[YARN-11139] Minor performance improvements in DelegationTokenRenewerPoolTracker

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 3.3.1, 3.3.3
• Component/s: resourcemanager
• Labels: pull-request-available

Environment

Hadoop3.3.1 with Kerberos

• Assignee: Unassigned
• Reporter: YulongZ
• Created: 09/May/22 05:20
• Updated: 02/Jul/22 15:25

Description

The DelegationTokenRenewerPoolTracker thread wastes of CPU resources when no application running，the run method always executes a for loop, but actually does nothing. 

// code with no change
@Override
    public void run() {
      while (true) {
        for (Map.Entry<DelegationTokenRenewerEvent, Future<?>> entry : futures
            .entrySet()) {
          DelegationTokenRenewerEvent evt = entry.getKey();
          Future<?> future = entry.getValue();
          try {
            future.get(tokenRenewerThreadTimeout, TimeUnit.MILLISECONDS);
          } catch (TimeoutException e) {

            // Cancel thread and retry the same event in case of timeout
            if (future != null && !future.isDone() && !future.isCancelled()) {
              future.cancel(true);
              futures.remove(evt);
              if (evt.getAttempt() < tokenRenewerThreadRetryMaxAttempts) {
                renewalTimer.schedule(
                    getTimerTask((AbstractDelegationTokenRenewerAppEvent) evt),
                    tokenRenewerThreadRetryInterval);
              } else {
                LOG.info(
                    "Exhausted max retry attempts {} in token renewer "
                        + "thread for {}",
                    tokenRenewerThreadRetryMaxAttempts, evt.getApplicationId());
              }
            }
          } catch (Exception e) {
            LOG.info("Problem in submitting renew tasks in token renewer "
                + "thread.", e);
          }
        }
      }
    }

Maybe we can add a tiny sleep to avoid waste of CPU resources. For example below，

// code with a tiny sleep
    public void run() {
      while (true) {
        try {
          Thread.sleep(1);
        } catch (InterruptedException e) {
          Thread.currentThread().interrupt();
        }
        for (Map.Entry<DelegationTokenRenewerEvent, Future<?>> entry : futures
            .entrySet()) {
          DelegationTokenRenewerEvent evt = entry.getKey();
... 

Issue Links

• links to: GitHub Pull Request #4465