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From "Ding Yuan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1677) Potential bugs in exception handlers
Date Thu, 13 Feb 2014 13:34:20 GMT

    [ https://issues.apache.org/jira/browse/YARN-1677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13900332#comment-13900332
] 

Ding Yuan commented on YARN-1677:
---------------------------------

Hi, is there anything else I could help for these cases?

> 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
>         Attachments: yarn-1677.patch
>
>
> 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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