Merge pull request #421 from gnodet/i419

Fix concurrent build of projects when using forked lifecycles

daemon/src/main/java/org/mvndaemon/mvnd/execution/LockingEventSpy.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * 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 org.mvndaemon.mvnd.execution;
+
+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.execution.ExecutionEvent;
+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:
+            case ForkedProjectSucceeded:
+            case ForkedProjectFailed:
+                getLock(ee).unlock();
+                break;
+            }
+        }
+    }
+
+}