| /* |
| * 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. |
| * <p> |
| * 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<Runnable> 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); |
| } |
| } |
| } |
| } |