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.netty5.util.concurrent;
17
18 import io.netty5.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 = (task, executor) -> {
29 throw new RejectedExecutionException();
30 };
31
32 private RejectedExecutionHandlers() { }
33
34 /**
35 * Returns a {@link RejectedExecutionHandler} that will always just throw a {@link RejectedExecutionException}.
36 */
37 public static RejectedExecutionHandler reject() {
38 return REJECT;
39 }
40
41 /**
42 * Tries to backoff when the task can not be added due restrictions for an configured amount of time. This
43 * is only done if the task was added from outside of the event loop which means
44 * {@link EventExecutor#inEventLoop()} returns {@code false}.
45 */
46 public static RejectedExecutionHandler backoff(final int retries, long backoffAmount, TimeUnit unit) {
47 ObjectUtil.checkPositive(retries, "retries");
48 final long backOffNanos = unit.toNanos(backoffAmount);
49 return (task, executor) -> {
50 if (!executor.inEventLoop()) {
51 for (int i = 0; i < retries; i++) {
52 // Try to wake up the executor so it will empty its task queue.
53 executor.wakeup(false);
54
55 LockSupport.parkNanos(backOffNanos);
56 if (executor.offerTask(task)) {
57 return;
58 }
59 }
60 }
61 // Either we tried to add the task from within the EventLoop or we was not able to add it even with
62 // backoff.
63 throw new RejectedExecutionException();
64 };
65 }
66 }