1 /*
2 * Copyright 2016 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://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, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.util.concurrent;
17
18 import io.netty.util.internal.ObjectUtil;
19
20 import java.util.concurrent.RejectedExecutionException;
21 import java.util.concurrent.TimeUnit;
22 import java.util.concurrent.locks.LockSupport;
23
24 /**
25 * Expose helper methods which create different {@link RejectedExecutionHandler}s.
26 */
27 public final class RejectedExecutionHandlers {
28 private static final RejectedExecutionHandler REJECT = new RejectedExecutionHandler() {
29 @Override
30 public void rejected(Runnable task, SingleThreadEventExecutor executor) {
31 throw new RejectedExecutionException();
32 }
33 };
34
35 private RejectedExecutionHandlers() { }
36
37 /**
38 * Returns a {@link RejectedExecutionHandler} that will always just throw a {@link RejectedExecutionException}.
39 */
40 public static RejectedExecutionHandler reject() {
41 return REJECT;
42 }
43
44 /**
45 * Tries to backoff when the task can not be added due restrictions for an configured amount of time. This
46 * is only done if the task was added from outside of the event loop which means
47 * {@link EventExecutor#inEventLoop()} returns {@code false}.
48 */
49 public static RejectedExecutionHandler backoff(final int retries, long backoffAmount, TimeUnit unit) {
50 ObjectUtil.checkPositive(retries, "retries");
51 final long backOffNanos = unit.toNanos(backoffAmount);
52 return new RejectedExecutionHandler() {
53 @Override
54 public void rejected(Runnable task, SingleThreadEventExecutor executor) {
55 if (!executor.inEventLoop()) {
56 for (int i = 0; i < retries; i++) {
57 // Try to wake up the executor so it will empty its task queue.
58 executor.wakeup(false);
59
60 LockSupport.parkNanos(backOffNanos);
61 if (executor.offerTask(task)) {
62 return;
63 }
64 }
65 }
66 // Either we tried to add the task from within the EventLoop or we was not able to add it even with
67 // backoff.
68 throw new RejectedExecutionException();
69 }
70 };
71 }
72 }