[GitHub] [maven] MartinKanters commented on a change in pull request #476: [MNG-7156] Parallel build can cause issues between clean and forked g…

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MartinKanters commented on a change in pull request #476:
URL: https://github.com/apache/maven/pull/476#discussion_r646170192



##########
File path: maven-core/src/main/java/org/apache/maven/execution/LockingEventSpy.java
##########
@@ -0,0 +1,96 @@
+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 build twice concurrently.

Review comment:
       ```suggestion
    * to make sure a given project can not be built concurrently.
   ```

##########
File path: maven-core/src/main/java/org/apache/maven/execution/LockingEventSpy.java
##########
@@ -0,0 +1,96 @@
+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 build twice concurrently.
+ * This case can happen when running parallel builds with forked lifecycles.
+ */
+@Singleton
+@Named
+@Typed( EventSpy.class )
+public class LockingEventSpy extends AbstractEventSpy
+{
+
+    private final Logger logger = LoggerFactory.getLogger( getClass() );
+
+    private static final Object LOCKS_KEY = new Object();
+
+    @SuppressWarnings( { "unchecked", "rawtypes" } )
+    private Lock getLock( ExecutionEvent event )
+    {
+        SessionData data = event.getSession().getRepositorySession().getData();
+        Map<MavenProject, Lock> locks = ( Map ) data.get( LOCKS_KEY );
+        if ( locks == null )
+        {
+            data.set( LOCKS_KEY, null, new ConcurrentHashMap<>() );
+            locks = ( Map ) data.get( LOCKS_KEY );
+        }
+        return locks.computeIfAbsent( event.getProject(), p -> new ReentrantLock() );
+    }
+
+    @Override
+    public void onEvent( Object event ) throws Exception
+    {
+        if ( event instanceof ExecutionEvent )
+        {
+            ExecutionEvent ee = ( ExecutionEvent ) event;

Review comment:
       Can we come up with a more descriptive name than this? Perhaps just `executionEvent`?

##########
File path: maven-core/src/main/java/org/apache/maven/execution/LockingEventSpy.java
##########
@@ -0,0 +1,96 @@
+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 build twice concurrently.
+ * This case can happen when running parallel builds with forked lifecycles.
+ */
+@Singleton
+@Named
+@Typed( EventSpy.class )
+public class LockingEventSpy extends AbstractEventSpy

Review comment:
       I think it's quite an elegant solution, but I'm not sure if using an `EventSpy` for this purpose is how it should be done in `maven-core`. I don't think there are other implementations of it in core. 

##########
File path: maven-core/src/main/java/org/apache/maven/execution/LockingEventSpy.java
##########
@@ -0,0 +1,96 @@
+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 build twice concurrently.
+ * This case can happen when running parallel builds with forked lifecycles.
+ */
+@Singleton
+@Named
+@Typed( EventSpy.class )
+public class LockingEventSpy extends AbstractEventSpy
+{
+
+    private final Logger logger = LoggerFactory.getLogger( getClass() );
+
+    private static final Object LOCKS_KEY = new Object();
+
+    @SuppressWarnings( { "unchecked", "rawtypes" } )
+    private Lock getLock( ExecutionEvent event )
+    {
+        SessionData data = event.getSession().getRepositorySession().getData();
+        Map<MavenProject, Lock> locks = ( Map ) data.get( LOCKS_KEY );
+        if ( locks == null )
+        {
+            data.set( LOCKS_KEY, null, new ConcurrentHashMap<>() );
+            locks = ( Map ) data.get( LOCKS_KEY );
+        }
+        return locks.computeIfAbsent( event.getProject(), p -> new ReentrantLock() );
+    }
+
+    @Override
+    public void onEvent( Object event ) throws Exception
+    {
+        if ( event instanceof ExecutionEvent )
+        {
+            ExecutionEvent ee = ( ExecutionEvent ) event;
+            switch ( ee.getType() )
+            {
+            case ProjectStarted:
+            case ForkedProjectStarted:
+                Lock lock = getLock( ee );
+                if ( !lock.tryLock() )
+                {
+                    logger.warn( "Suspending concurrent execution of project " + ee.getProject() );
+                    getLock( ee ).lockInterruptibly();
+                    logger.warn( "Resuming execution of project " + ee.getProject() );
+                }
+                break;
+            case ProjectSucceeded:
+            case ProjectFailed:

Review comment:
       I think we might be missing ProjectSkipped right now, did your leave this out on purpose?

##########
File path: maven-core/src/main/java/org/apache/maven/execution/LockingEventSpy.java
##########
@@ -0,0 +1,96 @@
+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 build twice concurrently.
+ * This case can happen when running parallel builds with forked lifecycles.
+ */
+@Singleton
+@Named
+@Typed( EventSpy.class )
+public class LockingEventSpy extends AbstractEventSpy
+{
+
+    private final Logger logger = LoggerFactory.getLogger( getClass() );
+
+    private static final Object LOCKS_KEY = new Object();
+
+    @SuppressWarnings( { "unchecked", "rawtypes" } )
+    private Lock getLock( ExecutionEvent event )
+    {
+        SessionData data = event.getSession().getRepositorySession().getData();
+        Map<MavenProject, Lock> locks = ( Map ) data.get( LOCKS_KEY );
+        if ( locks == null )
+        {
+            data.set( LOCKS_KEY, null, new ConcurrentHashMap<>() );
+            locks = ( Map ) data.get( LOCKS_KEY );
+        }
+        return locks.computeIfAbsent( event.getProject(), p -> new ReentrantLock() );
+    }
+
+    @Override
+    public void onEvent( Object event ) throws Exception
+    {
+        if ( event instanceof ExecutionEvent )
+        {
+            ExecutionEvent ee = ( ExecutionEvent ) event;
+            switch ( ee.getType() )
+            {
+            case ProjectStarted:
+            case ForkedProjectStarted:
+                Lock lock = getLock( ee );
+                if ( !lock.tryLock() )
+                {
+                    logger.warn( "Suspending concurrent execution of project " + ee.getProject() );
+                    getLock( ee ).lockInterruptibly();
+                    logger.warn( "Resuming execution of project " + ee.getProject() );

Review comment:
       ```suggestion
                       logger.warn( "Suspending concurrent execution of project '{}'", ee.getProject() );
                       getLock( ee ).lockInterruptibly();
                       logger.warn( "Resuming execution of project '{}'", ee.getProject() );
   ```




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