Renamed AbstractListenerRegistry to ListenerRegistry (since it is not abstract).

- added checkForNonRegistrant() predicate and augmented unit tests.

Change-Id: I7ecc618f01fdc4cead6f143a1e5e0ddd03268efc

@@ -28,15 +28,20 @@ import static org.slf4j.LoggerFactory.getLogger;
  * Base implementation of an event sink and a registry capable of tracking
  * listeners and dispatching events to them as part of event sink processing.
  */
-public class AbstractListenerRegistry<E extends Event, L extends EventListener<E>>
+public class ListenerRegistry<E extends Event, L extends EventListener<E>>
         implements EventSink<E> {
 
     private final Logger log = getLogger(getClass());
 
-    protected final Set<L> listeners = new CopyOnWriteArraySet<>();
     private volatile boolean shutdown = false;
 
     /**
+     * Set of listeners that have registered.
+     */
+    protected final Set<L> listeners = new CopyOnWriteArraySet<>();
+
+
+    /**
      * Adds the specified listener.
      *
      * @param listener listener to be added
@@ -53,7 +58,9 @@ public class AbstractListenerRegistry<E extends Event, L extends EventListener<E
      */
     public void removeListener(L listener) {
         checkNotNull(listener, "Listener cannot be null");
-        checkArgument(listeners.remove(listener), "Listener not registered");
+        if (checkForNonRegistrant()) {
+            checkArgument(listeners.remove(listener), "Listener not registered");
+        }
     }
 
     @Override
@@ -68,6 +75,19 @@ public class AbstractListenerRegistry<E extends Event, L extends EventListener<E
     }
 
     /**
+     * Predicate indicating whether we should throw an exception if the
+     * argument to {@link #removeListener} is not in the current set of
+     * listeners.
+     * <p>
+     * This default implementation returns <code>true</code>.
+     *
+     * @return true if non-listed listeners should cause exception on remove
+     */
+    protected boolean checkForNonRegistrant() {
+        return true;
+    }
+
+    /**
      * Reports a problem encountered while processing an event.
      *
      * @param event event being processed
@@ -92,5 +112,4 @@ public class AbstractListenerRegistry<E extends Event, L extends EventListener<E
     public void deactivate() {
         shutdown = true;
     }
-
 }

@@ -15,50 +15,79 @@
  */
 package org.onosproject.event;
 
+import org.junit.Before;
 import org.junit.Test;
 
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 /**
- * Tests of the base listener manager.
+ * Unit tests for {@link ListenerRegistry}.
  */
-public class AbstractListenerRegistryTest {
+public class ListenerRegistryTest {
+
+    private static class RelaxedRegistry extends TestListenerRegistry {
+        @Override
+        protected boolean checkForNonRegistrant() {
+            return false;
+        }
+    }
+
+    private static final TestEvent FOO_EVENT =
+            new TestEvent(TestEvent.Type.FOO, "foo");
+    private static final TestEvent BAR_EVENT =
+            new TestEvent(TestEvent.Type.BAR, "bar");
+
+    private TestListener listener;
+    private TestListener secondListener;
+    private TestListenerRegistry manager;
+
+    @Before
+    public void setUp() {
+        listener = new TestListener();
+        secondListener = new TestListener();
+        manager = new TestListenerRegistry();
+    }
 
     @Test
     public void basics() {
-        TestListener listener = new TestListener();
-        TestListener secondListener = new TestListener();
-        TestListenerRegistry manager = new TestListenerRegistry();
         manager.addListener(listener);
         manager.addListener(secondListener);
 
-        TestEvent event = new TestEvent(TestEvent.Type.BAR, "bar");
-        manager.process(event);
-        assertTrue("event not processed", listener.events.contains(event));
-        assertTrue("event not processed", secondListener.events.contains(event));
+        manager.process(BAR_EVENT);
+        assertTrue("BAR not processed", listener.events.contains(BAR_EVENT));
+        assertTrue("BAR not processed", secondListener.events.contains(BAR_EVENT));
 
         manager.removeListener(listener);
 
