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Parallel programming on the go
/*
* 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.gh.bmd.jrt.runner;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import javax.annotation.Nonnull;
/**
* Utility class for creating and sharing runner instances.
*
* Created by davide-maestroni on 9/9/14.
*/
public class Runners {
private static final Object sMutex = new Object();
private static final QueuedRunner sQueuedRunner = new QueuedRunner();
private static final SequentialRunner sSequentialRunner = new SequentialRunner();
private static Runner sSharedRunner;
/**
* Avoid direct instantiation.
*/
protected Runners() {
}
/**
* Returns a runner employing a dynamic pool of threads.
* The number of threads may increase when needed from the core to the maximum pool size. The
* number of threads exceeding the core size are kept alive when idle for the specified time.
* If they stay idle for more time they will be destroyed.
*
* @param corePoolSize the number of threads to keep in the pool, even if they are idle.
* @param maximumPoolSize the maximum number of threads to allow in the pool.
* @param keepAliveTime when the number of threads is greater than the core one, this is the
* maximum time that excess idle threads will wait for new tasks before
* terminating.
* @param keepAliveUnit the time unit for the keep alive time.
* @return the runner instance.
*/
@Nonnull
public static Runner dynamicPoolRunner(final int corePoolSize, final int maximumPoolSize,
final long keepAliveTime, @Nonnull final TimeUnit keepAliveUnit) {
return scheduledRunner(
new DynamicScheduledThreadExecutor(corePoolSize, maximumPoolSize, keepAliveTime,
keepAliveUnit));
}
/**
* Returns a runner employing the specified number of threads.
*
* @param poolSize the thread pool size.
* @return the runner instance.
*/
@Nonnull
public static Runner poolRunner(final int poolSize) {
return scheduledRunner(Executors.newScheduledThreadPool(poolSize));
}
/**
* Returns a runner employing an optimum number of threads.
*
* @return the runner instance.
*/
@Nonnull
public static Runner poolRunner() {
return poolRunner(Runtime.getRuntime().availableProcessors() << 1);
}
/**
* Returns a runner providing ordering of executions based on priority.
*
* @param wrapped the wrapped runner instance.
* @return the runner instance.
*/
@Nonnull
public static PriorityRunner priorityRunner(@Nonnull final Runner wrapped) {
return new PriorityRunner(wrapped);
}
/**
* Returns the shared instance of a queued synchronous runner.
*
* @return the runner instance.
*/
@Nonnull
public static Runner queuedRunner() {
return sQueuedRunner;
}
/**
* Returns a runner employing the specified executor service.
*
* @param service the executor service.
* @return the runner instance.
*/
@Nonnull
public static Runner scheduledRunner(@Nonnull final ScheduledExecutorService service) {
return new ScheduledRunner(service);
}
/**
* Returns the shared instance of a sequential synchronous runner.
*
* @return the runner instance.
*/
@Nonnull
public static Runner sequentialRunner() {
return sSequentialRunner;
}
/**
* Returns the shared instance of a thread pool asynchronous runner.
*
* @return the runner instance.
*/
@Nonnull
public static Runner sharedRunner() {
synchronized (sMutex) {
if (sSharedRunner == null) {
final int processors = Runtime.getRuntime().availableProcessors();
sSharedRunner = dynamicPoolRunner((processors <= 2) ? processors : processors - 1,
(processors << 3) - 1, 3L, TimeUnit.SECONDS);
}
return sSharedRunner;
}
}
}