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From "Hari Mankude (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3212) Persist the epoch received by the JournalService
Date Fri, 06 Apr 2012 17:05:23 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3212?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13248498#comment-13248498

Hari Mankude commented on HDFS-3212:

bq.I agree, if you're talking about prefixing it at the beginning of the file, before the
first transaction. But, if you're talking about actually putting it in the content of the
first transaction, I think it's a bad idea for the reason above. 

Todd, if you are referring to creating a edit log with the name format edit_log_<epoch_num>_in_progress
or when finalized edit_log_<epoch_number>_<start_txid>_<end_txid>, it is
a better solution that creating a seperate metadata file. Otherwise, Suresh's solution in
adding the epoch number in start log segment sounds good. Actually, for debugging purposes,
we should add more information such as time when the journal was started, NN id of owner etc
along with epoch number. Basically convert OP_START_LOG_SEGMENT to hold journal header info.

> Persist the epoch received by the JournalService
> ------------------------------------------------
>                 Key: HDFS-3212
>                 URL: https://issues.apache.org/jira/browse/HDFS-3212
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha, name-node
>    Affects Versions: Shared journals (HDFS-3092)
>            Reporter: Suresh Srinivas
> epoch received over JournalProtocol should be persisted by JournalService.

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