1 /*
2 * Copyright (c) 2022, 2023, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24 package jdk.test.lib.thread;
25
26 import java.lang.reflect.Field;
27 import java.time.Duration;
28 import java.util.concurrent.ForkJoinPool;
29 import java.util.concurrent.atomic.AtomicReference;
30
31 /**
32 * Helper class to support tests running tasks in a virtual thread.
33 */
34 public class VThreadRunner {
35 private VThreadRunner() { }
36
37 /**
38 * Characteristic value signifying that initial values for inheritable
39 * thread locals are not inherited from the constructing thread.
40 */
41 public static final int NO_INHERIT_THREAD_LOCALS = 1 << 2;
42
43 /**
44 * Represents a task that does not return a result but may throw
45 * an exception.
46 */
47 @FunctionalInterface
48 public interface ThrowingRunnable {
49 /**
50 * Runs this operation.
51 */
52 void run() throws Exception;
53 }
54
55 /**
56 * Run a task in a virtual thread and wait for it to terminate.
57 * If the task completes with an exception then it is thrown by this method.
58 * If the task throws an Error then it is wrapped in an RuntimeException.
59 *
60 * @param name thread name, can be null
61 * @param characteristics thread characteristics
62 * @param task the task to run
63 * @throws Exception the exception thrown by the task
64 */
65 public static void run(String name,
66 int characteristics,
67 ThrowingRunnable task) throws Exception {
68 AtomicReference<Exception> exc = new AtomicReference<>();
69 Runnable target = () -> {
70 try {
71 task.run();
72 } catch (Error e) {
73 exc.set(new RuntimeException(e));
74 } catch (Exception e) {
75 exc.set(e);
76 }
77 };
78
79 Thread.Builder builder = Thread.ofVirtual();
80 if (name != null)
81 builder.name(name);
82 if ((characteristics & NO_INHERIT_THREAD_LOCALS) != 0)
83 builder.inheritInheritableThreadLocals(false);
84 Thread thread = builder.start(target);
85
86 // wait for thread to terminate
87 while (thread.join(Duration.ofSeconds(10)) == false) {
88 System.out.println("-- " + thread + " --");
89 for (StackTraceElement e : thread.getStackTrace()) {
90 System.out.println(" " + e);
91 }
92 }
93
94 Exception e = exc.get();
95 if (e != null) {
96 throw e;
97 }
98 }
99
100 /**
101 * Run a task in a virtual thread and wait for it to terminate.
102 * If the task completes with an exception then it is thrown by this method.
103 * If the task throws an Error then it is wrapped in an RuntimeException.
104 *
105 * @param name thread name, can be null
106 * @param task the task to run
107 * @throws Exception the exception thrown by the task
108 */
109 public static void run(String name, ThrowingRunnable task) throws Exception {
110 run(name, 0, task);
111 }
112
113 /**
114 * Run a task in a virtual thread and wait for it to terminate.
115 * If the task completes with an exception then it is thrown by this method.
116 * If the task throws an Error then it is wrapped in an RuntimeException.
117 *
118 * @param characteristics thread characteristics
119 * @param task the task to run
120 * @throws Exception the exception thrown by the task
121 */
122 public static void run(int characteristics, ThrowingRunnable task) throws Exception {
123 run(null, characteristics, task);
124 }
125
126 /**
127 * Run a task in a virtual thread and wait for it to terminate.
128 * If the task completes with an exception then it is thrown by this method.
129 * If the task throws an Error then it is wrapped in an RuntimeException.
130 *
131 * @param task the task to run
132 * @throws Exception the exception thrown by the task
133 */
134 public static void run(ThrowingRunnable task) throws Exception {
135 run(null, 0, task);
136 }
137
138 /**
139 * Returns the virtual thread scheduler.
140 */
141 private static ForkJoinPool defaultScheduler() {
142 try {
143 var clazz = Class.forName("java.lang.VirtualThread");
144 var field = clazz.getDeclaredField("DEFAULT_SCHEDULER");
145 field.setAccessible(true);
146 return (ForkJoinPool) field.get(null);
147 } catch (Exception e) {
148 throw new RuntimeException(e);
149 }
150 }
151
152 /**
153 * Sets the virtual thread scheduler's target parallelism.
154 * @return the previous parallelism level
155 */
156 public static int setParallelism(int size) {
157 return defaultScheduler().setParallelism(size);
158 }
159
160 /**
161 * Ensures that the virtual thread scheduler's target parallelism is at least
162 * the given size. If the target parallelism is less than the given size then
163 * it is changed to the given size.
164 * @return the previous parallelism level
165 */
166 public static int ensureParallelism(int size) {
167 ForkJoinPool pool = defaultScheduler();
168 int parallelism = pool.getParallelism();
169 if (size > parallelism) {
170 pool.setParallelism(size);
171 }
172 return parallelism;
173 }
174 }