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LockingEventSpy.java
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LockingEventSpy.java
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package org.apache.maven.execution;
/*
* 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.
*/
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import javax.inject.Named;
import javax.inject.Singleton;
import org.apache.maven.eventspy.AbstractEventSpy;
import org.apache.maven.eventspy.EventSpy;
import org.apache.maven.project.MavenProject;
import org.eclipse.aether.SessionData;
import org.eclipse.sisu.Typed;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* EventSpy implementation that provides a per-project locking mechanism
* to make sure a given project can not be built concurrently.
* This case can happen when running parallel builds with forked lifecycles.
*/
@Singleton
@Named
@Typed( EventSpy.class )
public class LockingEventSpy extends AbstractEventSpy
{
private static final Object LOCKS_KEY = new Object();
private final Logger logger = LoggerFactory.getLogger( getClass() );
@Override
public void onEvent( Object event ) throws Exception
{
if ( event instanceof ExecutionEvent )
{
ExecutionEvent executionEvent = ( ExecutionEvent ) event;
switch ( executionEvent.getType() )
{
case ProjectStarted:
case ForkedProjectStarted:
Lock lock = getLock( executionEvent );
if ( !lock.tryLock() )
{
logger.debug( "Suspending concurrent execution of project '{}'", executionEvent.getProject() );
lock.lockInterruptibly();
logger.debug( "Resuming execution of project '{}'", executionEvent.getProject() );
}
break;
case ProjectSucceeded:
case ProjectFailed:
case ForkedProjectSucceeded:
case ForkedProjectFailed:
getLock( executionEvent ).unlock();
break;
default:
break;
}
}
}
@SuppressWarnings( { "unchecked", "rawtypes" } )
private Lock getLock( ExecutionEvent event )
{
SessionData data = event.getSession().getRepositorySession().getData();
Map<MavenProject, Lock> locks = ( Map ) data.get( LOCKS_KEY );
// initialize the value if not already done (in case of a concurrent access) to the method
if ( locks == null )
{
// the call to data.set(k, null, v) is effectively a call to data.putIfAbsent(k, v)
data.set( LOCKS_KEY, null, new ConcurrentHashMap<>() );
locks = ( Map ) data.get( LOCKS_KEY );
}
return locks.computeIfAbsent( event.getProject(), p -> new ReentrantLock() );
}
}