jsedding commented on code in PR #3069:
URL: https://github.com/apache/jackrabbit-oak/pull/3069#discussion_r3794304044
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oak-auth-external/src/test/java/org/apache/jackrabbit/oak/spi/security/authentication/external/impl/principal/SyncConfigTrackerConcurrencyTest.java:
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@@ -123,51 +138,56 @@ public void concurrentGetServiceReferencesBlocksReaders()
throws Exception {
*/
@Test
public void concurrentIsEnabledDoesNotBlockReaders() throws Exception {
- boolean blockedOnTracked =
sampleForBlockingOnTrackedMonitor(tracker::isEnabled);
- assertFalse("expected isEnabled() to no longer contend on the
ServiceTracker$Tracked monitor "
- + "once service references are cached (OAK-12341)",
blockedOnTracked);
+ long blockedMs = sampleForBlockingOnTrackedMonitor(tracker::isEnabled);
+ LOG.info("Contended threads were blocked for {}ms", blockedMs);
+ assertEquals("expected isEnabled() to no longer contend on the
ServiceTracker$Tracked monitor "
+ + "once service references are cached (OAK-12341)", 0,
blockedMs);
}
/**
- * Runs {@code action} on {@link #THREAD_COUNT} threads in a tight loop for
- * {@link #SAMPLE_MILLIS} and polls {@link ThreadMXBean} throughout,
returning {@code true} as
- * soon as any thread is observed {@code BLOCKED} while waiting to lock a
- * {@code ServiceTracker$Tracked} instance held by another thread.
+ * Runs {@code action} directly on {@link #THREAD_COUNT} threads in a
tight loop, so all of
+ * them contend on the tracker concurrently from the start rather than
serializing through a
+ * single task submitter, and polls the {@link ThreadMXBean} of all worker
threads in a batch
+ * for {@link #SAMPLE_MILLIS}, returning the accumulated blocked time
observed on a
+ * {@code ServiceTracker$Tracked} monitor.
*/
- @SuppressWarnings("deprecation") // Thread.threadId() replacement requires
Java 19+; this module targets 17
- private boolean sampleForBlockingOnTrackedMonitor(Runnable action) throws
Exception {
+ private long sampleForBlockingOnTrackedMonitor(Runnable action) throws
Exception {
+ ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();
+ assumeTrue("JVM supporting thread contention monitoring required",
+ threadMXBean.isThreadContentionMonitoringSupported());
+ threadMXBean.setThreadContentionMonitoringEnabled(true);
+
ExecutorService pool = Executors.newFixedThreadPool(THREAD_COUNT);
- CountDownLatch started = new CountDownLatch(THREAD_COUNT);
+ CountDownLatch allThreadsStarted = new CountDownLatch(THREAD_COUNT);
AtomicBoolean stop = new AtomicBoolean(false);
- List<Long> threadIds = new CopyOnWriteArrayList<>();
+ long[] threadIds = new long[THREAD_COUNT];
Review Comment:
While it is safe to _write_ to the array from multiple threads, as long as
each thread only writes to a given array index (what you are doing here), there
is no guarantee that these updates are visible to other threads. I.e. the call
to `threadMXBean.getThreadInfo(threadIds)` _may_ not see the thread ID written
into the array (and would presumably see `null`).
See https://stackoverflow.com/a/8978397
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