[jira] [Resolved] (HDFS-3725) Fix QJM startup when individual JNs have gaps

["Todd Lipcon (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-3725?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Todd Lipcon resolved HDFS-3725.
-------------------------------

       Resolution: Fixed
    Fix Version/s: QuorumJournalManager (HDFS-3077)
     Hadoop Flags: Reviewed

Thanks, committed to branch.
                
> Fix QJM startup when individual JNs have gaps
> ---------------------------------------------
>
>                 Key: HDFS-3725
>                 URL: https://issues.apache.org/jira/browse/HDFS-3725
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha
>    Affects Versions: QuorumJournalManager (HDFS-3077)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>             Fix For: QuorumJournalManager (HDFS-3077)
>
>         Attachments: hdfs-3725.txt
>
>
> This fixes a bug in the HDFS-3077 branch:
> If one of the JNs goes down and comes back up, it may have a discontiguous set of logs in its storage directories. This means that a future {{getEditLogManifest}} call will return a manifest that has gaps - eg it may have txn 1-3 and 7-9 but be missing 4-6. This is OK because it's guaranteed that a quorum of JNs do have those edits elsewhere.
> This situation currently causes an exception since the RemoteEditLogManifest constructor verifies that the returned log files form a contiguous set of edits. That was true for the NameNode but no longer true for this new usage.

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