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From "Himanshu Vashishtha (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7006) [MTTR] Improve Region Server Recovery Time - Distributed Log Replay
Date Thu, 06 Jun 2013 19:23:23 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7006?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13677402#comment-13677402

Himanshu Vashishtha commented on HBASE-7006:

Thanks for the above discussion. I have some follow up questions on Option 2/3:

1. If I am reading it correct, Option 2/3 are preserving the sequenceId of the old wal file?
Does that mean the WAL edit created at the new RS for this entry would have old sequenceId?
Or something else?
When a region is opened, it reads the max sequence Ids from its StoreFiles and sets the FSHlog
counter to it (if the counter is at some lower value). If we are keeping the original sequence
IDs, a WAL file could have a random distribution of sequenceIds (would not be tightly ascending
as we have it now). Could there be any gotcha here? Such as handling chain fail-over.

2. Another question is, initially we had one recovered.edits file per WAL; now we planning
one HFile per WAL.
Looking at this, saving on number of I/O (and NN ops) is not that much IMHO as it is the same
number of files as such? With larger number of small files, it could lead to more compaction.
Though stripe compaction could help, but that's a different thing (and I haven't looked at
the compaction code).  Bucketing WALs is definitely better.

> [MTTR] Improve Region Server Recovery Time - Distributed Log Replay
> -------------------------------------------------------------------
>                 Key: HBASE-7006
>                 URL: https://issues.apache.org/jira/browse/HBASE-7006
>             Project: HBase
>          Issue Type: New Feature
>          Components: MTTR
>            Reporter: stack
>            Assignee: Jeffrey Zhong
>            Priority: Critical
>             Fix For: 0.98.0, 0.95.1
>         Attachments: 7006-addendum-3.txt, hbase-7006-addendum.patch, hbase-7006-combined.patch,
hbase-7006-combined-v1.patch, hbase-7006-combined-v4.patch, hbase-7006-combined-v5.patch,
hbase-7006-combined-v6.patch, hbase-7006-combined-v7.patch, hbase-7006-combined-v8.patch,
hbase-7006-combined-v9.patch, LogSplitting Comparison.pdf, ProposaltoimprovelogsplittingprocessregardingtoHBASE-7006-v2.pdf
> Just saw interesting issue where a cluster went down  hard and 30 nodes had 1700 WALs
to replay.  Replay took almost an hour.  It looks like it could run faster that much of the
time is spent zk'ing and nn'ing.
> Putting in 0.96 so it gets a look at least.  Can always punt.

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