[jira] [Commented] (HBASE-7386) Investigate providing some supervisor support for znode deletion

["Gregory Chanan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-7386?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13535517#comment-13535517 ] 

Gregory Chanan commented on HBASE-7386:
---------------------------------------

I'm going to first tackle the Master case, HBASE-5926.  The proposal is to rip out the script modification of HBASE-5926 and replace with supervisor.d support.  The java code from HBASE-5926 would of course stay, only the restart/cleanup code in the scripts would go.  The goal is to solve the above listed issues:
#2 is solved by running via supervisor (jps reports only one HMaster process when HMaster started via supervisor.d)
#3 is self-evidently solved by running on a real supervisor
#5 is clearly not relevant, as it is only related to the RS.

So, we are left with #1, #4, and #6.
#1 and #6 are solved because the previous script behavior returns when not run in supervisor and supervisor can redirect stdout/stderr when run.
#4 is solved because the old script behavior returns when not run in supervisor and I don't think it makes any sense to run a standalone HBase via supervisor.

Example patch coming soon.
                
> Investigate providing some supervisor support for znode deletion
> ----------------------------------------------------------------
>
>                 Key: HBASE-7386
>                 URL: https://issues.apache.org/jira/browse/HBASE-7386
>             Project: HBase
>          Issue Type: Task
>          Components: master, regionserver, scripts
>            Reporter: Gregory Chanan
>            Assignee: Gregory Chanan
>             Fix For: 0.96.0
>
>
> There a couple of JIRAs for deleting the znode on a process failure:
> HBASE-5844 (RS)
> HBASE-5926 (Master)
> which are pretty neat; on process failure, they delete the znode of the underlying process so HBase can recover faster.
> These JIRAs were implemented via the startup scripts; i.e. the script hangs around and waits for the process to exit, then deletes the znode.
> There are a few problems associated with this approach, as listed in the below JIRAs:
> 1) Hides startup output in script
> https://issues.apache.org/jira/browse/HBASE-5844?focusedCommentId=13463401&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13463401
> 2) two hbase processes listed per launched daemon
> https://issues.apache.org/jira/browse/HBASE-5844?focusedCommentId=13463409&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13463409
> 3) Not run by a real supervisor
> https://issues.apache.org/jira/browse/HBASE-5844?focusedCommentId=13463409&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13463409
> 4) Weird output after kill -9 actual process in standalone mode
> https://issues.apache.org/jira/browse/HBASE-5926?focusedCommentId=13506801&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13506801
> 5) Can kill existing RS if called again
> https://issues.apache.org/jira/browse/HBASE-5844?focusedCommentId=13463401&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13463401
> 6) Hides stdout/stderr[6]
> https://issues.apache.org/jira/browse/HBASE-5844?focusedCommentId=13506832&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13506832
> I suspect running in via something like supervisor.d can solve these issues if we provide the right support.

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