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Reactive Extensions for Java
/**
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex.internal.schedulers;
import io.reactivex.Scheduler;
import io.reactivex.annotations.NonNull;
import io.reactivex.disposables.*;
import io.reactivex.internal.disposables.EmptyDisposable;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
/**
* Scheduler that creates and caches a set of thread pools and reuses them if possible.
*/
public final class IoScheduler extends Scheduler {
private static final String WORKER_THREAD_NAME_PREFIX = "RxCachedThreadScheduler";
static final RxThreadFactory WORKER_THREAD_FACTORY;
private static final String EVICTOR_THREAD_NAME_PREFIX = "RxCachedWorkerPoolEvictor";
static final RxThreadFactory EVICTOR_THREAD_FACTORY;
/** The name of the system property for setting the keep-alive time (in seconds) for this Scheduler workers. */
private static final String KEY_KEEP_ALIVE_TIME = "rx2.io-keep-alive-time";
public static final long KEEP_ALIVE_TIME_DEFAULT = 60;
private static final long KEEP_ALIVE_TIME;
private static final TimeUnit KEEP_ALIVE_UNIT = TimeUnit.SECONDS;
static final ThreadWorker SHUTDOWN_THREAD_WORKER;
final ThreadFactory threadFactory;
final AtomicReference pool;
/** The name of the system property for setting the thread priority for this Scheduler. */
private static final String KEY_IO_PRIORITY = "rx2.io-priority";
static final CachedWorkerPool NONE;
static {
KEEP_ALIVE_TIME = Long.getLong(KEY_KEEP_ALIVE_TIME, KEEP_ALIVE_TIME_DEFAULT);
SHUTDOWN_THREAD_WORKER = new ThreadWorker(new RxThreadFactory("RxCachedThreadSchedulerShutdown"));
SHUTDOWN_THREAD_WORKER.dispose();
int priority = Math.max(Thread.MIN_PRIORITY, Math.min(Thread.MAX_PRIORITY,
Integer.getInteger(KEY_IO_PRIORITY, Thread.NORM_PRIORITY)));
WORKER_THREAD_FACTORY = new RxThreadFactory(WORKER_THREAD_NAME_PREFIX, priority);
EVICTOR_THREAD_FACTORY = new RxThreadFactory(EVICTOR_THREAD_NAME_PREFIX, priority);
NONE = new CachedWorkerPool(0, null, WORKER_THREAD_FACTORY);
NONE.shutdown();
}
static final class CachedWorkerPool implements Runnable {
private final long keepAliveTime;
private final ConcurrentLinkedQueue expiringWorkerQueue;
final CompositeDisposable allWorkers;
private final ScheduledExecutorService evictorService;
private final Future evictorTask;
private final ThreadFactory threadFactory;
CachedWorkerPool(long keepAliveTime, TimeUnit unit, ThreadFactory threadFactory) {
this.keepAliveTime = unit != null ? unit.toNanos(keepAliveTime) : 0L;
this.expiringWorkerQueue = new ConcurrentLinkedQueue();
this.allWorkers = new CompositeDisposable();
this.threadFactory = threadFactory;
ScheduledExecutorService evictor = null;
Future task = null;
if (unit != null) {
evictor = Executors.newScheduledThreadPool(1, EVICTOR_THREAD_FACTORY);
task = evictor.scheduleWithFixedDelay(this, this.keepAliveTime, this.keepAliveTime, TimeUnit.NANOSECONDS);
}
evictorService = evictor;
evictorTask = task;
}
@Override
public void run() {
evictExpiredWorkers();
}
ThreadWorker get() {
if (allWorkers.isDisposed()) {
return SHUTDOWN_THREAD_WORKER;
}
while (!expiringWorkerQueue.isEmpty()) {
ThreadWorker threadWorker = expiringWorkerQueue.poll();
if (threadWorker != null) {
return threadWorker;
}
}
// No cached worker found, so create a new one.
ThreadWorker w = new ThreadWorker(threadFactory);
allWorkers.add(w);
return w;
}
void release(ThreadWorker threadWorker) {
// Refresh expire time before putting worker back in pool
threadWorker.setExpirationTime(now() + keepAliveTime);
expiringWorkerQueue.offer(threadWorker);
}
void evictExpiredWorkers() {
if (!expiringWorkerQueue.isEmpty()) {
long currentTimestamp = now();
for (ThreadWorker threadWorker : expiringWorkerQueue) {
if (threadWorker.getExpirationTime() <= currentTimestamp) {
if (expiringWorkerQueue.remove(threadWorker)) {
allWorkers.remove(threadWorker);
}
} else {
// Queue is ordered with the worker that will expire first in the beginning, so when we
// find a non-expired worker we can stop evicting.
break;
}
}
}
}
long now() {
return System.nanoTime();
}
void shutdown() {
allWorkers.dispose();
if (evictorTask != null) {
evictorTask.cancel(true);
}
if (evictorService != null) {
evictorService.shutdownNow();
}
}
}
public IoScheduler() {
this(WORKER_THREAD_FACTORY);
}
/**
* Constructs an IoScheduler with the given thread factory and starts the pool of workers.
* @param threadFactory thread factory to use for creating worker threads. Note that this takes precedence over any
* system properties for configuring new thread creation. Cannot be null.
*/
public IoScheduler(ThreadFactory threadFactory) {
this.threadFactory = threadFactory;
this.pool = new AtomicReference(NONE);
start();
}
@Override
public void start() {
CachedWorkerPool update = new CachedWorkerPool(KEEP_ALIVE_TIME, KEEP_ALIVE_UNIT, threadFactory);
if (!pool.compareAndSet(NONE, update)) {
update.shutdown();
}
}
@Override
public void shutdown() {
for (;;) {
CachedWorkerPool curr = pool.get();
if (curr == NONE) {
return;
}
if (pool.compareAndSet(curr, NONE)) {
curr.shutdown();
return;
}
}
}
@NonNull
@Override
public Worker createWorker() {
return new EventLoopWorker(pool.get());
}
public int size() {
return pool.get().allWorkers.size();
}
static final class EventLoopWorker extends Scheduler.Worker {
private final CompositeDisposable tasks;
private final CachedWorkerPool pool;
private final ThreadWorker threadWorker;
final AtomicBoolean once = new AtomicBoolean();
EventLoopWorker(CachedWorkerPool pool) {
this.pool = pool;
this.tasks = new CompositeDisposable();
this.threadWorker = pool.get();
}
@Override
public void dispose() {
if (once.compareAndSet(false, true)) {
tasks.dispose();
// releasing the pool should be the last action
pool.release(threadWorker);
}
}
@Override
public boolean isDisposed() {
return once.get();
}
@NonNull
@Override
public Disposable schedule(@NonNull Runnable action, long delayTime, @NonNull TimeUnit unit) {
if (tasks.isDisposed()) {
// don't schedule, we are unsubscribed
return EmptyDisposable.INSTANCE;
}
return threadWorker.scheduleActual(action, delayTime, unit, tasks);
}
}
static final class ThreadWorker extends NewThreadWorker {
private long expirationTime;
ThreadWorker(ThreadFactory threadFactory) {
super(threadFactory);
this.expirationTime = 0L;
}
public long getExpirationTime() {
return expirationTime;
}
public void setExpirationTime(long expirationTime) {
this.expirationTime = expirationTime;
}
}
}