-        TestEvent another = new TestEvent(TestEvent.Type.FOO, "foo");
-        manager.process(another);
-        assertFalse("event processed", listener.events.contains(another));
-        assertTrue("event not processed", secondListener.events.contains(event));
+        manager.process(FOO_EVENT);
+        assertFalse("FOO processed", listener.events.contains(FOO_EVENT));
+        assertTrue("FOO not processed", secondListener.events.contains(FOO_EVENT));
     }
 
     @Test
     public void badListener() {
-        TestListener listener = new BrokenListener();
-        TestListener secondListener = new TestListener();
-        TestListenerRegistry manager = new TestListenerRegistry();
+        listener = new BrokenListener();
+
         manager.addListener(listener);
         manager.addListener(secondListener);
 
-        TestEvent event = new TestEvent(TestEvent.Type.BAR, "bar");
-        manager.process(event);
-        assertFalse("event processed", listener.events.contains(event));
+        manager.process(BAR_EVENT);
+        assertFalse("BAR processed", listener.events.contains(BAR_EVENT));
         assertFalse("error not reported", manager.errors.isEmpty());
-        assertTrue("event not processed", secondListener.events.contains(event));
+        assertTrue("BAR not processed", secondListener.events.contains(BAR_EVENT));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void removeNonListenerCausesException() {
+        manager.removeListener(listener);
+    }
+
+    @Test
+    public void removeNonListenerIgnored() {
+        manager = new RelaxedRegistry();
+        manager.removeListener(listener);
+        assertTrue("what?", manager.listeners.isEmpty());
     }
 
 }

@@ -22,7 +22,7 @@ import java.util.List;
  * Test event listener manager fixture.
  */
 public class TestListenerRegistry
-        extends AbstractListenerRegistry<TestEvent, TestListener> {
+        extends ListenerRegistry<TestEvent, TestListener> {
 
     public final List<Throwable> errors = new ArrayList<>();
 

@@ -33,7 +33,7 @@ import org.onosproject.app.ApplicationStoreDelegate;
 import org.onosproject.core.Application;
 import org.onosproject.core.ApplicationId;
 import org.onosproject.core.Permission;
-import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
 import org.slf4j.Logger;
 
@@ -55,8 +55,8 @@ public class ApplicationManager implements ApplicationService, ApplicationAdminS
 
     private static final String APP_ID_NULL = "Application ID cannot be null";
 
-    protected final AbstractListenerRegistry<ApplicationEvent, ApplicationListener>
-            listenerRegistry = new AbstractListenerRegistry<>();
+    protected final ListenerRegistry<ApplicationEvent, ApplicationListener>
+            listenerRegistry = new ListenerRegistry<>();
 
     private final ApplicationStoreDelegate delegate = new InternalStoreDelegate();
 

@@ -32,7 +32,7 @@ import org.onosproject.cluster.ClusterStore;
 import org.onosproject.cluster.ClusterStoreDelegate;
 import org.onosproject.cluster.ControllerNode;
 import org.onosproject.cluster.NodeId;
-import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
 import org.slf4j.Logger;
 
@@ -54,8 +54,8 @@ public class ClusterManager implements ClusterService, ClusterAdminService {
 
     private ClusterStoreDelegate delegate = new InternalStoreDelegate();
 
-    protected final AbstractListenerRegistry<ClusterEvent, ClusterEventListener>
-            listenerRegistry = new AbstractListenerRegistry<>();
+    protected final ListenerRegistry<ClusterEvent, ClusterEventListener>
+            listenerRegistry = new ListenerRegistry<>();
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected ClusterStore store;

@@ -30,7 +30,7 @@ import org.onosproject.cluster.ControllerNode;
 import org.onosproject.cluster.NodeId;
 import org.onosproject.cluster.RoleInfo;
 import org.onosproject.core.MetricsHelper;
-import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
 import org.onosproject.mastership.MastershipAdminService;
 import org.onosproject.mastership.MastershipEvent;
@@ -73,8 +73,8 @@ public class MastershipManager
 
     private final Logger log = getLogger(getClass());
 
