Jordan Halterman | 9bdc24f | 2017-04-19 23:45:12 -0700 | [diff] [blame] | 1 | /* |
Brian O'Connor | a09fe5b | 2017-08-03 21:12:30 -0700 | [diff] [blame] | 2 | * Copyright 2017-present Open Networking Foundation |
Jordan Halterman | 9bdc24f | 2017-04-19 23:45:12 -0700 | [diff] [blame] | 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | package org.onlab.util; |
| 17 | |
| 18 | import java.util.LinkedList; |
| 19 | import java.util.concurrent.Executor; |
| 20 | |
| 21 | /** |
Jordan Halterman | 046faeb | 2017-05-01 15:10:13 -0700 | [diff] [blame] | 22 | * Executor that executes tasks in order on a shared thread pool. |
Jordan Halterman | 9bdc24f | 2017-04-19 23:45:12 -0700 | [diff] [blame] | 23 | * <p> |
Jordan Halterman | 046faeb | 2017-05-01 15:10:13 -0700 | [diff] [blame] | 24 | * The ordered executor behaves semantically like a single-threaded executor, but multiplexes tasks on a shared thread |
| 25 | * pool, ensuring blocked threads in the shared thread pool don't block individual ordered executors. |
Jordan Halterman | 9bdc24f | 2017-04-19 23:45:12 -0700 | [diff] [blame] | 26 | */ |
Jordan Halterman | 046faeb | 2017-05-01 15:10:13 -0700 | [diff] [blame] | 27 | public class OrderedExecutor implements Executor { |
Jordan Halterman | 9bdc24f | 2017-04-19 23:45:12 -0700 | [diff] [blame] | 28 | private final Executor parent; |
| 29 | private final LinkedList<Runnable> tasks = new LinkedList<>(); |
| 30 | private boolean running; |
| 31 | |
Jordan Halterman | 046faeb | 2017-05-01 15:10:13 -0700 | [diff] [blame] | 32 | public OrderedExecutor(Executor parent) { |
Jordan Halterman | 9bdc24f | 2017-04-19 23:45:12 -0700 | [diff] [blame] | 33 | this.parent = parent; |
| 34 | } |
| 35 | |
| 36 | private void run() { |
| 37 | for (;;) { |
| 38 | final Runnable task; |
| 39 | synchronized (tasks) { |
| 40 | task = tasks.poll(); |
| 41 | if (task == null) { |
| 42 | running = false; |
| 43 | return; |
| 44 | } |
| 45 | } |
| 46 | task.run(); |
| 47 | } |
| 48 | } |
| 49 | |
| 50 | @Override |
| 51 | public void execute(Runnable command) { |
| 52 | synchronized (tasks) { |
| 53 | tasks.add(command); |
| 54 | if (!running) { |
| 55 | running = true; |
| 56 | parent.execute(this::run); |
| 57 | } |
| 58 | } |
| 59 | } |
| 60 | } |