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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8497) Protobuf WAL also needs a trailer
Date Mon, 06 May 2013 20:14:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8497?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13650056#comment-13650056
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Sergey Shelukhin commented on HBASE-8497:
-----------------------------------------

We need to be very careful with this, because WAL is not guaranteed to be finished. 
There needs to be some magic at the end of the file, to indicate that WAL is finished, then
trailer size; and around that there needs to be sanity checks in case if magic appears by
coincidence.
And nothing should depend on the trailer necessarily being there, WAL should be replayable
without it.

Also it needs to be done fast, before PB WAL ships, or one would also have to care about backward
compat :)
                
> Protobuf WAL also needs a trailer 
> ----------------------------------
>
>                 Key: HBASE-8497
>                 URL: https://issues.apache.org/jira/browse/HBASE-8497
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Protobufs, wal
>    Affects Versions: 0.95.1
>            Reporter: Enis Soztutar
>             Fix For: 0.98.0, 0.95.1
>
>
> New Protobuf WAL has a header, but we will probably need a trailer as well, reserved
for later usage. 
> Right now, we can we just serialize an empty trailer, but putting more metadata there,
like range of sequence_id's, region names, table names etc might be needed in the future.


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