michael-o commented on a change in pull request #476: URL: https://github.com/apache/maven/pull/476#discussion_r734995702
########## File path: maven-core/src/main/java/org/apache/maven/execution/LockingEventSpy.java ########## @@ -0,0 +1,98 @@ +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 ) Review comment: Would it make sense to use `SessionData#computeIfAbsent()` if we release Resolver and integrate? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
