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/*
* 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.tomcat.websocket;
import java.io.IOException;
import java.nio.channels.AsynchronousChannelGroup;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.util.threads.ThreadPoolExecutor;
/**
* This is a utility class that enables multiple {@link WsWebSocketContainer}
* instances to share a single {@link AsynchronousChannelGroup} while ensuring
* that the group is destroyed when no longer required.
*/
public class AsyncChannelGroupUtil {
private static final StringManager sm =
StringManager.getManager(AsyncChannelGroupUtil.class);
private static AsynchronousChannelGroup group = null;
private static int usageCount = 0;
private static final Object lock = new Object();
private AsyncChannelGroupUtil() {
// Hide the default constructor
}
public static AsynchronousChannelGroup register() {
synchronized (lock) {
if (usageCount == 0) {
group = createAsynchronousChannelGroup();
}
usageCount++;
return group;
}
}
public static void unregister() {
synchronized (lock) {
usageCount--;
if (usageCount == 0) {
group.shutdown();
group = null;
}
}
}
private static AsynchronousChannelGroup createAsynchronousChannelGroup() {
// Need to do this with the right thread context class loader else the
// first web app to call this will trigger a leak
ClassLoader original = Thread.currentThread().getContextClassLoader();
try {
Thread.currentThread().setContextClassLoader(
AsyncIOThreadFactory.class.getClassLoader());
// These are the same settings as the default
// AsynchronousChannelGroup
int initialSize = Runtime.getRuntime().availableProcessors();
ExecutorService executorService = new ThreadPoolExecutor(
0,
Integer.MAX_VALUE,
Long.MAX_VALUE, TimeUnit.MILLISECONDS,
new SynchronousQueue<>(),
new AsyncIOThreadFactory());
try {
return AsynchronousChannelGroup.withCachedThreadPool(
executorService, initialSize);
} catch (IOException e) {
// No good reason for this to happen.
throw new IllegalStateException(sm.getString("asyncChannelGroup.createFail"));
}
} finally {
Thread.currentThread().setContextClassLoader(original);
}
}
private static class AsyncIOThreadFactory implements ThreadFactory {
static {
// Load NewThreadPrivilegedAction since newThread() will not be able
// to if called from an InnocuousThread.
// See https://bz.apache.org/bugzilla/show_bug.cgi?id=57490
NewThreadPrivilegedAction.load();
}
@Override
public Thread newThread(final Runnable r) {
// Create the new Thread within a doPrivileged block to ensure that
// the thread inherits the current ProtectionDomain which is
// essential to be able to use this with a Java Applet. See
// https://bz.apache.org/bugzilla/show_bug.cgi?id=57091
return AccessController.doPrivileged(new NewThreadPrivilegedAction(r));
}
// Non-anonymous class so that AsyncIOThreadFactory can load it
// explicitly
private static class NewThreadPrivilegedAction implements PrivilegedAction<Thread> {
private static AtomicInteger count = new AtomicInteger(0);
private final Runnable r;
public NewThreadPrivilegedAction(Runnable r) {
this.r = r;
}
@Override
public Thread run() {
Thread t = new Thread(r);
t.setName("WebSocketClient-AsyncIO-" + count.incrementAndGet());
t.setContextClassLoader(this.getClass().getClassLoader());
t.setDaemon(true);
return t;
}
private static void load() {
// NO-OP. Just provides a hook to enable the class to be loaded
}
}
}
}
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