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From "Himanshu Vashishtha (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8741) Scope sequenceid to the region rather than regionserver (WAS: Mutations on Regions in recovery mode might have same sequenceIDs)
Date Sun, 03 Nov 2013 20:32:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13812477#comment-13812477

Himanshu Vashishtha commented on HBASE-8741:

Below are some results I got while testing HLogPE, with threads count varying from 1-5 on
a 5 node (1 NN, 4DN) cluster. 
IMO, the result are mixed and there is almost negligible much perf hit.
for i in `seq 1 5` ; do for j in 1 2 3; do /home/himanshu/hbase-0.97.0-SNAPSHOT/bin/hbase
org.apache.hadoop.hbase.regionserver.wal.HLogPerformanceEvaluation  -verify -threads "${i}"
-iterations 1000000 -nocleanup  -keySize 50 -valueSize 100; done; done

||Threads||w/o patch time||w/o patch ops||w/ patch time||w/ patch ops||

> Scope sequenceid to the region rather than regionserver (WAS: Mutations on Regions in
recovery mode might have same sequenceIDs)
> --------------------------------------------------------------------------------------------------------------------------------
>                 Key: HBASE-8741
>                 URL: https://issues.apache.org/jira/browse/HBASE-8741
>             Project: HBase
>          Issue Type: Bug
>          Components: MTTR
>    Affects Versions: 0.95.1
>            Reporter: Himanshu Vashishtha
>            Assignee: Himanshu Vashishtha
>             Fix For: 0.98.0
>         Attachments: HBASE-8741-trunk-v6.1-rebased.patch, HBASE-8741-trunk-v6.2.1.patch,
HBASE-8741-trunk-v6.2.2.patch, HBASE-8741-trunk-v6.2.2.patch, HBASE-8741-trunk-v6.3.patch,
HBASE-8741-trunk-v6.patch, HBASE-8741-v0.patch, HBASE-8741-v2.patch, HBASE-8741-v3.patch,
HBASE-8741-v4-again.patch, HBASE-8741-v4-again.patch, HBASE-8741-v4.patch, HBASE-8741-v5-again.patch,
> Currently, when opening a region, we find the maximum sequence ID from all its HFiles
and then set the LogSequenceId of the log (in case the later is at a small value). This works
good in recovered.edits case as we are not writing to the region until we have replayed all
of its previous edits. 
> With distributed log replay, if we want to enable writes while a region is under recovery,
we need to make sure that the logSequenceId > maximum logSequenceId of the old regionserver.
Otherwise, we might have a situation where new edits have same (or smaller) sequenceIds. 
> We can store region level information in the WALTrailer, than this scenario could be
avoided by:
> a) reading the trailer of the "last completed" file, i.e., last wal file which has a
trailer and,
> b) completely reading the last wal file (this file would not have the trailer, so it
needs to be read completely).
> In future, if we switch to multi wal file, we could read the trailer for all completed
WAL files, and reading the remaining incomplete files.

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