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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 21:16:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16009511#comment-16009511
] 

Lars Hofhansl commented on HBASE-18027:
---------------------------------------

bq. The worklist handed to HICRE#Replicator can exceed the RPC limit so we break it into separate
RPCs

But how would it do that? That can only happen when the last edit in the batch is huge (so
it would be batch-size-limit + size-of-last-edit). The initial design was for simplicity,
so that only the outer code needs to do any bookkeeping (like progress in ZK).

Lemme look at the patch a little closer. Offhand I'd be more a fan of handling this in the
calling code.

> 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-branch-1.patch, HBASE-18027.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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