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From "Tianyin Xu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (YARN-2832) Wrong Check Logic of NodeHealthCheckerService Causes Latent Errors
Date Sat, 08 Nov 2014 03:43:34 GMT

     [ https://issues.apache.org/jira/browse/YARN-2832?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Tianyin Xu updated YARN-2832:
    Summary: Wrong Check Logic of NodeHealthCheckerService Causes Latent Errors  (was: Wrong
Check Logic of  Causes Latent Errors)

> Wrong Check Logic of NodeHealthCheckerService Causes Latent Errors
> ------------------------------------------------------------------
>                 Key: YARN-2832
>                 URL: https://issues.apache.org/jira/browse/YARN-2832
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: nodemanager
>    Affects Versions: 2.4.1, 2.5.1
>         Environment: Any environment
>            Reporter: Tianyin Xu
>         Attachments: health.check.service.1.patch
> NodeManager allows users to specify the health checker script that will be invoked by
the health-checker service via the configuration parameter, "_yarn.nodemanager.health-checker.script.path_"

> During the _serviceInit()_ of the health-check service, NM checks whether the parameter
is set correctly using _shouldRun()_, as follows,
> {code:title=/* NodeHealthCheckerService.java */|borderStyle=solid}
>   protected void serviceInit(Configuration conf) throws Exception {
>     if (NodeHealthScriptRunner.shouldRun(conf)) {
>       nodeHealthScriptRunner = new NodeHealthScriptRunner();
>       addService(nodeHealthScriptRunner);
>     }
>     addService(dirsHandler);
>     super.serviceInit(conf);
>   }
> {code}
> The problem is that if the parameter is misconfigured (e.g., permission problem, wrong
path), NM does not have any log message to inform users which could cause latent errors or
mysterious problems (e.g., "why my scripts does not work?")
> I see the checking and printing logic is put in _serviceStart()_ function in _NodeHealthScriptRunner.java_
(see the following code snippets). However, the logic is very wrong. For an incorrect parameter
that does not pass the "shouldRun" check, _serviceStart()_ would never be called because the
_NodeHealthScriptRunner_ instance does not have the chance to be created (see the code snippets
> {code:title=/* NodeHealthScriptRunner.java */|borderStyle=solid}
>   protected void serviceStart() throws Exception {
>     // if health script path is not configured don't start the thread.
>     if (!shouldRun(conf)) {
>       LOG.info("Not starting node health monitor");
>       return;
>     }
>     ... 
>   }  
> {code}
> Basically, I think the checking and printing logic should be put in the serviceInit()
in NodeHealthCheckerService instead of serviceStart() in NodeHealthScriptRunner.
> See the attachment for the simple patch.

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