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// Copyright (C) 2009 The Android Open Source Project
//
// Licensed 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 com.google.gerrit.pgm.util;
import java.util.ArrayList;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class RuntimeShutdown {
private static final ShutdownCallback cb = new ShutdownCallback();
/** Add a task to be performed when graceful shutdown is requested. */
public static void add(final Runnable task) {
if (!cb.add(task)) {
// If the shutdown has already begun we cannot enqueue a new
// task. Instead trigger the task in the caller, without any
// of our locks held.
//
task.run();
}
}
/** Wait for the JVM shutdown to occur. */
public static void waitFor() {
cb.waitForShutdown();
}
public static void manualShutdown() {
cb.manualShutdown();
}
private RuntimeShutdown() {}
private static class ShutdownCallback extends Thread {
private static final Logger log = LoggerFactory.getLogger(ShutdownCallback.class);
private final List<Runnable> tasks = new ArrayList<>();
private boolean shutdownStarted;
private boolean shutdownComplete;
ShutdownCallback() {
setName("ShutdownCallback");
}
boolean add(final Runnable newTask) {
synchronized (this) {
if (!shutdownStarted && !shutdownComplete) {
if (tasks.isEmpty()) {
Runtime.getRuntime().addShutdownHook(this);
}
tasks.add(newTask);
return true;
}
// We don't permit adding a task once shutdown has started.
//
return false;
}
}
@Override
public void run() {
log.debug("Graceful shutdown requested");
List<Runnable> taskList;
synchronized (this) {
shutdownStarted = true;
taskList = tasks;
}
for (Runnable task : taskList) {
try {
task.run();
} catch (Exception err) {
log.error("Cleanup task failed", err);
}
}
log.debug("Shutdown complete");
synchronized (this) {
shutdownComplete = true;
notifyAll();
}
}
void manualShutdown() {
Runtime.getRuntime().removeShutdownHook(this);
run();
}
void waitForShutdown() {
synchronized (this) {
while (!shutdownComplete) {
try {
wait();
} catch (InterruptedException e) {
return;
}
}
}
}
}
}
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