org.onlab.util.OrderedExecutor Maven / Gradle / Ivy
/*
* Copyright 2017-present Open Networking Foundation
*
* 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 org.onlab.util;
import java.util.LinkedList;
import java.util.concurrent.Executor;
/**
* Executor that executes tasks in order on a shared thread pool.
*
* The ordered executor behaves semantically like a single-threaded executor, but multiplexes tasks on a shared thread
* pool, ensuring blocked threads in the shared thread pool don't block individual ordered executors.
*/
public class OrderedExecutor implements Executor {
private final Executor parent;
private final LinkedList tasks = new LinkedList<>();
private boolean running;
public OrderedExecutor(Executor parent) {
this.parent = parent;
}
private void run() {
for (;;) {
final Runnable task;
synchronized (tasks) {
task = tasks.poll();
if (task == null) {
running = false;
return;
}
}
task.run();
}
}
@Override
public void execute(Runnable command) {
synchronized (tasks) {
tasks.add(command);
if (!running) {
running = true;
parent.execute(this::run);
}
}
}
}