-    protected final AbstractListenerRegistry<MastershipEvent, MastershipListener>
-    listenerRegistry = new AbstractListenerRegistry<>();
+    protected final ListenerRegistry<MastershipEvent, MastershipListener>
+    listenerRegistry = new ListenerRegistry<>();
 
     private final MastershipStoreDelegate delegate = new InternalDelegate();
 

@@ -24,7 +24,7 @@ import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.apache.felix.scr.annotations.Service;
 import org.onosproject.cluster.ClusterService;
 import org.onosproject.cluster.NodeId;
-import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
 import org.onosproject.mastership.MastershipEvent;
 import org.onosproject.mastership.MastershipListener;
@@ -83,8 +83,8 @@ public class DeviceManager
 
     private final Logger log = getLogger(getClass());
 
-    protected final AbstractListenerRegistry<DeviceEvent, DeviceListener> listenerRegistry =
-            new AbstractListenerRegistry<>();
+    protected final ListenerRegistry<DeviceEvent, DeviceListener> listenerRegistry =
+            new ListenerRegistry<>();
 
     private final DeviceStoreDelegate delegate = new InternalStoreDelegate();
 

@@ -35,7 +35,7 @@ import org.onosproject.cfg.ComponentConfigService;
 import org.onosproject.core.ApplicationId;
 import org.onosproject.core.CoreService;
 import org.onosproject.core.IdGenerator;
-import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
 import org.onosproject.net.Device;
 import org.onosproject.net.DeviceId;
@@ -97,8 +97,8 @@ public class FlowRuleManager
 
     private final Logger log = getLogger(getClass());
 
-    private final AbstractListenerRegistry<FlowRuleEvent, FlowRuleListener>
-            listenerRegistry = new AbstractListenerRegistry<>();
+    private final ListenerRegistry<FlowRuleEvent, FlowRuleListener>
+            listenerRegistry = new ListenerRegistry<>();
 
     private final FlowRuleStoreDelegate delegate = new InternalStoreDelegate();
 

@@ -15,13 +15,7 @@
  */
 package org.onosproject.net.group.impl;
 
-import static org.slf4j.LoggerFactory.getLogger;
-
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Iterator;
-import java.util.Set;
-
+import com.google.common.collect.Sets;
 import org.apache.felix.scr.annotations.Activate;
 import org.apache.felix.scr.annotations.Component;
 import org.apache.felix.scr.annotations.Deactivate;
@@ -29,8 +23,8 @@ import org.apache.felix.scr.annotations.Reference;
 import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.apache.felix.scr.annotations.Service;
 import org.onosproject.core.ApplicationId;
-import org.onosproject.event.AbstractListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.device.DeviceEvent;
 import org.onosproject.net.device.DeviceListener;
@@ -54,7 +48,12 @@ import org.onosproject.net.provider.AbstractProviderRegistry;
 import org.onosproject.net.provider.AbstractProviderService;
 import org.slf4j.Logger;
 
-import com.google.common.collect.Sets;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.Set;
+
+import static org.slf4j.LoggerFactory.getLogger;
 
 /**
  * Provides implementation of the group service APIs.
@@ -67,8 +66,8 @@ public class GroupManager
 
     private final Logger log = getLogger(getClass());
 
-    private final AbstractListenerRegistry<GroupEvent, GroupListener>
-                listenerRegistry = new AbstractListenerRegistry<>();
+    private final ListenerRegistry<GroupEvent, GroupListener>
+                listenerRegistry = new ListenerRegistry<>();
     private final GroupStoreDelegate delegate = new InternalGroupStoreDelegate();
     private final DeviceListener deviceListener = new InternalDeviceListener();
 

@@ -15,19 +15,17 @@
  */
 package org.onosproject.net.host.impl;
 
