/*
* Copyright (c) 2008-2017, Hazelcast, Inc. All Rights Reserved.
*
* 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 com.hazelcast.util.executor;
import com.hazelcast.instance.OutOfMemoryErrorDispatcher;
import com.hazelcast.internal.util.counters.SwCounter;
import com.hazelcast.logging.ILogger;
import java.util.Random;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Executor;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import static com.hazelcast.util.HashUtil.hashToIndex;
import static com.hazelcast.util.Preconditions.checkPositive;
import static java.lang.Math.ceil;
/**
* The StripedExecutor internally uses a stripe of queues and each queue has its own private worker-thread.
* When a task is 'executed' on the StripedExecutor, the task is checked if it is a StripedRunnable. If it
* is, the right worker is looked up and the task put in the queue of that worker. If the task is not a
* StripedRunnable, a random worker is looked up.
*
* If the queue is full and the runnable implements TimeoutRunnable, then a configurable amount of blocking is
* done on the queue. If the runnable doesn't implement TimeoutRunnable or when the blocking times out,
* then the task is rejected and a RejectedExecutionException is thrown.
*/
public final class StripedExecutor implements Executor {
public static final AtomicLong THREAD_ID_GENERATOR = new AtomicLong();
private final int size;
private final ILogger logger;
private final Worker[] workers;
private final Random rand = new Random();
private volatile boolean live = true;
public StripedExecutor(ILogger logger, String threadNamePrefix, int threadCount, int maximumQueueCapacity) {
checkPositive(threadCount, "threadCount should be positive but found " + threadCount);
checkPositive(maximumQueueCapacity, "maximumQueueCapacity should be positive but found " + maximumQueueCapacity);
this.logger = logger;
this.size = threadCount;
this.workers = new Worker[threadCount];
// `maximumQueueCapacity` is the given max capacity for this executor. Each worker in this executor should consume
// only a portion of that capacity. Otherwise we will have `threadCount * maximumQueueCapacity` instead of
// `maximumQueueCapacity`.
final int perThreadMaxQueueCapacity = (int) ceil(1D * maximumQueueCapacity / threadCount);
for (int i = 0; i < threadCount; i++) {
Worker worker = new Worker(threadNamePrefix, perThreadMaxQueueCapacity);
worker.start();
workers[i] = worker;
}
}
/**
* Returns the total number of tasks pending to be executed.
*
* @return total work queue size.
*/
public int getWorkQueueSize() {
int size = 0;
for (Worker worker : workers) {
size += worker.workQueue.size();
}
return size;
}
/**
* Returns the total number of processed events.
*
* @return
*/
public long processedCount() {
long size = 0;
for (Worker worker : workers) {
size += worker.processed.inc();
}
return size;
}
/**
* Shuts down this StripedExecutor.
* <p/>
* No checking is done to see if the StripedExecutor already is shut down, so it should be called only once.
* <p/>
* If there is any pending work, it will be thrown away.
*/
public void shutdown() {
live = false;
for (Worker worker : workers) {
worker.workQueue.clear();
worker.interrupt();
}
}
/**
* Checks if this StripedExecutor is alive (so not shut down).
*
* @return live (true)
*/
public boolean isLive() {
return live;
}
@Override
public void execute(Runnable command) {
if (command == null) {
throw new NullPointerException("command can't be null");
}
if (!live) {
throw new RejectedExecutionException("Executor is terminated!");
}
Worker worker = getWorker(command);
worker.schedule(command);
}
private Worker getWorker(Runnable command) {
final int key;
if (command instanceof StripedRunnable) {
key = ((StripedRunnable) command).getKey();
} else {
key = rand.nextInt();
}
int index = hashToIndex(key, size);
return workers[index];
}
// used in tests.
Worker[] getWorkers() {
return workers;
}
final class Worker extends Thread {
private final BlockingQueue<Runnable> workQueue;
private final SwCounter processed = SwCounter.newSwCounter();
private final int queueCapacity;
private Worker(String threadNamePrefix, int queueCapacity) {
super(threadNamePrefix + "-" + THREAD_ID_GENERATOR.incrementAndGet());
this.workQueue = new LinkedBlockingQueue<Runnable>(queueCapacity);
this.queueCapacity = queueCapacity;
}
private void schedule(Runnable command) {
long timeout = 0;
TimeUnit timeUnit = TimeUnit.SECONDS;
if (command instanceof TimeoutRunnable) {
TimeoutRunnable timeoutRunnable = ((TimeoutRunnable) command);
timeout = timeoutRunnable.getTimeout();
timeUnit = timeoutRunnable.getTimeUnit();
}
boolean offered;
try {
if (timeout == 0) {
offered = workQueue.offer(command);
} else {
offered = workQueue.offer(command, timeout, timeUnit);
}
} catch (InterruptedException e) {
throw new RejectedExecutionException("Thread is interrupted while offering work");
}
if (!offered) {
throw new RejectedExecutionException("Task: " + command + " is rejected, the worker queue is full!");
}
}
@Override
public void run() {
for (; ; ) {
try {
try {
Runnable task = workQueue.take();
process(task);
} catch (InterruptedException e) {
if (!live) {
return;
}
}
} catch (Throwable t) {
//This should not happen because the process method is protected against failure.
//So if this happens, something very seriously is going wrong.
logger.severe(getName() + " caught an exception", t);
}
}
}
private void process(Runnable task) {
processed.inc();
try {
task.run();
} catch (Throwable e) {
OutOfMemoryErrorDispatcher.inspectOutOfMemoryError(e);
logger.severe(getName() + " caught an exception while processing task:" + task, e);
}
}
// used in tests.
int getQueueCapacity() {
return queueCapacity;
}
}
}