test/jdk/java/lang/management/ThreadMXBean/VirtualThreads.java

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/**
 * @test id=default
 * @bug 8284161 8290562 8303242
 * @summary Test java.lang.management.ThreadMXBean with virtual threads
 * @modules java.base/java.lang:+open java.management
 * @library /test/lib
 * @run junit/othervm/native --enable-native-access=ALL-UNNAMED VirtualThreads
 */

/**
 * @test id=no-vmcontinuations
 * @requires vm.continuations
 * @modules java.base/java.lang:+open java.management
 * @library /test/lib
 * @run junit/othervm -XX:+UnlockExperimentalVMOptions -XX:-VMContinuations VirtualThreads
 */

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;
import java.nio.channels.Selector;
import java.util.Arrays;
import java.util.Set;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.LockSupport;
import java.util.stream.Collectors;

import jdk.test.lib.thread.VThreadPinner;
import jdk.test.lib.thread.VThreadRunner;
import jdk.test.lib.thread.VThreadScheduler;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;
import static org.junit.jupiter.api.Assertions.*;
import static org.junit.jupiter.api.Assumptions.*;

public class VirtualThreads {

    /**
     * Test that ThreadMXBean.dumpAllThreads does not include virtual threads.
     */
    @ParameterizedTest
    @ValueSource(ints = {0, Integer.MAX_VALUE})
    void testDumpAllThreads(int maxDepth) {
        Thread vthread = Thread.startVirtualThread(LockSupport::park);
        try {
            ThreadMXBean bean = ManagementFactory.getThreadMXBean();
            ThreadInfo[] infos = bean.dumpAllThreads(false, false, maxDepth);
            Set<Long> tids = Arrays.stream(infos)
                    .map(ThreadInfo::getThreadId)
                    .collect(Collectors.toSet());

            // if current thread is a platform thread then it should be included
            boolean expected = !Thread.currentThread().isVirtual();
            assertEquals(expected, tids.contains(Thread.currentThread().threadId()));

            // virtual thread should not be included
            assertFalse(tids.contains(vthread.threadId()));
        } finally {
            LockSupport.unpark(vthread);
        }
    }

    /**
     * Test that ThreadMXBean::getAllThreadsIds does not include virtual threads.
     */
    @Test
    void testGetAllThreadIds() {
        Thread vthread = Thread.startVirtualThread(LockSupport::park);
        try {
            long[] tids = ManagementFactory.getThreadMXBean().getAllThreadIds();

            // if current thread is a platform thread then it should be included
            boolean expected = !Thread.currentThread().isVirtual();
            long currentTid = Thread.currentThread().threadId();
            assertEquals(expected, Arrays.stream(tids).anyMatch(tid -> tid == currentTid));

            // virtual thread should not be included
            long vtid = vthread.threadId();
            assertFalse(Arrays.stream(tids).anyMatch(tid -> tid == vtid));
        } finally {
            LockSupport.unpark(vthread);
        }
    }

    /**
     * Test that ThreadMXBean.getThreadInfo(long, maxDepth) returns null for a virtual
     * thread.
     */
    @ParameterizedTest
    @ValueSource(ints = {0, Integer.MAX_VALUE})
    void testGetThreadInfo1(int maxDepth) {
        Thread vthread = Thread.startVirtualThread(LockSupport::park);
        try {
            long tid = vthread.threadId();
            ThreadInfo info = ManagementFactory.getThreadMXBean().getThreadInfo(tid, maxDepth);
            assertNull(info);
        } finally {
            LockSupport.unpark(vthread);
        }
    }

    /**
     * Test that ThreadMXBean.getThreadInfo(long, maxDepth) returns null when invoked
     * by a virtual thread with its own thread id.
     */
    @ParameterizedTest
    @ValueSource(ints = {0, Integer.MAX_VALUE})
    void testGetThreadInfo2(int maxDepth) throws Exception {
        VThreadRunner.run(() -> {
            long tid = Thread.currentThread().threadId();
            ThreadInfo info = ManagementFactory.getThreadMXBean().getThreadInfo(tid, maxDepth);
            assertNull(info);
        });
    }