-import static com.google.common.base.Preconditions.checkNotNull;
-import static org.slf4j.LoggerFactory.getLogger;
-
-import java.util.Set;
-
 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.onosproject.event.AbstractListenerRegistry;
+import org.onlab.packet.IpAddress;
+import org.onlab.packet.MacAddress;
+import org.onlab.packet.VlanId;
 import org.onosproject.event.EventDeliveryService;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.net.ConnectPoint;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.Host;
@@ -47,11 +45,13 @@ import org.onosproject.net.host.PortAddresses;
 import org.onosproject.net.packet.PacketService;
 import org.onosproject.net.provider.AbstractProviderRegistry;
 import org.onosproject.net.provider.AbstractProviderService;
-import org.onlab.packet.IpAddress;
-import org.onlab.packet.MacAddress;
-import org.onlab.packet.VlanId;
 import org.slf4j.Logger;
 
+import java.util.Set;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static org.slf4j.LoggerFactory.getLogger;
+
 /**
  * Provides basic implementation of the host SB & NB APIs.
  */
@@ -64,8 +64,8 @@ public class HostManager
     public static final String HOST_ID_NULL = "Host ID cannot be null";
     private final Logger log = getLogger(getClass());
 
-    private final AbstractListenerRegistry<HostEvent, HostListener>
-            listenerRegistry = new AbstractListenerRegistry<>();
+    private final ListenerRegistry<HostEvent, HostListener>
+            listenerRegistry = new ListenerRegistry<>();
 
     private HostStoreDelegate delegate = new InternalStoreDelegate();
 

@@ -24,7 +24,7 @@ import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.apache.felix.scr.annotations.Service;
 import org.onosproject.core.CoreService;
 import org.onosproject.core.IdGenerator;
-import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
 import org.onosproject.net.flow.FlowRule;
 import org.onosproject.net.flow.FlowRuleOperations;
@@ -83,8 +83,8 @@ public class IntentManager
     private static final EnumSet<IntentState> RECOMPILE
             = EnumSet.of(INSTALL_REQ, FAILED, WITHDRAW_REQ);
 
-    private final AbstractListenerRegistry<IntentEvent, IntentListener>
-            listenerRegistry = new AbstractListenerRegistry<>();
+    private final ListenerRegistry<IntentEvent, IntentListener>
+            listenerRegistry = new ListenerRegistry<>();
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected CoreService coreService;

@@ -15,16 +15,17 @@
  */
 package org.onosproject.net.link.impl;
 
-import java.util.Set;
-
+import com.google.common.base.Predicate;
+import com.google.common.collect.FluentIterable;
+import com.google.common.collect.Sets;
 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.onosproject.event.AbstractListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.net.ConnectPoint;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.Link;
@@ -47,9 +48,7 @@ import org.onosproject.net.provider.AbstractProviderRegistry;
 import org.onosproject.net.provider.AbstractProviderService;
 import org.slf4j.Logger;
 
-import com.google.common.base.Predicate;
-import com.google.common.collect.FluentIterable;
-import com.google.common.collect.Sets;
+import java.util.Set;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 import static org.slf4j.LoggerFactory.getLogger;
@@ -69,8 +68,8 @@ public class LinkManager
 
     private final Logger log = getLogger(getClass());
 
-    protected final AbstractListenerRegistry<LinkEvent, LinkListener>
-            listenerRegistry = new AbstractListenerRegistry<>();
+    protected final ListenerRegistry<LinkEvent, LinkListener>
+            listenerRegistry = new ListenerRegistry<>();
 
     private final LinkStoreDelegate delegate = new InternalStoreDelegate();
 

@@ -21,7 +21,7 @@ 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.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
 import org.onosproject.net.Link;
 import org.onosproject.net.intent.IntentId;
@@ -66,8 +66,8 @@ public class LinkResourceManager implements LinkResourceService {
 
     private final Logger log = getLogger(getClass());
 
