ThreadLocalLeakPreventionListener.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.catalina.core;
import java.util.concurrent.Executor;
import org.apache.catalina.Container;
import org.apache.catalina.ContainerEvent;
import org.apache.catalina.ContainerListener;
import org.apache.catalina.Context;
import org.apache.catalina.Engine;
import org.apache.catalina.Host;
import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleEvent;
import org.apache.catalina.LifecycleListener;
import org.apache.catalina.Server;
import org.apache.catalina.Service;
import org.apache.catalina.connector.Connector;
import org.apache.coyote.ProtocolHandler;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.util.threads.ThreadPoolExecutor;
/**
* A {@link LifecycleListener} that triggers the renewal of threads in Executor pools when a {@link Context} is being
* stopped to avoid thread-local related memory leaks.
* <p>
* Note : active threads will be renewed one by one when they come back to the pool after executing their task, see
* {@link org.apache.tomcat.util.threads.ThreadPoolExecutor}.afterExecute().
* <p>
* This listener must only be nested within {@link Server} elements.
*/
public class ThreadLocalLeakPreventionListener implements LifecycleListener, ContainerListener {
private static final Log log = LogFactory.getLog(ThreadLocalLeakPreventionListener.class);
private volatile boolean serverStopping = false;
/**
* The string manager for this package.
*/
protected static final StringManager sm = StringManager.getManager(ThreadLocalLeakPreventionListener.class);
/**
* Listens for {@link LifecycleEvent} for the start of the {@link Server} to initialize itself and then for
* after_stop events of each {@link Context}.
*/
@Override
public void lifecycleEvent(LifecycleEvent event) {
try {
Lifecycle lifecycle = event.getLifecycle();
if (Lifecycle.AFTER_START_EVENT.equals(event.getType()) && lifecycle instanceof Server) {
// when the server starts, we register ourself as listener for
// all context
// as well as container event listener so that we know when new
// Context are deployed
Server server = (Server) lifecycle;
registerListenersForServer(server);
}
if (Lifecycle.BEFORE_STOP_EVENT.equals(event.getType()) && lifecycle instanceof Server) {
// Server is shutting down, so thread pools will be shut down so
// there is no need to clean the threads
serverStopping = true;
}
if (Lifecycle.AFTER_STOP_EVENT.equals(event.getType()) && lifecycle instanceof Context) {
stopIdleThreads((Context) lifecycle);
}
} catch (Exception e) {
String msg = sm.getString("threadLocalLeakPreventionListener.lifecycleEvent.error", event);
log.error(msg, e);
}
}
@Override
public void containerEvent(ContainerEvent event) {
try {
String type = event.getType();
if (Container.ADD_CHILD_EVENT.equals(type)) {
processContainerAddChild(event.getContainer(), (Container) event.getData());
} else if (Container.REMOVE_CHILD_EVENT.equals(type)) {
processContainerRemoveChild(event.getContainer(), (Container) event.getData());
}
} catch (Exception e) {
String msg = sm.getString("threadLocalLeakPreventionListener.containerEvent.error", event);
log.error(msg, e);
}
}
private void registerListenersForServer(Server server) {
for (Service service : server.findServices()) {
Engine engine = service.getContainer();
if (engine != null) {
engine.addContainerListener(this);
registerListenersForEngine(engine);
}
}
}
private void registerListenersForEngine(Engine engine) {
for (Container hostContainer : engine.findChildren()) {
Host host = (Host) hostContainer;
host.addContainerListener(this);
registerListenersForHost(host);
}
}
private void registerListenersForHost(Host host) {
for (Container contextContainer : host.findChildren()) {
Context context = (Context) contextContainer;
registerContextListener(context);
}
}
private void registerContextListener(Context context) {
context.addLifecycleListener(this);
}
protected void processContainerAddChild(Container parent, Container child) {
if (log.isDebugEnabled()) {
log.debug("Process addChild[parent=" + parent + ",child=" + child + "]");
}
if (child instanceof Context) {
registerContextListener((Context) child);
} else if (child instanceof Engine) {
registerListenersForEngine((Engine) child);
} else if (child instanceof Host) {
registerListenersForHost((Host) child);
}
}
protected void processContainerRemoveChild(Container parent, Container child) {
if (log.isDebugEnabled()) {
log.debug("Process removeChild[parent=" + parent + ",child=" + child + "]");
}
if (child instanceof Context) {
Context context = (Context) child;
context.removeLifecycleListener(this);
} else if (child instanceof Host || child instanceof Engine) {
child.removeContainerListener(this);
}
}
/**
* Updates each ThreadPoolExecutor with the current time, which is the time when a context is being stopped.
*
* @param context the context being stopped, used to discover all the Connectors of its parent Service.
*/
private void stopIdleThreads(Context context) {
if (serverStopping) {
return;
}
if (!(context instanceof StandardContext) ||
!((StandardContext) context).getRenewThreadsWhenStoppingContext()) {
if (log.isTraceEnabled()) {
log.trace("Not renewing threads when the context is stopping. It is not configured to do it.");
}
return;
}
Engine engine = (Engine) context.getParent().getParent();
Service service = engine.getService();
Connector[] connectors = service.findConnectors();
if (connectors != null) {
for (Connector connector : connectors) {
ProtocolHandler handler = connector.getProtocolHandler();
Executor executor = null;
if (handler != null) {
executor = handler.getExecutor();
}
if (executor instanceof ThreadPoolExecutor) {
ThreadPoolExecutor threadPoolExecutor = (ThreadPoolExecutor) executor;
threadPoolExecutor.contextStopping();
} else if (executor instanceof StandardThreadExecutor) {
StandardThreadExecutor stdThreadExecutor = (StandardThreadExecutor) executor;
stdThreadExecutor.contextStopping();
}
}
}
}
}