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From "Chao Sun (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-13607) [Edit Tail Fast Path Pt 1] Enhance JournalNode with an in-memory cache of recent edit transactions
Date Tue, 05 Jun 2018 04:23:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-13607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16501275#comment-16501275
] 

Chao Sun commented on HDFS-13607:
---------------------------------

Sounds good [~xkrogen]:

bq. I'm not sure what you mean. If there are multiple layout versions present in the range
of requested transactions, only transactions from the first layout version are returned. That's
what the last line in the while-condition is for. Am I missing anything?

Yes the number of transactions returned by the {{retrieveEdits}} is correct, but the input
{{outputBuffers}} may contain buffers with different versions. The reason I think is that
the condition {{(getLayoutVersionForTxnId(prevTxn) == layoutVersion)}} is triggered *after*
the buffer with different version is added. You can actually verify this with {{testCacheWithMultipleLayoutVersions}}
(after {{assertTxnCountAndContents(1, 50, 5, oldLayout);}}). Not sure if this is an issue
though.


> [Edit Tail Fast Path Pt 1] Enhance JournalNode with an in-memory cache of recent edit
transactions
> --------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-13607
>                 URL: https://issues.apache.org/jira/browse/HDFS-13607
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha, journal-node
>            Reporter: Erik Krogen
>            Assignee: Erik Krogen
>            Priority: Major
>         Attachments: HDFS-13607-HDFS-12943.000.patch, HDFS-13607-HDFS-12943.001.patch,
HDFS-13607-HDFS-12943.002.patch
>
>
> See HDFS-13150 for full design.
> This JIRA is to add the in-memory cache of recent edit transactions on the JournalNode.
This JIRA does not include accesses to this cache.



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