Jason Lowe commented on YARN-3403:

I think the real issue here is the nodemanager is not supposed to be constantly 
re-reading the configuration files.  Normally an explicit refresh admin command 
or restart of the daemon is expected to be performed before daemons recognize 
updated configs.  The problem seems to stem from the fact that 
BCFile.WBlockState is creating a compressor without providing the 
configuration.  When the codec pool gets invoked without a conf it ends up 
creating its own which causes the confs to be read from disk each time.

> Nodemanager dies after a small typo in mapred-site.xml is induced
> -----------------------------------------------------------------
>                 Key: YARN-3403
>                 URL: https://issues.apache.org/jira/browse/YARN-3403
>             Project: Hadoop YARN
>          Issue Type: Bug
>            Reporter: Nikhil Mulley
>            Priority: Critical
> Hi,
> We have noticed that with a small typo in terms of xml config 
> (mapred-site.xml) can cause the nodemanager go down completely without 
> stopping/restarting it externally.
> I find it little weird that editing the config files on the filesystem, could 
> cause the running slave daemon yarn nodemanager shutdown.
> In this case, I had a ending tag '/' missed in a property and that induced 
> the nodemanager go down in a cluster. 
> Why would nodemanager reload the configs while it is running? Are not they 
> picked up when they are started? Even if they are automated to pick up the 
> new configs dynamically, I think the xmllint/config checker should come in 
> before the nodemanager is asked to reload/restart.
> ---
> java.lang.RuntimeException: org.xml.sax.SAXParseException; systemId: 
> file:/etc/hadoop/conf/mapred-site.xml; lineNumber: 228; columnNumber: 3; The 
> element type "value" must be terminated by the matching end-tag "</value>".
>        at 
> org.apache.hadoop.conf.Configuration.loadResource(Configuration.java:2348)
> ---
> Please shed light on this.

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