-    protected final AbstractListenerRegistry<LinkResourceEvent, LinkResourceListener>
-            listenerRegistry = new AbstractListenerRegistry<>();
+    protected final ListenerRegistry<LinkResourceEvent, LinkResourceListener>
+            listenerRegistry = new ListenerRegistry<>();
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     private LinkResourceStore store;

@@ -21,7 +21,7 @@ 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.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.Event;
 import org.onosproject.event.EventDeliveryService;
 import org.onosproject.net.ConnectPoint;
@@ -69,8 +69,8 @@ public class TopologyManager
 
     private final Logger log = getLogger(getClass());
 
-    private final AbstractListenerRegistry<TopologyEvent, TopologyListener>
-            listenerRegistry = new AbstractListenerRegistry<>();
+    private final ListenerRegistry<TopologyEvent, TopologyListener>
+            listenerRegistry = new ListenerRegistry<>();
 
     private TopologyStoreDelegate delegate = new InternalStoreDelegate();
 

@@ -15,12 +15,6 @@
  */
 package org.onosproject.net.tunnel.impl;
 
-import static org.slf4j.LoggerFactory.getLogger;
-
-import java.util.Collection;
-import java.util.Set;
-import java.util.concurrent.ExecutorService;
-
 import org.apache.felix.scr.annotations.Activate;
 import org.apache.felix.scr.annotations.Component;
 import org.apache.felix.scr.annotations.Deactivate;
@@ -28,8 +22,8 @@ import org.apache.felix.scr.annotations.Reference;
 import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.apache.felix.scr.annotations.Service;
 import org.onosproject.core.CoreService;
-import org.onosproject.event.AbstractListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.net.ConnectPoint;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.Path;
@@ -41,6 +35,7 @@ import org.onosproject.net.provider.ProviderId;
 import org.onosproject.net.resource.BandwidthResource;
 import org.onosproject.net.tunnel.Label;
 import org.onosproject.net.tunnel.Tunnel;
+import org.onosproject.net.tunnel.Tunnel.Type;
 import org.onosproject.net.tunnel.TunnelAdminService;
 import org.onosproject.net.tunnel.TunnelDescription;
 import org.onosproject.net.tunnel.TunnelEvent;
@@ -52,9 +47,14 @@ import org.onosproject.net.tunnel.TunnelProviderService;
 import org.onosproject.net.tunnel.TunnelService;
 import org.onosproject.net.tunnel.TunnelStore;
 import org.onosproject.net.tunnel.TunnelStoreDelegate;
-import org.onosproject.net.tunnel.Tunnel.Type;
 import org.slf4j.Logger;
 
+import java.util.Collection;
+import java.util.Set;
+import java.util.concurrent.ExecutorService;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
 /**
  * Provides implementation of the tunnel NB/SB APIs.
  */
@@ -67,8 +67,8 @@ public class TunnelManager extends AbstractProviderRegistry<TunnelProvider, Tunn
 
     private final Logger log = getLogger(getClass());
 
-    protected final AbstractListenerRegistry<TunnelEvent, TunnelListener>
-            listenerRegistry = new AbstractListenerRegistry<>();
+    protected final ListenerRegistry<TunnelEvent, TunnelListener>
+            listenerRegistry = new ListenerRegistry<>();
 
     private final TunnelStoreDelegate delegate = new InternalStoreDelegate();
     private final InternalTunnelListener tunnelListener = new InternalTunnelListener();

@@ -33,7 +33,7 @@ import org.onosproject.cluster.LeadershipEvent;
 import org.onosproject.cluster.LeadershipEventListener;
 import org.onosproject.cluster.LeadershipService;
 import org.onosproject.cluster.NodeId;
-import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
 import org.onosproject.store.cluster.messaging.ClusterCommunicationService;
 import org.onosproject.store.cluster.messaging.ClusterMessage;
@@ -109,7 +109,7 @@ public class HazelcastLeadershipService implements LeadershipService {
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected EventDeliveryService eventDispatcher;
 
