[HBASE-15319] clearJmxCache does not take effect actually

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.2.0, 1.1.0.1, 1.3.0, 2.0.0
• Fix Version/s: 1.3.0, 1.2.1, 2.0.0
• Component/s: metrics
• Labels: easyfix
• Hadoop Flags: Reviewed
• Assignee: Elliott Neil Clark
• Reporter: Hao Lin
• Created: 24/Feb/16 03:34
• Updated: 25/Feb/16 06:20
• Resolved: 25/Feb/16 00:34

Description

When trying to backport HBASE-14166 to 0.98.6, I find JmxCacheBuster::clearJmxCache() does no take effect actually. The related code are listed below:

org.apache.hadoop.metrics2.impl.JmxCacheBuster.java

// fut is initialized to null
private static AtomicReference<ScheduledFuture> fut = new AtomicReference<>(null);

public static void clearJmxCache() {
    // clearJmxCache return directly when fut is null, which is always true.
    // the actual intent is 'if (future != null && !future.isDone ...)' ?
    ScheduledFuture future = fut.get();
    if ((future == null || (!future.isDone() && future.getDelay(TimeUnit.MILLISECONDS) > 100))) {
      return;
    }
    ......
}