forked from cwensel/cascading
/
ShutdownUtil.java
128 lines (106 loc) · 3.11 KB
/
ShutdownUtil.java
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/*
* Copyright (c) 2007-2015 Concurrent, Inc. All Rights Reserved.
*
* Project and contact information: http://www.cascading.org/
*
* This file is part of the Cascading 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 cascading.util;
import java.util.Comparator;
import java.util.Queue;
import java.util.concurrent.PriorityBlockingQueue;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* ShutdownUtil is a private helper class for registering dependent shutdown hooks to maintain internal state
* information reliably when a jvm is shutting down.
* <p/>
* This api is not intended for public use.
*/
public class ShutdownUtil
{
private static final Logger LOG = LoggerFactory.getLogger( ShutdownUtil.class );
public static abstract class Hook
{
public enum Priority
{
FIRST, WORK_PARENT, WORK_CHILD, SERVICE_CONSUMER, SERVICE_PROVIDER, LAST
}
public abstract Priority priority();
public abstract void execute();
}
private static Queue<Hook> queue = new PriorityBlockingQueue<Hook>( 20, new Comparator<Hook>()
{
@Override
public int compare( Hook lhs, Hook rhs )
{
if( lhs == rhs )
return 0;
if( lhs == null )
return -1;
else if( rhs == null )
return 1;
return lhs.priority().compareTo( rhs.priority() );
}
}
);
private static Thread shutdownHook;
public static void addHook( Hook hook )
{
if( hook == null )
throw new IllegalArgumentException( "hook may not be null" );
registerShutdownHook();
queue.add( hook );
}
public static boolean removeHook( Hook hook )
{
return queue.remove( hook );
}
public static synchronized void registerShutdownHook()
{
if( shutdownHook != null )
return;
shutdownHook = new Thread( "cascading shutdown hooks" )
{
@Override
public void run()
{
// These are not threads, so each one will be run in priority order
// blocking until the previous is complete
while( !queue.isEmpty() )
{
Hook hook = null;
try
{
hook = queue.poll();
// may get removed while shutdown is executing
if( hook == null )
continue;
hook.execute();
}
catch( Exception exception )
{
LOG.error( "failed executing hook: {}, with exception: {}", hook, exception );
}
}
}
};
Runtime.getRuntime().addShutdownHook( shutdownHook );
}
public static void deregisterShutdownHook()
{
Runtime.getRuntime().removeShutdownHook( shutdownHook );
}
}