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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.concurrent;
import com.yahoo.yolean.Exceptions;
import java.time.Duration;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Executor that serializes runnables with the same key, but may parallelize over different keys.
*
* @author jonmv
*/
public class StripedExecutor<Key> {
private static final Logger logger = Logger.getLogger(StripedExecutor.class.getName());
private final Map<Key, Deque<Runnable>> commands = new HashMap<>();
private final ExecutorService executor;
/** Creates a new StripedExecutor which delegates to a {@link Executors#newCachedThreadPool(ThreadFactory)}. */
public StripedExecutor() {
this(Executors.newCachedThreadPool(ThreadFactoryFactory.getDaemonThreadFactory(StripedExecutor.class.getSimpleName())));
}
/** Creates a new StripedExecutor which delegates to the given executor service. */
public StripedExecutor(ExecutorService executor) {
this.executor = executor;
}
/**
* Executes the given command. If other commands are already running or queued for the given key,
* execution of this command happens after those, on the same thread as is running them.
* <p>
* Any exception thrown by the command will only be logged, to allow subsequent commands to run.
*/
public void execute(Key key, Runnable command) {
synchronized (commands) {
if (null == commands.putIfAbsent(key, new ArrayDeque<>(List.of(command))))
executor.execute(() -> runAll(key));
else
commands.get(key).add(command);
}
}
/** Runs all submitted commands for the given key, then removes the queue for the key and returns. */
private void runAll(Key key) {
while (true) {
Runnable command;
synchronized (commands) {
command = commands.containsKey(key) ? commands.get(key).poll() : null;
if (command == null) {
commands.remove(key);
break;
}
}
try {
command.run();
}
catch (RuntimeException e) {
logger.log(Level.WARNING, e, () -> "Exception caught: " + Exceptions.toMessageString(e));
}
}
}
/** Shuts down the delegate executor and waits for it to terminate. */
public void shutdownAndWait() {
shutdownAndWait(Duration.ofSeconds(30), Duration.ofSeconds(10));
}
/**
* Shuts down the delegate executor and waits for the given grace duration for it to terminate.
* If this fails, tells the executor to {@link ExecutorService#shutdownNow()}), and waits for the die duration.
*/
public void shutdownAndWait(Duration grace, Duration die) {
executor.shutdown();
try {
executor.awaitTermination(grace.toMillis(), TimeUnit.MILLISECONDS);
}
catch (InterruptedException e) {
logger.log(Level.INFO, "Interrupted waiting for executor to complete", e);
}
if ( ! executor.isTerminated()) {
executor.shutdownNow();
try {
executor.awaitTermination(die.toMillis(), TimeUnit.MILLISECONDS);
}
catch (InterruptedException e) {
logger.log(Level.WARNING, "Interrupted waiting for executor to die", e);
}
if ( ! executor.isTerminated())
throw new RuntimeException("Failed to shut down executor");
}
}
}
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