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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17662) Disable in-memory flush when replaying from WAL
Date Wed, 22 Feb 2017 23:51:44 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17662?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15879490#comment-15879490
] 

stack commented on HBASE-17662:
-------------------------------

bq. Therefore it is acceptable to just skip the in-memory flush action while the updates come
as part of replay from WAL.

IIRC, you would flush during replay when the replayed data was bigger than your memory could
hold....  Turning it off would mess us up. Could you instead take the update lock during replay?

> Disable in-memory flush when replaying from WAL
> -----------------------------------------------
>
>                 Key: HBASE-17662
>                 URL: https://issues.apache.org/jira/browse/HBASE-17662
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Anastasia Braginsky
>            Assignee: Anastasia Braginsky
>         Attachments: HBASE-17662-V02.patch, HBASE-17662-V03.patch, HBASE-17662-V04.patch
>
>
> When replaying the edits from WAL, the region's updateLock is not taken, because a single
threaded action is assumed. However, the thread-safeness of the in-memory flush of CompactingMemStore
is based on taking the region's updateLock. 
> The in-memory flush can be skipped in the replay time (anyway everything is flushed to
disk just after the replay). Therefore it is acceptable to just skip the in-memory flush action
while the updates come as part of replay from WAL.



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