/*
* 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 final Log log = LogFactory.getLog(BackgroundProcessManager.class);
private static final StringManager sm = StringManager.getManager(BackgroundProcessManager.class);
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.isEmpty()) {
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.isEmpty()) {
wsBackgroundThread.halt();
wsBackgroundThread = null;
}
}
}
private void process() {
Set<BackgroundProcess> currentProcesses;
synchronized (processesLock) {
currentProcesses = new HashSet<>(processes);
}
for (BackgroundProcess process : currentProcesses) {
try {
process.backgroundProcess();
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
log.error(sm.getString("backgroundProcessManager.processFailed"), t);
}
}
}
/*
* For unit testing.
*/
int getProcessCount() {
synchronized (processesLock) {
return processes.size();
}
}
void shutdown() {
synchronized (processesLock) {
processes.clear();
if (wsBackgroundThread != null) {
wsBackgroundThread.halt();
wsBackgroundThread = null;
}
}
}
private static class WsBackgroundThread extends Thread {
private final BackgroundProcessManager manager;
private volatile boolean running = true;
WsBackgroundThread(BackgroundProcessManager manager) {
setName("WebSocket background processing");
this.manager = manager;
}
@Override
public void run() {
while (running) {
try {
sleep(1000);
} catch (InterruptedException e) {
// Ignore
}
manager.process();
}
}
public void halt() {
setName("WebSocket background processing - stopping");
running = false;
}
}
}