1 /*
2 * Copyright 2017 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
17 package io.netty.util;
18
19 import io.netty.util.internal.ObjectUtil;
20 import io.netty.util.internal.SystemPropertyUtil;
21
22 import java.util.Locale;
23
24 /**
25 * A utility class for wrapping calls to {@link Runtime}.
26 */
27 public final class NettyRuntime {
28
29 /**
30 * Holder class for available processors to enable testing.
31 */
32 static class AvailableProcessorsHolder {
33
34 private int availableProcessors;
35
36 /**
37 * Set the number of available processors.
38 *
39 * @param availableProcessors the number of available processors
40 * @throws IllegalArgumentException if the specified number of available processors is non-positive
41 * @throws IllegalStateException if the number of available processors is already configured
42 */
43 synchronized void setAvailableProcessors(final int availableProcessors) {
44 ObjectUtil.checkPositive(availableProcessors, "availableProcessors");
45 if (this.availableProcessors != 0) {
46 final String message = String.format(
47 Locale.ROOT,
48 "availableProcessors is already set to [%d], rejecting [%d]",
49 this.availableProcessors,
50 availableProcessors);
51 throw new IllegalStateException(message);
52 }
53 this.availableProcessors = availableProcessors;
54 }
55
56 /**
57 * Get the configured number of available processors. The default is {@link Runtime#availableProcessors()}.
58 * This can be overridden by setting the system property "io.netty.availableProcessors" or by invoking
59 * {@link #setAvailableProcessors(int)} before any calls to this method.
60 *
61 * @return the configured number of available processors
62 */
63 @SuppressForbidden(reason = "to obtain default number of available processors")
64 synchronized int availableProcessors() {
65 if (this.availableProcessors == 0) {
66 final int availableProcessors =
67 SystemPropertyUtil.getInt(
68 "io.netty.availableProcessors",
69 Runtime.getRuntime().availableProcessors());
70 setAvailableProcessors(availableProcessors);
71 }
72 return this.availableProcessors;
73 }
74 }
75
76 private static final AvailableProcessorsHolder holder = new AvailableProcessorsHolder();
77
78 /**
79 * Set the number of available processors.
80 *
81 * @param availableProcessors the number of available processors
82 * @throws IllegalArgumentException if the specified number of available processors is non-positive
83 * @throws IllegalStateException if the number of available processors is already configured
84 */
85 @SuppressWarnings("unused,WeakerAccess") // this method is part of the public API
86 public static void setAvailableProcessors(final int availableProcessors) {
87 holder.setAvailableProcessors(availableProcessors);
88 }
89
90 /**
91 * Get the configured number of available processors. The default is {@link Runtime#availableProcessors()}. This
92 * can be overridden by setting the system property "io.netty.availableProcessors" or by invoking
93 * {@link #setAvailableProcessors(int)} before any calls to this method.
94 *
95 * @return the configured number of available processors
96 */
97 public static int availableProcessors() {
98 return holder.availableProcessors();
99 }
100
101 /**
102 * No public constructor to prevent instances from being created.
103 */
104 private NettyRuntime() {
105 }
106 }