rx.internal.schedulers.GenericScheduledExecutorService Maven / Gradle / Ivy
/**
* Copyright 2014 Netflix, Inc.
*
* 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 rx.internal.schedulers;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicReference;
import rx.Scheduler;
/**
* A default {@link ScheduledExecutorService} that can be used for scheduling actions when a {@link Scheduler} implementation doesn't have that ability.
*
* For example if a {@link Scheduler} is given an {@link Executor} or {{@link ExecutorService} instead of {@link ScheduledExecutorService}.
*
* NOTE: No actual work should be done on tasks submitted to this executor. Submit a task with the appropriate delay which then in turn invokes
* the work asynchronously on the appropriate {@link Scheduler} implementation. This means for example that you would not use this approach
* along with {@link TrampolineScheduler} or {@link ImmediateScheduler}.
*/
public final class GenericScheduledExecutorService implements SchedulerLifecycle {
private static final ScheduledExecutorService[] NONE = new ScheduledExecutorService[0];
private static final ScheduledExecutorService SHUTDOWN;
static {
SHUTDOWN = Executors.newScheduledThreadPool(0);
SHUTDOWN.shutdown();
}
/* Schedulers needs access to this in order to work with the lifecycle. */
public final static GenericScheduledExecutorService INSTANCE = new GenericScheduledExecutorService();
private final AtomicReference executor;
/** We don't use atomics with this because thread-assignment is random anyway. */
private static int roundRobin;
private GenericScheduledExecutorService() {
executor = new AtomicReference(NONE);
start();
}
@Override
public void start() {
int count = Runtime.getRuntime().availableProcessors();
if (count > 4) {
count = count / 2;
}
// we don't need more than 8 to handle just scheduling and doing no work
if (count > 8) {
count = 8;
}
// A multi-threaded executor can reorder tasks, having a set of them
// and handing one of those out on getInstance() ensures a proper order
ScheduledExecutorService[] execs = new ScheduledExecutorService[count];
for (int i = 0; i < count; i++) {
execs[i] = GenericScheduledExecutorServiceFactory.create();
}
if (executor.compareAndSet(NONE, execs)) {
for (ScheduledExecutorService exec : execs) {
if (!NewThreadWorker.tryEnableCancelPolicy(exec)) {
if (exec instanceof ScheduledThreadPoolExecutor) {
NewThreadWorker.registerExecutor((ScheduledThreadPoolExecutor)exec);
}
}
}
} else {
for (ScheduledExecutorService exec : execs) {
exec.shutdownNow();
}
}
}
@Override
public void shutdown() {
for (;;) {
ScheduledExecutorService[] execs = executor.get();
if (execs == NONE) {
return;
}
if (executor.compareAndSet(execs, NONE)) {
for (ScheduledExecutorService exec : execs) {
NewThreadWorker.deregisterExecutor(exec);
exec.shutdownNow();
}
return;
}
}
}
/**
* Returns one of the single-threaded ScheduledExecutorService helper executors.
*
* @return {@link ScheduledExecutorService} for generic use.
*/
public static ScheduledExecutorService getInstance() {
ScheduledExecutorService[] execs = INSTANCE.executor.get();
if (execs == NONE) {
return SHUTDOWN;
}
int r = roundRobin + 1;
if (r >= execs.length) {
r = 0;
}
roundRobin = r;
return execs[r];
}
}