-    private AbstractListenerRegistry<LeadershipEvent, LeadershipEventListener>
+    private ListenerRegistry<LeadershipEvent, LeadershipEventListener>
         listenerRegistry;
     private final Map<String, Topic> topics = Maps.newConcurrentMap();
     private NodeId localNodeId;
@@ -122,7 +122,7 @@ public class HazelcastLeadershipService implements LeadershipService {
     @Activate
     protected void activate() {
         localNodeId = clusterService.getLocalNode().id();
-        listenerRegistry = new AbstractListenerRegistry<>();
+        listenerRegistry = new ListenerRegistry<>();
         eventDispatcher.addSink(LeadershipEvent.class, listenerRegistry);
 
         TopicConfig topicConfig = new TopicConfig();

@@ -19,7 +19,7 @@ import org.onosproject.cluster.LeadershipEvent;
 import org.onosproject.cluster.LeadershipEventListener;
 import org.onosproject.cluster.LeadershipService;
 import org.onosproject.cluster.NodeId;
-import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
 import org.onosproject.store.cluster.messaging.ClusterCommunicationService;
 import org.onosproject.store.cluster.messaging.MessageSubject;
@@ -85,7 +85,7 @@ public class DistributedLeadershipManager implements LeadershipService {
     private ConsistentMap<String, NodeId> leaderMap;
     private ConsistentMap<String, List<NodeId>> candidateMap;
 
-    private AbstractListenerRegistry<LeadershipEvent, LeadershipEventListener>
+    private ListenerRegistry<LeadershipEvent, LeadershipEventListener>
         listenerRegistry;
     private final Map<String, Leadership> leaderBoard = Maps.newConcurrentMap();
     private final Map<String, Leadership> candidateBoard = Maps.newConcurrentMap();
@@ -135,7 +135,7 @@ public class DistributedLeadershipManager implements LeadershipService {
         leadershipStatusBroadcaster.scheduleWithFixedDelay(
                 this::sendLeadershipStatus, 0, LEADERSHIP_STATUS_UPDATE_INTERVAL_SEC, TimeUnit.SECONDS);
 
-        listenerRegistry = new AbstractListenerRegistry<>();
+        listenerRegistry = new ListenerRegistry<>();
         eventDispatcher.addSink(LeadershipEvent.class, listenerRegistry);
 
         log.info("Started");

@@ -15,15 +15,9 @@
  */
 package org.onosproject.store.flow.impl;
 
-import static com.google.common.base.Preconditions.checkNotNull;
-import static org.slf4j.LoggerFactory.getLogger;
-import static org.onosproject.store.flow.ReplicaInfoEvent.Type.MASTER_CHANGED;
-import static org.onosproject.store.flow.ReplicaInfoEvent.Type.BACKUPS_CHANGED;
-
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
-
+import com.google.common.base.Objects;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Maps;
 import org.apache.felix.scr.annotations.Activate;
 import org.apache.felix.scr.annotations.Component;
 import org.apache.felix.scr.annotations.Deactivate;
@@ -32,8 +26,8 @@ import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.apache.felix.scr.annotations.Service;
 import org.onosproject.cluster.NodeId;
 import org.onosproject.cluster.RoleInfo;
-import org.onosproject.event.AbstractListenerRegistry;
 import org.onosproject.event.EventDeliveryService;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.mastership.MastershipEvent;
 import org.onosproject.mastership.MastershipListener;
 import org.onosproject.mastership.MastershipService;
@@ -44,9 +38,14 @@ import org.onosproject.store.flow.ReplicaInfoEventListener;
 import org.onosproject.store.flow.ReplicaInfoService;
 import org.slf4j.Logger;
 
-import com.google.common.base.Objects;
-import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Maps;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static org.onosproject.store.flow.ReplicaInfoEvent.Type.BACKUPS_CHANGED;
+import static org.onosproject.store.flow.ReplicaInfoEvent.Type.MASTER_CHANGED;
+import static org.slf4j.LoggerFactory.getLogger;
 