    /**
     * Test that ThreadMXBean.getThreadInfo(long[], maxDepth) returns a null ThreadInfo
     * for elements that correspond to a virtual thread.
     */
    @ParameterizedTest
    @ValueSource(ints = {0, Integer.MAX_VALUE})
    void testGetThreadInfo3(int maxDepth) {
        Thread vthread = Thread.startVirtualThread(LockSupport::park);
        try {
            long tid0 = Thread.currentThread().threadId();
            long tid1 = vthread.threadId();
            long[] tids = new long[] { tid0, tid1 };
            ThreadInfo[] infos = ManagementFactory.getThreadMXBean().getThreadInfo(tids, maxDepth);
            if (Thread.currentThread().isVirtual()) {
                assertNull(infos[0]);
            } else {
                assertEquals(tid0, infos[0].getThreadId());
            }
            assertNull(infos[1]);
        } finally {
            LockSupport.unpark(vthread);
        }
    }

    /**
     * Test that ThreadMXBean.getThreadInfo(long[], boolean, boolean, maxDepth) returns
     * a null ThreadInfo for elements that correspond to a virtual thread.
     */
    @ParameterizedTest
    @ValueSource(ints = {0, Integer.MAX_VALUE})
    void testGetThreadInfo4(int maxDepth) {
        Thread vthread = Thread.startVirtualThread(LockSupport::park);
        try {
            long tid0 = Thread.currentThread().threadId();
            long tid1 = vthread.threadId();
            long[] tids = new long[] { tid0, tid1 };
            ThreadMXBean bean = ManagementFactory.getThreadMXBean();
            ThreadInfo[] infos = bean.getThreadInfo(tids, false, false, maxDepth);
            if (Thread.currentThread().isVirtual()) {
                assertNull(infos[0]);
            } else {
                assertEquals(tid0, infos[0].getThreadId());
            }
            assertNull(infos[1]);
        } finally {
            LockSupport.unpark(vthread);
        }
    }

    /**
     * Test ThreadMXBean.getThreadInfo(long) with the thread id of a carrier thread.
     * The stack frames of the virtual thread should not be returned.
     */
    @Test
    void testGetThreadInfoCarrierThread() throws Exception {
        assumeTrue(VThreadScheduler.supportsCustomScheduler(), "No support for custom schedulers");
        try (ExecutorService pool = Executors.newFixedThreadPool(1)) {
            var carrierRef = new AtomicReference<Thread>();
            Executor scheduler = (task) -> {
                pool.execute(() -> {
                    carrierRef.set(Thread.currentThread());
                    task.run();
                });
            };
            ThreadFactory factory = VThreadScheduler.virtualThreadFactory(scheduler);

            // start virtual thread so carrier Thread can be captured
            Thread thread = factory.newThread(() -> { });
            thread.start();
            thread.join();
            Thread carrier = carrierRef.get();
            assertTrue(carrier != null && !carrier.isVirtual());

            try (Selector sel = Selector.open()) {
                String selClassName = sel.getClass().getName();

                // start virtual thread that blocks while pinned
                Thread vthread = factory.newThread(() -> {
                    try {
                        VThreadPinner.runPinned(sel::select);
                    } catch (Exception e) { }
                });
                vthread.start();

                // wait for virtual thread to block in select
                while (!contains(vthread.getStackTrace(), selClassName)) {
                    Thread.sleep(20);
                }

                // invoke getThreadInfo get and check the stack trace
                long tid = carrier.getId();
                ThreadInfo info = ManagementFactory.getThreadMXBean().getThreadInfo(tid, 100);

                // should only see carrier frames
                StackTraceElement[] stack = info.getStackTrace();
                assertTrue(contains(stack, "java.util.concurrent.ThreadPoolExecutor"));
                assertFalse(contains(stack, selClassName));

                // carrier should not be holding any monitors
                assertEquals(0, info.getLockedMonitors().length);
            }
        }
    }

