[jira] [Commented] (HBASE-12437) HLogFactory should be able to accept multiple custom WALReaders in case of failure to read WAL logs due to upgrade/migrate of hbase

["Anoop Sam John (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-12437?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14213681#comment-14213681 ] 

Anoop Sam John commented on HBASE-12437:
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We do write the Writer class name as meta data into WAL files now right? Is it possible to have an association with writer and corresponding reader so that when we read a WAL, we can decide which reader can read this, based on its writer class (?)

> HLogFactory should be able to accept multiple custom WALReaders in case of failure to read WAL logs due to upgrade/migrate of hbase
> -----------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-12437
>                 URL: https://issues.apache.org/jira/browse/HBASE-12437
>             Project: HBase
>          Issue Type: Bug
>          Components: wal
>    Affects Versions: 0.96.0, 0.98.4
>            Reporter: Enoch Hsu
>            Assignee: Enoch Hsu
>             Fix For: 1.0.0, 0.98.4
>
>         Attachments: HBASE_12437.patch
>
>
> The HLogFactory createReader function allows the user to create their own reader and just assumes that the reader will work correctly. 
> The default implementation checks between Protobuf and sequencefiles. However, the custom reader option does not account for any differences in the files. 
> There should be an option or configuration to specify multiple custom readers in the case that an old custom reader was used for sequence files and and a custom reader is being used for protobuf instead of throwing an IPBRE
> The current HLogFactory does not allow me to fall back and handle upgraded file systems similar to the default case.



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