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https://issues.apache.org/jira/browse/HBASE-8741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13730397#comment-13730397
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stack commented on HBASE-8741:
------------------------------
Yeah, does not look like it is up on rb. Its 100k.
Is the formatting off here?
{code}
- + "] - WAL is going away");
- return false;
+ + "] - WAL is going away");
+ return false;
}
{code}
Is HLogServices the right name for the Interface that has
obtainRegionsSequenceId? Should it be SequenceIdsService? Or just
SequenceIds? It is HLog that wants the Service, right? It is not a a Service
that HLog is providing?
What else has changed in this patch since previous verions? Thanks H.
It is probably time for someone else to review this one. Any takers? Makes
for nice cleanup of sequenceid reasoning.
> 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
> Attachments: 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
>
>
> 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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