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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14791) [0.98] CopyTable is extremely slow when moving delete markers
Date Wed, 11 Nov 2015 05:00:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14791?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14999943#comment-14999943
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Lars Hofhansl commented on HBASE-14791:
---------------------------------------

One tricky aspect of this is that we generally want to keep the order of the deletes w.r.t.
puts as much as possible.
If have one buffering mechanism for puts and another for deletes that is hard to maintain.

For correctness it is enough to ensure that deletes are shipped after the puts, not sure that's
easy to do, though.
Then again in cases where we want to ship the deletes, there's better an appropriate setup
on the receiving to keep delete markers around correct, otherwise it makes not sense to ship
them... not maybe not an issue at all?


> [0.98] CopyTable is extremely slow when moving delete markers
> -------------------------------------------------------------
>
>                 Key: HBASE-14791
>                 URL: https://issues.apache.org/jira/browse/HBASE-14791
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.98.16
>            Reporter: Lars Hofhansl
>            Assignee: Alex Araujo
>
> We found that some of our copy table job run for many hours, even when there isn't that
much data to copy.
> [~vik.karma] did his magic and found that the issue is with copying delete markers (we
use raw mode to also move deletes across).
> Looking at the code in 0.98 it's immediately obvious that deletes (unlike puts) are not
batched and hence sent to the other side one by one, causing a network RTT for each delete
marker.
> Looks like in trunk it's doing the right thing (using BufferedMutators for all mutations
in TableOutputFormat). So likely only a 0.98 (and 1.0, 1.1, 1.2?) issue.



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