[jira] [Created] (YARN-1677) Potential bugs in exception handlers

["Ding Yuan (JIRA)" <ji...@apache.org>]

Ding Yuan created YARN-1677:
-------------------------------

             Summary: Potential bugs in exception handlers
                 Key: YARN-1677
                 URL: https://issues.apache.org/jira/browse/YARN-1677
             Project: Hadoop YARN
          Issue Type: Bug
          Components: nodemanager
    Affects Versions: 2.2.0
            Reporter: Ding Yuan


Hi Yarn developers,
We are a group of researchers on software reliability, and recently we did a study and found that majority of the most severe failures in hadoop are caused by bugs in exception handling logic. Therefore we built a simple checking tool that automatically detects some bug patterns that have caused some very severe failures. I am reporting some of the results for Yarn here. Any feedback is much appreciated!

==========================
Case 1:
Line: 551, File: "org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainersMonitorImpl.java"

{noformat}
    switch (monitoringEvent.getType()) {
    case START_MONITORING_CONTAINER:
      .. ..
    default:
      // TODO: Wrong event.
    }
{noformat}

The switch fall-through (handling any potential unexpected event) is empty. Should we at least print an error message here?
==========================

==========================
Case 2:
  Line: 491, File: "org/apache/hadoop/yarn/server/nodemanager/NodeStatusUpdaterImpl.java"
{noformat}
          } catch (Throwable e) {

            // TODO Better error handling. Thread can die with the rest of the
            // NM still running.
            LOG.error("Caught exception in status-updater", e);
          }
{noformat}

The handler of this very general exception only logs the error. The TODO seems to indicate it is not sufficient.
==========================

==========================
Case 3:
Line: 861, File: "org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ResourceLocalizationService.java"

   for (LocalResourceStatus stat : remoteResourceStatuses) {
        LocalResource rsrc = stat.getResource();
        LocalResourceRequest req = null;
        try {
          req = new LocalResourceRequest(rsrc);
        } catch (URISyntaxException e) {
          // TODO fail? Already translated several times...
        }

The handler for URISyntaxException is empty, and the TODO seems to indicate it is not sufficient.
The same code pattern can also be found at:
Line: 901, File: "org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ResourceLocalizationService.java"
Line: 838, File: "org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ResourceLocalizationService.java"
Line: 878, File: "org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ResourceLocalizationService.java"
At line: 803, File: org/apache/hadoop/yarn/applications/distributedshell/ApplicationMaster.java, the handler of URISyntaxException also seems not sufficient:
{noformat}
       try {
          shellRsrc.setResource(ConverterUtils.getYarnUrlFromURI(new URI(
              shellScriptPath)));
        } catch (URISyntaxException e) {
          LOG.error("Error when trying to use shell script path specified"
              + " in env, path=" + shellScriptPath);
          e.printStackTrace();

          // A failure scenario on bad input such as invalid shell script path
          // We know we cannot continue launching the container
          // so we should release it.
          // TODO
          numCompletedContainers.incrementAndGet();
          numFailedContainers.incrementAndGet();
          return;
        }
{noformat}
==========================

==========================
Case 4:
Line: 627, File: "org/apache/hadoop/yarn/server/resourcemanager/rmapp/attempt/RMAppAttemptImpl.java"

{noformat}
      try {
        /* keep the master in sync with the state machine */
        this.stateMachine.doTransition(event.getType(), event);
      } catch (InvalidStateTransitonException e) {
        LOG.error("Can't handle this event at current state", e);
        /* TODO fail the application on the failed transition */
      }
{noformat}

The handler of this exception only logs the error. The TODO seems to indicate it is not sufficient.

This exact same code pattern can also be found at:
Line: 573, File: "org/apache/hadoop/yarn/server/resourcemanager/rmapp/RMAppImpl.java"
==========================

==========================
Case 5: empty handler for exception: java.lang.InterruptedException
  Line: 123, File: "org/apache/hadoop/yarn/server/webproxy/WebAppProxy.java"

{noformat}
  public void join() {
    if(proxyServer != null) {
      try {
        proxyServer.join();
      } catch (InterruptedException e) {
      }
    }
  }
{noformat}

The InterruptedException is completely ignored. As a result, any events causing this interrupt will be lost.

More info on why InterruptedException shouldn't be ignored: http://stackoverflow.com/questions/1087475/when-does-javas-thread-sleep-throw-interruptedexception

This pattern of handling InterruptedException can be found in a few other places:
Line: 434, File: org/apache/hadoop/yarn/server/resourcemanager/ResourceManager.java
{noformat}
          try {
            event = eventQueue.take();
          } catch (InterruptedException e) {
            LOG.error("Returning, interrupted : " + e);
            return; // TODO: Kill RM.
          }
{noformat}
Line: 722, File: "org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ResourceLocalizationService.java"
Line: 191, File: "org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainersMonitorImpl.java"
Line: 393, File: "org/apache/hadoop/yarn/util/LinuxResourceCalculatorPlugin.java"
Line: 258, File: "org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/LocalizedResource.java"
==========================

==========================
Case 6: potential divide by zero
line: 581, File: org/apache/hadoop/yarn/server/resourcemanager/scheduler/fifo/FifoScheduler.java
{noformat}
    int availableContainers =
      node.getAvailableResource().getMemory() / capability.getMemory(); // TODO: A buggy
                                                                        // application
                                                                        // with this
                                                                        // zero would
                                                                        // crash the
                                                                        // scheduler.
{noformat}

Should this potential divide by zero be handled?
==========================

==========================
Case 7:
  Line: 260, File: "org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/LocalizedResource.java"
{noformat}
      } catch (YarnException e) {
        // TODO cleanup
        return;
      }
{noformat}

The error handler simply returns without proper clean up.
==========================



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