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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.threadpool;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.unit.TimeValue;
import org.elasticsearch.common.util.concurrent.AbstractRunnable;
import org.elasticsearch.common.util.concurrent.EsAbortPolicy;
import org.elasticsearch.common.util.concurrent.EsExecutors;
import org.elasticsearch.common.util.concurrent.EsRejectedExecutionException;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;
/**
* Scheduler that allows to schedule one-shot and periodic commands.
*/
public interface Scheduler {
static ScheduledThreadPoolExecutor initScheduler(Settings settings) {
ScheduledThreadPoolExecutor scheduler = new ScheduledThreadPoolExecutor(1,
EsExecutors.daemonThreadFactory(settings, "scheduler"), new EsAbortPolicy());
scheduler.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
scheduler.setContinueExistingPeriodicTasksAfterShutdownPolicy(false);
scheduler.setRemoveOnCancelPolicy(true);
return scheduler;
}
static boolean terminate(ScheduledThreadPoolExecutor scheduledThreadPoolExecutor, long timeout, TimeUnit timeUnit) {
scheduledThreadPoolExecutor.shutdown();
if (awaitTermination(scheduledThreadPoolExecutor, timeout, timeUnit)) {
return true;
}
// last resort
scheduledThreadPoolExecutor.shutdownNow();
return awaitTermination(scheduledThreadPoolExecutor, timeout, timeUnit);
}
static boolean awaitTermination(final ScheduledThreadPoolExecutor scheduledThreadPoolExecutor,
final long timeout, final TimeUnit timeUnit) {
try {
if (scheduledThreadPoolExecutor.awaitTermination(timeout, timeUnit)) {
return true;
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
return false;
}
/**
* Does nothing by default but can be used by subclasses to save the current thread context and wraps the command in a Runnable
* that restores that context before running the command.
*/
default Runnable preserveContext(Runnable command) {
return command;
}
/**
* Schedules a one-shot command to be run after a given delay. The command is not run in the context of the calling thread.
* To preserve the context of the calling thread you may call {@link #preserveContext(Runnable)} on the runnable before passing
* it to this method.
* The command runs on scheduler thread. Do not run blocking calls on the scheduler thread. Subclasses may allow
* to execute on a different executor, in which case blocking calls are allowed.
*
* @param delay delay before the task executes
* @param executor the name of the executor that has to execute this task. Ignored in the default implementation but can be used
* by subclasses that support multiple executors.
* @param command the command to run
* @return a ScheduledFuture who's get will return when the task has been added to its target thread pool and throws an exception if
* the task is canceled before it was added to its target thread pool. Once the task has been added to its target thread pool
* the ScheduledFuture cannot interact with it.
* @throws EsRejectedExecutionException if the task cannot be scheduled for execution
*/
ScheduledFuture schedule(TimeValue delay, String executor, Runnable command);
/**
* Schedules a periodic action that runs on scheduler thread. Do not run blocking calls on the scheduler thread. Subclasses may allow
* to execute on a different executor, in which case blocking calls are allowed.
*
* @param command the action to take
* @param interval the delay interval
* @param executor the name of the executor that has to execute this task. Ignored in the default implementation but can be used
* by subclasses that support multiple executors.
* @return a {@link Cancellable} that can be used to cancel the subsequent runs of the command. If the command is running, it will
* not be interrupted.
*/
default Cancellable scheduleWithFixedDelay(Runnable command, TimeValue interval, String executor) {
return new ReschedulingRunnable(command, interval, executor, this, (e) -> {}, (e) -> {});
}
/**
* This interface represents an object whose execution may be cancelled during runtime.
*/
interface Cancellable {
/**
* Cancel the execution of this object. This method is idempotent.
*/
void cancel();
/**
* Check if the execution has been cancelled
* @return true if cancelled
*/
boolean isCancelled();
}
/**
* This class encapsulates the scheduling of a {@link Runnable} that needs to be repeated on a interval. For example, checking a value
* for cleanup every second could be done by passing in a Runnable that can perform the check and the specified interval between
* executions of this runnable. NOTE: the runnable is only rescheduled to run again after completion of the runnable.
*
* For this class, completion means that the call to {@link Runnable#run()} returned or an exception was thrown and caught. In
* case of an exception, this class will log the exception and reschedule the runnable for its next execution. This differs from the
* {@link ScheduledThreadPoolExecutor#scheduleWithFixedDelay(Runnable, long, long, TimeUnit)} semantics as an exception there would
* terminate the rescheduling of the runnable.
*/
final class ReschedulingRunnable extends AbstractRunnable implements Cancellable {
private final Runnable runnable;
private final TimeValue interval;
private final String executor;
private final Scheduler scheduler;
private final Consumer rejectionConsumer;
private final Consumer failureConsumer;
private volatile boolean run = true;
/**
* Creates a new rescheduling runnable and schedules the first execution to occur after the interval specified
*
* @param runnable the {@link Runnable} that should be executed periodically
* @param interval the time interval between executions
* @param executor the executor where this runnable should be scheduled to run
* @param scheduler the {@link Scheduler} instance to use for scheduling
*/
ReschedulingRunnable(Runnable runnable, TimeValue interval, String executor, Scheduler scheduler,
Consumer rejectionConsumer, Consumer failureConsumer) {
this.runnable = runnable;
this.interval = interval;
this.executor = executor;
this.scheduler = scheduler;
this.rejectionConsumer = rejectionConsumer;
this.failureConsumer = failureConsumer;
scheduler.schedule(interval, executor, this);
}
@Override
public void cancel() {
run = false;
}
@Override
public boolean isCancelled() {
return run == false;
}
@Override
public void doRun() {
// always check run here since this may have been cancelled since the last execution and we do not want to run
if (run) {
runnable.run();
}
}
@Override
public void onFailure(Exception e) {
failureConsumer.accept(e);
}
@Override
public void onRejection(Exception e) {
run = false;
rejectionConsumer.accept(e);
}
@Override
public void onAfter() {
// if this has not been cancelled reschedule it to run again
if (run) {
try {
scheduler.schedule(interval, executor, this);
} catch (final EsRejectedExecutionException e) {
onRejection(e);
}
}
}
}
}
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