org.apache.flink.runtime.util.JvmShutdownSafeguard Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* distributed with this work for additional information
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* 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.flink.runtime.util;
import org.slf4j.Logger;
import static org.apache.flink.util.Preconditions.checkArgument;
/**
* A utility that guards against blocking shutdown hooks that block JVM shutdown.
*
* When the JVM shuts down cleanly (SIGTERM or {@link System#exit(int)}) it runs
* all installed shutdown hooks. It is possible that any of the shutdown hooks blocks,
* which causes the JVM to get stuck and not exit at all.
*
*
This utility installs a shutdown hook that forcibly terminates the JVM if it is still alive
* a certain time after clean shutdown was initiated. Even if some shutdown hooks block, the JVM will
* terminate within a certain time.
*/
public class JvmShutdownSafeguard extends Thread {
/** Default delay to wait after clean shutdown was stared, before forcibly terminating the JVM */
private static final long DEFAULT_DELAY = 5000L;
/** The exit code returned by the JVM process if it is killed by the safeguard */
private static final int EXIT_CODE = -17;
/** The thread that actually does the termination */
private final Thread terminator;
private JvmShutdownSafeguard(long delayMillis) {
setName("JVM Terminator Launcher");
this.terminator = new Thread(new DelayedTerminator(delayMillis), "Jvm Terminator");
this.terminator.setDaemon(true);
}
@Override
public void run() {
// Because this thread is registered as a shutdown hook, we cannot
// wait here and then call for termination. That would always delay the JVM shutdown.
// Instead, we spawn a non shutdown hook thread from here.
// That thread is a daemon, so it does not keep the JVM alive.
terminator.start();
}
// ------------------------------------------------------------------------
// The actual Shutdown thread
// ------------------------------------------------------------------------
private static class DelayedTerminator implements Runnable {
private final long delayMillis;
private DelayedTerminator(long delayMillis) {
this.delayMillis = delayMillis;
}
@Override
public void run() {
try {
Thread.sleep(delayMillis);
}
catch (Throwable t) {
// catch all, including thread death, etc
}
Runtime.getRuntime().halt(EXIT_CODE);
}
}
// ------------------------------------------------------------------------
// Installing as a shutdown hook
// ------------------------------------------------------------------------
/**
* Installs the safeguard shutdown hook. The maximum time that the JVM is allowed to spend
* on shutdown before being killed is five seconds.
*
* @param logger The logger to log errors to.
*/
public static void installAsShutdownHook(Logger logger) {
installAsShutdownHook(logger, DEFAULT_DELAY);
}
/**
* Installs the safeguard shutdown hook. The maximum time that the JVM is allowed to spend
* on shutdown before being killed is the given number of milliseconds.
*
* @param logger The logger to log errors to.
* @param delayMillis The delay (in milliseconds) to wait after clean shutdown was stared,
* before forcibly terminating the JVM.
*/
public static void installAsShutdownHook(Logger logger, long delayMillis) {
checkArgument(delayMillis >= 0, "delay must be >= 0");
// install the blocking shutdown hook
Thread shutdownHook = new JvmShutdownSafeguard(delayMillis);
try {
// Add JVM shutdown hook to call shutdown of service
Runtime.getRuntime().addShutdownHook(shutdownHook);
}
catch (IllegalStateException ignored) {
// JVM is already shutting down. No need to do this.
}
catch (Throwable t) {
logger.error("Cannot install JVM Shutdown Safeguard against blocked shutdown hooks");
}
}
}