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 }