Synchronize Multimap access.

- ONOS-2626

Change-Id: I730b310e67ab858999a16565b05c2904d9d9481c

@@ -68,7 +68,6 @@ import org.onosproject.store.service.StorageService;
 import org.slf4j.Logger;
 import org.slf4j.Logger;
 
 
 import com.google.common.collect.HashMultimap;
 import com.google.common.collect.HashMultimap;
-import com.google.common.collect.ImmutableMultimap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Multimaps;
 import com.google.common.collect.Multimaps;
 import com.google.common.collect.SetMultimap;
 import com.google.common.collect.SetMultimap;
@@ -258,18 +257,24 @@ public class ECHostStore
 
 
     @Override
     @Override
     public Set<Host> getConnectedHosts(ConnectPoint connectPoint) {
     public Set<Host> getConnectedHosts(ConnectPoint connectPoint) {
+        synchronized (locations) {
             return ImmutableSet.copyOf(locations.get(connectPoint));
             return ImmutableSet.copyOf(locations.get(connectPoint));
         }
         }
+    }
 
 
     @Override
     @Override
     public Set<Host> getConnectedHosts(DeviceId deviceId) {
     public Set<Host> getConnectedHosts(DeviceId deviceId) {
-        return ImmutableMultimap.copyOf(locations)
+        Set<Host> filtered;
+        synchronized (locations) {
+            filtered = locations
                     .entries()
                     .entries()
                     .stream()
                     .stream()
                     .filter(entry -> entry.getKey().deviceId().equals(deviceId))
                     .filter(entry -> entry.getKey().deviceId().equals(deviceId))
                     .map(entry -> entry.getValue())
                     .map(entry -> entry.getValue())
                     .collect(Collectors.toSet());
                     .collect(Collectors.toSet());
         }
         }
+        return ImmutableSet.copyOf(filtered);
+    }
 
 
     private Set<Host> filter(Collection<DefaultHost> collection, Predicate<DefaultHost> predicate) {
     private Set<Host> filter(Collection<DefaultHost> collection, Predicate<DefaultHost> predicate) {
         return collection.stream().filter(predicate).collect(Collectors.toSet());
         return collection.stream().filter(predicate).collect(Collectors.toSet());