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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.util.HashSet;
import java.util.Set;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.ExceptionUtils;
import org.apache.tomcat.util.res.StringManager;
/**
* Provides a background processing mechanism that triggers roughly once a
* second. The class maintains a thread that only runs when there is at least
* one instance of {@link BackgroundProcess} registered.
*/
public class BackgroundProcessManager {
private static final Log log =
LogFactory.getLog(BackgroundProcessManager.class);
private static final StringManager sm =
StringManager.getManager(Constants.PACKAGE_NAME);
private static final BackgroundProcessManager instance;
static {
instance = new BackgroundProcessManager();
}
public static BackgroundProcessManager getInstance() {
return instance;
}
private final Set<BackgroundProcess> processes = new HashSet<>();
private final Object processesLock = new Object();
private WsBackgroundThread wsBackgroundThread = null;
private BackgroundProcessManager() {
// Hide default constructor
}
public void register(BackgroundProcess process) {
synchronized (processesLock) {
if (processes.size() == 0) {
wsBackgroundThread = new WsBackgroundThread(this);
wsBackgroundThread.setContextClassLoader(
this.getClass().getClassLoader());
wsBackgroundThread.setDaemon(true);
wsBackgroundThread.start();
}
processes.add(process);
}
}
public void unregister(BackgroundProcess process) {
synchronized (processesLock) {
processes.remove(process);
if (wsBackgroundThread != null && processes.size() == 0) {
wsBackgroundThread.halt();
wsBackgroundThread = null;
}
}
}
private void process() {
Set<BackgroundProcess> currentProcesses = new HashSet<>();
synchronized (processesLock) {
currentProcesses.addAll(processes);
}
for (BackgroundProcess process : currentProcesses) {
try {
process.backgroundProcess();
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
log.error(sm.getString(
"backgroundProcessManager.processFailed"), t);
}
}
}
private static class WsBackgroundThread extends Thread {
private final BackgroundProcessManager manager;
private volatile boolean running = true;
public WsBackgroundThread(BackgroundProcessManager manager) {
setName("WebSocket background processing");
this.manager = manager;
}
@Override
public void run() {
while (running) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// Ignore
}
manager.process();
}
}
public void halt() {
setName("WebSocket background processing - stopping");
running = false;
}
}
}
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