adoroszlai commented on a change in pull request #3180:
URL: https://github.com/apache/ozone/pull/3180#discussion_r830653688
##########
File path:
hadoop-ozone/common/src/main/java/org/apache/hadoop/ozone/om/lock/OzoneManagerLock.java
##########
@@ -172,7 +176,16 @@ private boolean lock(Resource resource, String
resourceName,
LOG.error(errorMessage);
throw new RuntimeException(errorMessage);
} else {
+ long startWaitingTimeNanos = Time.monotonicNowNanos();
+ /**
+ * holdCount helps in metric updation only once in case of reentrant
+ * locks.
+ */
+ int holdCount = manager.getActiveLockCount(resourceName);
lockFn.accept(resourceName);
+ if (holdCount == 0) {
+ updateReadLockMetrics(resource, lockType, startWaitingTimeNanos);
+ }
Review comment:
Here's a test case to reproduce the multiple readers problem I mentioned:
```java
@Test
public void testReadLockConcurrentStats() throws InterruptedException {
// GIVEN
final int threadCount = 5;
OzoneManagerLock.Resource resource =
OzoneManagerLock.Resource.VOLUME_LOCK;
String[] resourceName = generateResourceName(resource);
OzoneManagerLock lock = new OzoneManagerLock(new OzoneConfiguration());
Thread[] threads = new Thread[threadCount];
for (int i = 0; i < threads.length; i++) {
threads[i] = new Thread(() -> {
lock.acquireReadLock(resource, resourceName);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
lock.releaseReadLock(resource, resourceName);
});
threads[i].start();
}
for (Thread t : threads) {
t.join();
}
// WHEN
String heldStat = lock.getReadLockHeldTimeMsStat();
// THEN
Assert.assertTrue("Expected " + threadCount + " samples in " + heldStat,
heldStat.contains("Samples = " + threadCount));
}
```
Result:
```
[ERROR] Failures:
[ERROR] TestOzoneManagerLock.testReadLockConcurrentStats:389 Expected 5
samples in Samples = 1 Min = 1.26694054E8 Mean = 1.26694054E8 Std Dev = 0.0
Max = 1.26694054E8
```
Only one of the 5 threads that acquire the read lock are reflected by the
metrics stat.
Similar test case can be constructed for 1 writer + N readers.
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