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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18027) HBaseInterClusterReplicationEndpoint should respect RPC size limits when batching edits
Date Sat, 13 May 2017 04:47:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16009134#comment-16009134
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Lars Hofhansl commented on HBASE-18027:
---------------------------------------

So looking at the code... In the original code I assume that the caller do the size enforcement.
And indeed I see that happening in the code.

{{HBaseInterClusterReplicationEndpoint.replicate}} is called from {{ReplicationSourceWorkerThread.shipEdits}},
which is called from {{ReplicationSourceWorkerThread.run}} after the call to {{ReplicationSourceWorkerThread.readAllEntriesToReplicateOrNextFile}}
which reads the next batch _and_ crucially enforces the replication batch size limit. So any
single batch issued from within {{replicate}} can be larger than the overall batch size enforced
(which defaults to 64MB).

So I don't seen how this cause a problem (but as usually, it is entirely possible that I missed
a piece of the puzzle here)

> HBaseInterClusterReplicationEndpoint should respect RPC size limits when batching edits
> ---------------------------------------------------------------------------------------
>
>                 Key: HBASE-18027
>                 URL: https://issues.apache.org/jira/browse/HBASE-18027
>             Project: HBase
>          Issue Type: Bug
>          Components: Replication
>    Affects Versions: 2.0.0, 1.4.0, 1.3.1
>            Reporter: Andrew Purtell
>            Assignee: Andrew Purtell
>             Fix For: 2.0.0, 1.4.0, 1.3.2
>
>         Attachments: HBASE-18027-branch-1.patch, HBASE-18027.patch, HBASE-18027.patch
>
>
> In HBaseInterClusterReplicationEndpoint#replicate we try to replicate in batches. We
create N lists. N is the minimum of configured replicator threads, number of 100-waledit batches,
or number of current sinks. Every pending entry in the replication context is then placed
in order by hash of encoded region name into one of these N lists. Each of the N lists is
then sent all at once in one replication RPC. We do not test if the sum of data in each N
list will exceed RPC size limits. This code presumes each individual edit is reasonably small.
Not checking for aggregate size while assembling the lists into RPCs is an oversight and can
lead to replication failure when that assumption is violated.
> We can fix this by generating as many replication RPC calls as we need to drain a list,
keeping each RPC under limit, instead of assuming the whole list will fit in one.



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