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From "Aaron T. Myers (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6440) Support more than 2 NameNodes
Date Fri, 15 May 2015 00:10:02 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14544653#comment-14544653
] 

Aaron T. Myers commented on HDFS-6440:
--------------------------------------

bq. Ah, Ok. Yes, that second set seed will clearly not be used and is definitely be misleading.
Sorry for being dense :-/ I was just looking at the usage of the Random, not the seed!

No sweat. I figured we were talking past each other a bit.

bq. I'm thinking to just pull the better log message up to the static initialization and remove
the those two lines (4-5).

I agree, this seems like the right move to me. Just have a single seed for the whole test
class. Possible that we may at some point encounter some inter-test dependencies, and if so
it'll be nice that there's only a single seed used across all the tests, instead of having
to manually set several seeds to reproduce the same sequence. The fact that we already clearly
log which NN is becoming active should be sufficient for reproducing individual test failures
if one wants to do that.

Thanks, Jesse.

> Support more than 2 NameNodes
> -----------------------------
>
>                 Key: HDFS-6440
>                 URL: https://issues.apache.org/jira/browse/HDFS-6440
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: auto-failover, ha, namenode
>    Affects Versions: 2.4.0
>            Reporter: Jesse Yates
>            Assignee: Jesse Yates
>             Fix For: 3.0.0
>
>         Attachments: Multiple-Standby-NameNodes_V1.pdf, hdfs-6440-cdh-4.5-full.patch,
hdfs-6440-trunk-v1.patch, hdfs-6440-trunk-v1.patch, hdfs-6440-trunk-v3.patch, hdfs-multiple-snn-trunk-v0.patch
>
>
> Most of the work is already done to support more than 2 NameNodes (one active, one standby).
This would be the last bit to support running multiple _standby_ NameNodes; one of the standbys
should be available for fail-over.
> Mostly, this is a matter of updating how we parse configurations, some complexity around
managing the checkpointing, and updating a whole lot of tests.



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