[jira] [Comment Edited] (YARN-4946) RM should write out Aggregated Log Completion file flag next to logs

["Szilard Nemeth (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-4946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16555607#comment-16555607 ] 

Szilard Nemeth edited comment on YARN-4946 at 7/25/18 12:58 PM:
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Hi [~rkanter]!
I'm trying to pick this one up.
Since this is created a long time ago, I suppose RM could work differently regarding "forgotten" applications, e.g. maybe it was improved over time.
Could you please provide me some hints how to test whether RM still forgets applications?
Is it a way to go to have an RM setup with HA, start one application, wait for its completion and do an RM failover or this involves some more complex steps to take?

Could you give me some insights how the application can be "forgotten" if enough time passes, or any other cases that can lead to the same situation?
Thanks!


was (Author: snemeth):
Hi [~rkanter]!
I'm trying to pick this one up.
Since this is created a long time ago, I suppose RM could work differently regarding "forgotten" applications, e.g. maybe it was improved over time.
Could you please provide me some hints how to test whether RM still forgets applications?
Is it a way to go to have an RM setup with HA, start one application, wait for its completion and do an RM failover or this involves some more complex steps to take?
Thanks!

> RM should write out Aggregated Log Completion file flag next to logs
> --------------------------------------------------------------------
>
>                 Key: YARN-4946
>                 URL: https://issues.apache.org/jira/browse/YARN-4946
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: log-aggregation
>    Affects Versions: 2.8.0
>            Reporter: Robert Kanter
>            Assignee: Szilard Nemeth
>            Priority: Major
>
> MAPREDUCE-6415 added a tool that combines the aggregated log files for each Yarn App into a HAR file.  When run, it seeds the list by looking at the aggregated logs directory, and then filters out ineligible apps.  One of the criteria involves checking with the RM that an Application's log aggregation status is not still running and has not failed.  When the RM "forgets" about an older completed Application (e.g. RM failover, enough time has passed, etc), the tool won't find the Application in the RM and will just assume that its log aggregation succeeded, even if it actually failed or is still running.
> We can solve this problem by doing the following:
> # When the RM sees that an Application has successfully finished aggregation its logs, it will write a flag file next to that Application's log files
> # The tool no longer talks to the RM at all.  When looking at the FileSystem, it now uses that flag file to determine if it should process those log files.  If the file is there, it archives, otherwise it does not.
> # As part of the archiving process, it will delete the flag file
> # (If you don't run the tool, the flag file will eventually be cleaned up by the JHS when it cleans up the aggregated logs because it's in the same directory)
> This improvement has several advantages:
> # The edge case about "forgotten" Applications is fixed
> # The tool no longer has to talk to the RM; it only has to consult HDFS.  This is simpler



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