.onos.net.DeviceId;
+
+/**
+ * Describes a device replicainfo event.
+ */
+public class ReplicaInfoEvent extends AbstractEvent<ReplicaInfoEvent.Type, DeviceId> {
+
+    private final ReplicaInfo replicaInfo;
+
+    /**
+     * Types of Replica info event.
+     */
+    public enum Type {
+        /**
+         * Event to notify that master placement should be changed.
+         */
+        MASTER_CHANGED,
+        //
+        // BACKUPS_CHANGED?
+    }
+
+
+    /**
+     * Creates an event of a given type and for the specified device,
+     * and replica info.
+     *
+     * @param type        replicainfo event type
+     * @param device      event device subject
+     * @param replicaInfo replicainfo
+     */
+    public ReplicaInfoEvent(Type type, DeviceId device, ReplicaInfo replicaInfo) {
+        super(type, device);
+        this.replicaInfo = checkNotNull(replicaInfo);
+    }
+
+    /**
+     * Returns the current replica information for the subject.
+     *
+     * @return replica information for the subject
+     */
+    public ReplicaInfo replicaInfo() {
+        return replicaInfo;
+    };
+}

+package org.onlab.onos.store.flow;
+
+import org.onlab.onos.event.EventListener;
+
+/**
+ * Entity capable of receiving Replica placement information-related events.
+ */
+public interface ReplicaInfoEventListener extends EventListener<ReplicaInfoEvent> {
+
+}
+

+package org.onlab.onos.store.flow;
+
+import org.onlab.onos.net.DeviceId;
+
+/**
+ * Service to return where the Replica should be placed.
+ */
+public interface ReplicaInfoService {
+
+    // returns where it should be.
+    /**
+     * Returns the placement information for given Device.
+     *
+     * @param deviceId identifier of the device
+     * @return placement information
+     */
+    ReplicaInfo getReplicaInfoFor(DeviceId deviceId);
+}

+package org.onlab.onos.store.flow.impl;
+
+import static org.slf4j.LoggerFactory.getLogger;
+import static org.onlab.onos.store.flow.ReplicaInfoEvent.Type.MASTER_CHANGED;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.apache.felix.scr.annotations.Service;
+import org.onlab.onos.cluster.NodeId;
+import org.onlab.onos.event.AbstractListenerRegistry;
+import org.onlab.onos.event.EventDeliveryService;
+import org.onlab.onos.mastership.MastershipEvent;
+import org.onlab.onos.mastership.MastershipListener;
+import org.onlab.onos.mastership.MastershipService;
+import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.store.flow.ReplicaInfo;
+import org.onlab.onos.store.flow.ReplicaInfoEvent;
+import org.onlab.onos.store.flow.ReplicaInfoEventListener;
+import org.onlab.onos.store.flow.ReplicaInfoService;
+import org.slf4j.Logger;
+
+/**
+ * Manages replica placement information.
+ */
+@Component(immediate = true)
+@Service
+public class ReplicaInfoManager implements ReplicaInfoService {
+
+    private final Logger log = getLogger(getClass());
+
+    private final MastershipListener mastershipListener = new InternalMastershipListener();
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected EventDeliveryService eventDispatcher;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected MastershipService mastershipService;
+
+    protected final AbstractListenerRegistry<ReplicaInfoEvent, ReplicaInfoEventListener>
+        listenerRegistry = new AbstractListenerRegistry<>();
+
+    @Activate
+    public void activate() {
+        eventDispatcher.addSink(ReplicaInfoEvent.class, listenerRegistry);
+        mastershipService.addListener(mastershipListener);
+        log.info("Started");
+    }
+
+    @Deactivate
+    public void deactivate() {
+        eventDispatcher.removeSink(ReplicaInfoEvent.class);
+        mastershipService.removeListener(mastershipListener);
+        log.info("Stopped");
+    }
+
+    @Override
+    public ReplicaInfo getReplicaInfoFor(DeviceId deviceId) {
+        // TODO: populate backup List when we reach the point we need them.
+        return new ReplicaInfo(mastershipService.getMasterFor(deviceId),
+                               Collections.<NodeId>emptyList());
+    }
+
+    final class InternalMastershipListener implements MastershipListener {
+
+        @Override
+        public void event(MastershipEvent event) {
+            // TODO: distinguish stby list update, when MastershipService,
+            //       start publishing them
+            final List<NodeId> standbyList = Collections.<NodeId>emptyList();
+            eventDispatcher.post(new ReplicaInfoEvent(MASTER_CHANGED,
+                                event.subject(),
+                                new ReplicaInfo(event.master(), standbyList)));
+        }
+    }
+
+}

@@ -2,4 +2,4 @@
  * Implementation of the distributed flow rule store using p2p synchronization
  * protocol.
  */
-package org.onlab.onos.store.flow.impl;
\ No newline at end of file
+package org.onlab.onos.store.flow.impl;