    /**
     * Test that ThreadMXBean.getThreadCpuTime(long) returns -1 for a virtual thread.
     */
    @Test
    void testGetThreadCpuTime1() {
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();
        assumeTrue(bean.isThreadCpuTimeSupported(), "Thread CPU time measurement not supported");

        Thread vthread = Thread.startVirtualThread(LockSupport::park);
        try {
            long tid = vthread.threadId();
            long cpuTime = bean.getThreadCpuTime(tid);
            assertEquals(-1L, cpuTime);
        } finally {
            LockSupport.unpark(vthread);
        }
    }

    /**
     * Test that ThreadMXBean.getThreadCpuTime(long) returns -1 when invoked by a
     * virtual thread with its own thread id.
     */
    @Test
    void testGetThreadCpuTime2() throws Exception {
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();
        assumeTrue(bean.isThreadCpuTimeSupported(), "Thread CPU time measurement not supported");

        VThreadRunner.run(() -> {
            long tid = Thread.currentThread().threadId();
            long cpuTime = bean.getThreadCpuTime(tid);
            assertEquals(-1L, cpuTime);
        });
    }

    /**
     * Test that ThreadMXBean.getThreadUserTime(long) returns -1 for a virtual thread.
     */
    @Test
    void testGetThreadUserTime1() {
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();
        assumeTrue(bean.isThreadCpuTimeSupported(), "Thread CPU time measurement not supported");

        Thread vthread = Thread.startVirtualThread(LockSupport::park);
        try {
            long tid = vthread.threadId();
            long userTime = ManagementFactory.getThreadMXBean().getThreadUserTime(tid);
            assertEquals(-1L, userTime);
        } finally {
            LockSupport.unpark(vthread);
        }
    }

    /**
     * Test that ThreadMXBean.getThreadUserTime(long) returns -1 when invoked by a
     * virtual thread with its own thread id.
     */
    @Test
    void testGetThreadUserTime2() throws Exception {
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();
        assumeTrue(bean.isThreadCpuTimeSupported(), "Thread CPU time measurement not supported");

        VThreadRunner.run(() -> {
            long tid = Thread.currentThread().threadId();
            long userTime = ManagementFactory.getThreadMXBean().getThreadUserTime(tid);
            assertEquals(-1L, userTime);
        });
    }

    /**
     * Test that ThreadMXBean::isCurrentThreadCpuTimeSupported returns true when
     * CPU time measurement for the current thread is supported.
     */
    @Test
    void testIsCurrentThreadCpuTimeSupported() throws Exception {
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();
        assumeTrue(bean.isCurrentThreadCpuTimeSupported(),
                "Thread CPU time measurement for the current thread not supported");

        VThreadRunner.run(() -> {
            assertTrue(bean.isCurrentThreadCpuTimeSupported());
        });
    }

    /**
     * Test that ThreadMXBean::getCurrentThreadCpuTime returns -1 when invoked
     * from a virtual thread.
     */
    @Test
    void testGetCurrentThreadCpuTime() throws Exception {
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();
        assumeTrue(bean.isCurrentThreadCpuTimeSupported(),
                "Thread CPU time measurement for the current thread not supported");

        VThreadRunner.run(() -> {
            assertEquals(-1L, bean.getCurrentThreadCpuTime());
        });
    }

    /**
     * Test that ThreadMXBean::getCurrentThreadUserTime returns -1 when invoked
     * from a virtual thread.
     */
    @Test
    void testGetCurrentThreadUserTime() throws Exception {
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();
        assumeTrue(bean.isCurrentThreadCpuTimeSupported(),
                "Thread CPU time measurement for the current thread not supported");

        VThreadRunner.run(() -> {
            assertEquals(-1L, bean.getCurrentThreadUserTime());
        });
    }

    private static boolean contains(StackTraceElement[] stack, String className) {
        return Arrays.stream(stack)
                .map(StackTraceElement::getClassName)
                .anyMatch(className::equals);
    }
}