 /**
  * Manages replica placement information.
@@ -65,8 +64,8 @@ public class ReplicaInfoManager implements ReplicaInfoService {
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected MastershipService mastershipService;
 
-    protected final AbstractListenerRegistry<ReplicaInfoEvent, ReplicaInfoEventListener>
-        listenerRegistry = new AbstractListenerRegistry<>();
+    protected final ListenerRegistry<ReplicaInfoEvent, ReplicaInfoEventListener>
+        listenerRegistry = new ListenerRegistry<>();
 
     private final Map<DeviceId, ReplicaInfo> deviceReplicaInfoMap = Maps.newConcurrentMap();
 

@@ -15,25 +15,18 @@
  */
 package org.onosproject.store.flow.impl;
 
-import static com.google.common.base.Preconditions.checkState;
-import static org.junit.Assert.*;
-
-import java.util.Collections;
-import java.util.Map;
-import java.util.LinkedList;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.TimeUnit;
-
+import com.google.common.base.Optional;
+import com.google.common.collect.Maps;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.onosproject.cluster.NodeId;
 import org.onosproject.cluster.RoleInfo;
-import org.onosproject.event.AbstractListenerRegistry;
 import org.onosproject.event.DefaultEventSinkRegistry;
 import org.onosproject.event.Event;
 import org.onosproject.event.EventDeliveryService;
 import org.onosproject.event.EventSink;
+import org.onosproject.event.ListenerRegistry;
 import org.onosproject.mastership.MastershipEvent;
 import org.onosproject.mastership.MastershipEvent.Type;
 import org.onosproject.mastership.MastershipListener;
@@ -45,8 +38,15 @@ import org.onosproject.store.flow.ReplicaInfoEvent;
 import org.onosproject.store.flow.ReplicaInfoEventListener;
 import org.onosproject.store.flow.ReplicaInfoService;
 
-import com.google.common.base.Optional;
-import com.google.common.collect.Maps;
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.Map;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import static com.google.common.base.Preconditions.checkState;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
 public class ReplicaInfoManagerTest {
 
@@ -58,14 +58,14 @@ public class ReplicaInfoManagerTest {
     private ReplicaInfoManager mgr;
     private ReplicaInfoService service;
 
-    private AbstractListenerRegistry<MastershipEvent, MastershipListener>
+    private ListenerRegistry<MastershipEvent, MastershipListener>
         mastershipListenerRegistry;
     private TestEventDispatcher eventDispatcher;
 
 
     @Before
     public void setUp() throws Exception {
-        mastershipListenerRegistry = new AbstractListenerRegistry<>();
+        mastershipListenerRegistry = new ListenerRegistry<>();
 
         mgr = new ReplicaInfoManager();
         service = mgr;

@@ -17,7 +17,7 @@
 
 package org.onosproject.ui.impl.topo;
 
-import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.ListenerRegistry;
 import org.slf4j.Logger;
 
 import java.util.HashSet;
@@ -31,7 +31,7 @@ import static org.slf4j.LoggerFactory.getLogger;
  */
 // package private
 class ModelListenerRegistry
-        extends AbstractListenerRegistry<TopoUiEvent, TopoUiListener> {
+        extends ListenerRegistry<TopoUiEvent, TopoUiListener> {
 
     private final Logger log = getLogger(getClass());
 
@@ -58,4 +58,9 @@ class ModelListenerRegistry
             removeListener(z);
         }
     }
+
+    @Override
+    protected boolean checkForNonRegistrant() {
+        return false;
+    }
 }

@@ -143,12 +143,7 @@ public class TopoUiModelManager implements TopoUiModelService {
 
     @Override
     public void removeListener(TopoUiListener listener) {
-        // we don't really care if the listener is not listed...
-        try {
-            listenerRegistry.removeListener(listener);
-        } catch (IllegalArgumentException e) {
-            log.debug("Oops, listener not registered: {}", listener);
-        }
+        listenerRegistry.removeListener(listener);
     }
 
     @Override