svn commit: r1349298 - /tomcat/trunk/java/org/apache/catalina/core/ContainerBase.java

[markt]

Author: markt
Date: Tue Jun 12 12:38:20 2012
New Revision: 1349298

URL: http://svn.apache.org/viewvc?rev=1349298&view=rev
Log:
Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=52999
Remove synchronization bottleneck in container event handling

Modified:
    tomcat/trunk/java/org/apache/catalina/core/ContainerBase.java

Modified: tomcat/trunk/java/org/apache/catalina/core/ContainerBase.java
URL: 
http://svn.apache.org/viewvc/tomcat/trunk/java/org/apache/catalina/core/ContainerBase.java?rev=1349298&r1=1349297&r2=1349298&view=diff
==============================================================================
--- tomcat/trunk/java/org/apache/catalina/core/ContainerBase.java (original)
+++ tomcat/trunk/java/org/apache/catalina/core/ContainerBase.java Tue Jun 12 
12:38:20 2012
@@ -180,7 +180,9 @@ public abstract class ContainerBase exte
     /**
      * The container event listeners for this Container.
      */
-    protected ArrayList<ContainerListener> listeners = new 
ArrayList<ContainerListener>();
+    protected ArrayList<ContainerListener> listeners =
+            new ArrayList<ContainerListener>();
+    protected ReadWriteLock listenersLock = new ReentrantReadWriteLock();
 
 
     /**
@@ -896,10 +898,13 @@ public abstract class ContainerBase exte
     @Override
     public void addContainerListener(ContainerListener listener) {
 
-        synchronized (listeners) {
+        Lock write = listenersLock.writeLock();
+        write.lock();
+        try {
             listeners.add(listener);
+        } finally {
+            write.unlock();
         }
-
     }
 
 
@@ -957,12 +962,15 @@ public abstract class ContainerBase exte
     @Override
     public ContainerListener[] findContainerListeners() {
 
-        synchronized (listeners) {
+        Lock read = listenersLock.readLock();
+        read.lock();
+        try {
             ContainerListener[] results =
                 new ContainerListener[listeners.size()];
             return listeners.toArray(results);
+        } finally {
+            read.unlock();
         }
-
     }
 
 
@@ -1017,10 +1025,13 @@ public abstract class ContainerBase exte
     @Override
     public void removeContainerListener(ContainerListener listener) {
 
-        synchronized (listeners) {
+        Lock write = listenersLock.writeLock();
+        write.lock();
+        try {
             listeners.remove(listener);
+        } finally {
+            write.unlock();
         }
-
     }
 
 
@@ -1365,16 +1376,31 @@ public abstract class ContainerBase exte
     @Override
     public void fireContainerEvent(String type, Object data) {
 
-        if (listeners.size() < 1)
-            return;
-        ContainerEvent event = new ContainerEvent(this, type, data);
-        ContainerListener list[] = new ContainerListener[0];
-        synchronized (listeners) {
-            list = listeners.toArray(list);
+        /*
+         * Implementation note
+         * There are two options here.
+         * 1) Take a copy of listeners and fire the events outside of the read
+         *    lock
+         * 2) Don't take a copy and fire the events inside the read lock
+         *
+         * Approach 2 has been used here since holding the read lock only
+         * prevents writes and that is preferable to creating lots of array
+         * objects. Since writes occur on start / stop (unless an external
+         * management tool is used) then holding the read lock for a relatively
+         * long time should not be an issue.
+         */
+        Lock read = listenersLock.readLock();
+        read.lock();
+        try {
+            if (listeners.size() < 1)
+                return;
+            ContainerEvent event = new ContainerEvent(this, type, data);
+            for (ContainerListener listener : listeners) {
+                listener.containerEvent(event);
+            }
+        } finally {
+            read.unlock();
         }
-        for (int i = 0; i < list.length; i++)
-            list[i].containerEvent(event);
-
     }
 
 



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