BUG-509: improve memory efficiency of ListenerTree

As it turns out, we do not need a Set<>, but rather a collection. We do
not expect major modifications of listeners, but memory efficiency and
iteration speed are required. Thus turn the HashSet into an ArrayList.

Also rename DataChangeListenerRegistration to
DataChangeListenerRegistrationImpl, so that the interface itself can be
imported and used as a shortname. This has the nice effect of rendering
a nasty SuppressWarnings completely unneeded.

Change-Id: I100337651c3b42c715978708bc98cf24ce5bf703
Signed-off-by: Robert Varga <rovarga@cisco.com>

diff --git a/opendaylight/md-sal/sal-dom-broker/src/main/java/org/opendaylight/controller/md/sal/dom/store/impl/tree/ListenerTree.java b/opendaylight/md-sal/sal-dom-broker/src/main/java/org/opendaylight/controller/md/sal/dom/store/impl/tree/ListenerTree.java
index 58a0c69bb06a94e59d97f9dc88aee0ea71cef4ca..83cfcaca18e9d3e3ad403f5665a91843867edc3f 100644 (file)
--- a/opendaylight/md-sal/sal-dom-broker/src/main/java/org/opendaylight/controller/md/sal/dom/store/impl/tree/ListenerTree.java
+++ b/opendaylight/md-sal/sal-dom-broker/src/main/java/org/opendaylight/controller/md/sal/dom/store/impl/tree/ListenerTree.java
@@ -9,9 +9,9 @@ package org.opendaylight.controller.md.sal.dom.store.impl.tree;
 
 import java.lang.ref.Reference;
 import java.lang.ref.WeakReference;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.Map;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReadWriteLock;
@@ -21,6 +21,7 @@ import javax.annotation.concurrent.GuardedBy;
 
 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataBroker.DataChangeScope;
 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeListener;
+import org.opendaylight.controller.md.sal.dom.store.impl.DataChangeListenerRegistration;
 import org.opendaylight.yangtools.concepts.AbstractListenerRegistration;
 import org.opendaylight.yangtools.concepts.Identifiable;
 import org.opendaylight.yangtools.yang.data.api.InstanceIdentifier;
@@ -61,12 +62,12 @@ public final class ListenerTree {
 
         try {
             Node walkNode = rootNode;
-            for(PathArgument arg : path.getPath()) {
+            for (final PathArgument arg : path.getPath()) {
                 walkNode = walkNode.ensureChild(arg);
             }
 
             final Node node = walkNode;
-            DataChangeListenerRegistration<L> listenerReg = new DataChangeListenerRegistration<L>(listener) {
+            DataChangeListenerRegistration<L> reg = new DataChangeListenerRegistrationImpl<L>(listener) {
                 @Override
                 public DataChangeScope getScope() {
                     return scope;
@@ -101,8 +102,8 @@ public final class ListenerTree {
                 }
             };
 
-            node.addListener(listenerReg);
-            return listenerReg;
+            node.addListener(reg);
+            return reg;
         } finally {
             // Always release the lock
             rwLock.writeLock().unlock();
@@ -155,7 +156,7 @@ public final class ListenerTree {
      * unclosed.
      */
     public static final class Node implements StoreTreeNode<Node>, Identifiable<PathArgument> {
-        private final HashSet<DataChangeListenerRegistration<?>> listeners = new HashSet<>();
+        private final Collection<DataChangeListenerRegistration<?>> listeners = new ArrayList<>();
         private final Map<PathArgument, Node> children = new HashMap<>();
         private final PathArgument identifier;
         private final Reference<Node> parent;
@@ -182,13 +183,12 @@ public final class ListenerTree {
          *
          * @return the list of current listeners
          */
-        @SuppressWarnings({ "rawtypes", "unchecked" })
-        public Collection<org.opendaylight.controller.md.sal.dom.store.impl.DataChangeListenerRegistration<?>> getListeners() {
-            return (Collection) listeners;
+        public Collection<DataChangeListenerRegistration<?>> getListeners() {
+            return listeners;
         }
 
         private Node ensureChild(final PathArgument child) {
-            Node potential = (children.get(child));
+            Node potential = children.get(child);
             if (potential == null) {
                 potential = new Node(this, child);
                 children.put(child, potential);
@@ -201,7 +201,7 @@ public final class ListenerTree {
             LOG.debug("Listener {} registered", listener);
         }
 
-        private void removeListener(final DataChangeListenerRegistration<?> listener) {
+        private void removeListener(final DataChangeListenerRegistrationImpl<?> listener) {
             listeners.remove(listener);
             LOG.debug("Listener {} unregistered", listener);
 
@@ -222,12 +222,10 @@ public final class ListenerTree {
         }
     }
 
-    private abstract static class DataChangeListenerRegistration<T extends AsyncDataChangeListener<InstanceIdentifier, NormalizedNode<?, ?>>> extends AbstractListenerRegistration<T> implements
-    org.opendaylight.controller.md.sal.dom.store.impl.DataChangeListenerRegistration<T> {
-
-        public DataChangeListenerRegistration(final T listener) {
+    private abstract static class DataChangeListenerRegistrationImpl<T extends AsyncDataChangeListener<InstanceIdentifier, NormalizedNode<?, ?>>> extends AbstractListenerRegistration<T> //
+    implements DataChangeListenerRegistration<T> {
+        public DataChangeListenerRegistrationImpl(final T listener) {
             super(listener);
         }
     }
-
 }