//
// ========================================================================
-// Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
+// Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
/**
* A facility to detect improper usage of resource pools.
* <p>
- * Resource pools usually have a method to acquire a pooled resource
- * and a method to released it back to the pool.
+ * Resource pools usually have a method to acquire a pooled resource and a method to released it back to the pool.
* <p>
- * To detect if client code acquires a resource but never releases it,
- * the resource pool can be modified to use a {@link LeakDetector}.
- * The modified resource pool should call {@link #acquired(Object)} every time
- * the method to acquire a resource is called, and {@link #released(Object)}
- * every time the method to release the resource is called.
+ * To detect if client code acquires a resource but never releases it, the resource pool can be modified to use a
+ * {@link LeakDetector}. The modified resource pool should call {@link #acquired(Object)} every time the method to
+ * acquire a resource is called, and {@link #released(Object)} every time the method to release the resource is called.
* {@link LeakDetector} keeps track of these resources and invokes method
- * {@link #leaked(org.eclipse.jetty.util.LeakDetector.LeakInfo)} when it detects that a resource
- * has been leaked (that is, acquired but never released).
+ * {@link #leaked(org.eclipse.jetty.util.LeakDetector.LeakInfo)} when it detects that a resource has been leaked (that
+ * is, acquired but never released).
* <p>
- * To detect whether client code releases a resource without having
- * acquired it, the resource pool can be modified to check the return value
- * of {@link #released(Object)}: if false, it means that the resource was
- * not acquired.
+ * To detect whether client code releases a resource without having acquired it, the resource pool can be modified to
+ * check the return value of {@link #released(Object)}: if false, it means that the resource was not acquired.
* <p>
* IMPLEMENTATION NOTES
* <p>
- * This class relies on {@link System#identityHashCode(Object)} to create
- * a unique id for each resource passed to {@link #acquired(Object)} and
- * {@link #released(Object)}. {@link System#identityHashCode(Object)} does
- * not guarantee that it will not generate the same number for different
- * objects, but in practice the chance of collision is rare.
+ * This class relies on {@link System#identityHashCode(Object)} to create a unique id for each resource passed to
+ * {@link #acquired(Object)} and {@link #released(Object)}. {@link System#identityHashCode(Object)} does not guarantee
+ * that it will not generate the same number for different objects, but in practice the chance of collision is rare.
* <p>
- * {@link LeakDetector} uses {@link PhantomReference}s to detect leaks.
- * {@link PhantomReference}s are enqueued in their {@link ReferenceQueue}
- * <em>after</em> they have been garbage collected (differently from
- * {@link WeakReference}s that are enqueued <em>before</em>).
- * Since the resource is now garbage collected, {@link LeakDetector} checks
- * whether it has been released and if not, it reports a leak.
- * Using {@link PhantomReference}s is better than overriding {@link #finalize()}
- * and works also in those cases where {@link #finalize()} is not
- * overridable.
+ * {@link LeakDetector} uses {@link PhantomReference}s to detect leaks. {@link PhantomReference}s are enqueued in their
+ * {@link ReferenceQueue} <em>after</em> they have been garbage collected (differently from {@link WeakReference}s that
+ * are enqueued <em>before</em>). Since the resource is now garbage collected, {@link LeakDetector} checks whether it
+ * has been released and if not, it reports a leak. Using {@link PhantomReference}s is better than overriding
+ * {@link #finalize()} and works also in those cases where {@link #finalize()} is not overridable.
*
* @param <T> the resource type.
*/
* Tracks the resource as been acquired.
*
* @param resource the resource that has been acquired
- * @return whether the resource has been tracked
+ * @return true whether the resource has been acquired normally, false if the resource has detected a leak (meaning
+ * that another acquire occurred before a release of the same resource)
* @see #released(Object)
*/
public boolean acquired(T resource)
{
String id = id(resource);
- return resources.putIfAbsent(id, new LeakInfo(resource, id)) == null;
+ LeakInfo info = resources.putIfAbsent(id, new LeakInfo(resource,id));
+ if (info != null)
+ {
+ // Leak detected, prior acquire exists (not released) or id clash.
+ return false;
+ }
+ // Normal behavior.
+ return true;
}
/**
* Tracks the resource as been released.
*
* @param resource the resource that has been released
- * @return whether the resource has been acquired
+ * @return true whether the resource has been released normally (based on a previous acquire). false if the resource
+ * has been released without a prior acquire (such as a double release scenario)
* @see #acquired(Object)
*/
public boolean released(T resource)
{
String id = id(resource);
- return resources.remove(id) != null;
+ LeakInfo info = resources.remove(id);
+ if (info != null)
+ {
+ // Normal behavior.
+ return true;
+ }
+
+ // Leak detected (released without acquire).
+ return false;
}
/**
* @param resource the resource to generate the unique ID for
* @return the unique ID of the given resource
*/
- protected String id(T resource)
+ public String id(T resource)
{
return String.valueOf(System.identityHashCode(resource));
}
protected void doStart() throws Exception
{
super.doStart();
- thread = new Thread(this, getClass().getSimpleName());
+ thread = new Thread(this,getClass().getSimpleName());
thread.setDaemon(true);
thread.start();
}
@Override
protected void doStop() throws Exception
{
- thread.interrupt();
super.doStop();
+ thread.interrupt();
}
@Override
{
@SuppressWarnings("unchecked")
LeakInfo leakInfo = (LeakInfo)queue.remove();
- LOG.debug("Resource GC'ed: {}", leakInfo);
+ if (LOG.isDebugEnabled())
+ LOG.debug("Resource GC'ed: {}",leakInfo);
if (resources.remove(leakInfo.id) != null)
leaked(leakInfo);
}
*/
protected void leaked(LeakInfo leakInfo)
{
- LOG.warn("Resource leaked: " + leakInfo.description, leakInfo.stackFrames);
+ LOG.warn("Resource leaked: " + leakInfo.description,leakInfo.stackFrames);
}
/**
private LeakInfo(T referent, String id)
{
- super(referent, queue);
+ super(referent,queue);
this.id = id;
this.description = referent.toString();
this.stackFrames = new Throwable();
projects / gigi.git / blobdiff