PhasingExecutor.java
/*
* 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.
*/
package org.apache.maven.impl.util;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* The phasing executor allows executing tasks in parallel and waiting for all tasks
* to be executed before fully closing the executor. Tasks can be submitted even after
* the close method has been called, allowing for use with try-with-resources.
* The {@link #phase()} method can be used to submit tasks and wait for them to be
* executed without closing the executor.
*
* <p>Example usage:
* <pre>
* try (PhasingExecutor executor = createExecutor()) {
* try (var phase = executor.phase()) {
* executor.execute(() -> { /* task 1 */ });
* executor.execute(() -> { /* task 2 */ });
* More tasks...
* } This will wait for all tasks in this phase to complete
*
* You can have multiple phases
* try (var anotherPhase = executor.phase()) {
* executor.execute(() -> { /* another task */ });
* }
* } The executor will wait for all tasks to complete before shutting down
* </pre>
*/
public class PhasingExecutor implements Executor, AutoCloseable {
private static final AtomicInteger ID = new AtomicInteger(0);
private static final Logger LOGGER = LoggerFactory.getLogger(PhasingExecutor.class);
private final ExecutorService executor;
private final AtomicBoolean shutdownInitiated = new AtomicBoolean(false);
private final AtomicBoolean inPhase = new AtomicBoolean(false);
private final AtomicInteger activeTaskCount = new AtomicInteger(0);
private final AtomicInteger completedTaskCount = new AtomicInteger(0);
private final int id = ID.incrementAndGet();
private final ReentrantLock lock = new ReentrantLock();
private final Condition taskCompletionCondition = lock.newCondition();
public PhasingExecutor(ExecutorService executor) {
this.executor = executor;
log("[{}][general] PhasingExecutor created.");
}
@Override
public void execute(Runnable command) {
activeTaskCount.incrementAndGet();
log("[{}][task] Task submitted. Active tasks: {}", activeTaskCount.get());
executor.execute(() -> {
try {
log("[{}][task] Task executing. Active tasks: {}", activeTaskCount.get());
command.run();
} finally {
lock.lock();
try {
completedTaskCount.incrementAndGet();
activeTaskCount.decrementAndGet();
log("[{}][task] Task completed. Active tasks: {}", activeTaskCount.get());
taskCompletionCondition.signalAll();
if (activeTaskCount.get() == 0 && shutdownInitiated.get()) {
log("[{}][task] Last task completed. Initiating executor shutdown.");
executor.shutdown();
}
} finally {
lock.unlock();
}
}
});
}
public AutoCloseable phase() {
if (inPhase.getAndSet(true)) {
throw new IllegalStateException("Already in a phase");
}
int phaseNumber = completedTaskCount.get();
log("[{}][phase] Entering phase {}. Active tasks: {}", phaseNumber, activeTaskCount.get());
return () -> {
try {
int tasksAtPhaseStart = completedTaskCount.get();
log("[{}][phase] Closing phase {}. Waiting for all tasks to complete.", phaseNumber);
lock.lock();
try {
while (activeTaskCount.get() > 0
&& completedTaskCount.get() - tasksAtPhaseStart < activeTaskCount.get()) {
taskCompletionCondition.await(100, TimeUnit.MILLISECONDS);
}
} finally {
lock.unlock();
}
log("[{}][phase] Phase {} completed. Total completed tasks: {}", phaseNumber, completedTaskCount.get());
} catch (InterruptedException e) {
log("[{}][phase] Phase {} was interrupted.", phaseNumber);
Thread.currentThread().interrupt();
throw new RuntimeException("Phase interrupted", e);
} finally {
inPhase.set(false);
}
};
}
@Override
public void close() {
log("[{}][close] Closing PhasingExecutor. Active tasks: {}", activeTaskCount.get());
if (shutdownInitiated.getAndSet(true)) {
log("[{}][close] Shutdown already initiated. Returning.");
return;
}
lock.lock();
try {
while (activeTaskCount.get() > 0) {
log("[{}][close] Waiting for {} active tasks to complete.", activeTaskCount.get());
taskCompletionCondition.await(100, TimeUnit.MILLISECONDS);
}
} catch (InterruptedException e) {
log("[{}][close] Interrupted while waiting for tasks to complete.");
Thread.currentThread().interrupt();
} finally {
lock.unlock();
log("[{}][close] All tasks completed. Shutting down executor.");
executor.shutdown();
}
log("[{}][close] PhasingExecutor closed. Total completed tasks: {}", completedTaskCount.get());
}
private void log(String message) {
LOGGER.debug(message, id);
}
private void log(String message, Object o1) {
LOGGER.debug(message, id, o1);
}
private void log(String message, Object o1, Object o2) {
LOGGER.debug(message, id, o1, o2);
}
}