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https://issues.apache.org/jira/browse/HBASE-8741?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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stack updated HBASE-8741:
-------------------------
Resolution: Fixed
Release Note: Sequenceids are now per region rather than per RegionServer.
Hadoop Flags: Reviewed
Status: Resolved (was: Patch Available)
Committed to trunk. Thanks for the nice fixup [~himan...@cloudera.com]
> 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-v6.4.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,
> HBASE-8741-v5.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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