org.opensearch.nio.TaskScheduler Maven / Gradle / Ivy
/*
* SPDX-License-Identifier: Apache-2.0
*
* The OpenSearch Contributors require contributions made to
* this file be licensed under the Apache-2.0 license or a
* compatible open source license.
*/
/*
* 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.
*/
/*
* Modifications Copyright OpenSearch Contributors. See
* GitHub history for details.
*/
package org.opensearch.nio;
import java.util.Comparator;
import java.util.PriorityQueue;
/**
* A basic priority queue backed timer service. The service is thread local and should only be used by a
* single nio selector event loop thread.
*/
public class TaskScheduler {
private final PriorityQueue tasks = new PriorityQueue<>(Comparator.comparingLong(DelayedTask::getDeadline));
/**
* Schedule a task at the defined relative nanotime. When {@link #pollTask(long)} is called with a
* relative nanotime after the scheduled time, the task will be returned. This method returns a
* {@link Runnable} that can be run to cancel the scheduled task.
*
* @param task to schedule
* @param relativeNanos defining when to execute the task
* @return runnable that will cancel the task
*/
public Runnable scheduleAtRelativeTime(Runnable task, long relativeNanos) {
DelayedTask delayedTask = new DelayedTask(relativeNanos, task);
tasks.offer(delayedTask);
return delayedTask;
}
public Runnable pollTask(long relativeNanos) {
DelayedTask task;
while ((task = tasks.peek()) != null) {
if (relativeNanos - task.deadline >= 0) {
tasks.remove();
if (task.cancelled == false) {
return task.runnable;
}
} else {
return null;
}
}
return null;
}
long nanosUntilNextTask(long relativeNanos) {
DelayedTask nextTask = tasks.peek();
if (nextTask == null) {
return Long.MAX_VALUE;
} else {
return Math.max(nextTask.deadline - relativeNanos, 0);
}
}
private static class DelayedTask implements Runnable {
private final long deadline;
private final Runnable runnable;
private boolean cancelled = false;
private DelayedTask(long deadline, Runnable runnable) {
this.deadline = deadline;
this.runnable = runnable;
}
private long getDeadline() {
return deadline;
}
@Override
public void run() {
cancelled = true;
}
}
}