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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-18027) Replication should respect RPC size limits when batching edits
Date Mon, 15 May 2017 23:13:04 GMT

     [ https://issues.apache.org/jira/browse/HBASE-18027?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Andrew Purtell updated HBASE-18027:
-----------------------------------
    Attachment: HBASE-18027.patch

Ok, here is a patch that moves the discussed concerns up into the caller(s). This is in response
to feedback from [~lhofhansl]. Although inside HBaseInterClusterReplicationEndpoint the batch
of edits may be broken up into smaller batches for parallelization, up in the callers we can't
see how the sub-batches might be partitioned. So, we have to consider the RPC request limit
with respect to the whole batch, which does simplify the change: If the replication batch
capacity will exceed the RPC request limit we should simply use the RPC request limit as the
replication batch capacity. The downside is this is more pessimistic than if we check limits
right where we are building the sub-batches and know the size of each.

Changes:


- Where we set replicationBatchSizeCapacity in ReplicationSourceWALReaderThread, check if
replicationBatchSizeCapacity will exceed the RPC request size limit, and if so use the request
size limit instead and warn about it with mention of relevant configuration keys.

- When building the current replication batch, check if we will exceed the batch size capacity
_before_ adding an entry to the batch. Ensure at least one entry is added to the batch even
if it means we violate quota or batch size capacity or otherwise replication would become
stuck. 

- WALEntryStream needs a putBack() method to undo next() when we've decided the entry we just
iterated to will cause the batch to exceed size limits.


and minor changes to logging:


- New debug logging in HBaseInterClusterReplicationEndpoint. One new DEBUG level line per
replication batch. 

- Fix trace level log that conflated total amount of data in replication context with size
of data in the worklist submitted as Replicator runnable. 

- Add details to the warning logged if the number of edits replicated is different from the
number received.


All *Replication* unit tests pass with these changes applied.


> Replication 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.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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