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https://issues.apache.org/jira/browse/HDFS-11384?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15974123#comment-15974123
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Zhe Zhang commented on HDFS-11384:
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Thanks [~shv], the main logic LGTM. I could not reproduce reported unit test
failures either.
+1 pending a few final comments:
# IIUC, {{BALANCER_NUM_RPC_PER_SEC}} is a best-effort throttling target,
instead of a guaranteed threshold. E.g. it looks possible for
{{Thread.sleep(delay)}} to be interrupted and {{getBlockList}} to be retried in
the while loop. Or the entire {{dispatchBlocks}} call in a thread could die
before {{delay}} seconds, then another {{future\[j\]}} will be issued without
the delay. (Assuming this understanding is correct), I think this is the right
way to handle this logic -- it is a good idea not to optimize for these rare
cases. But can we update the documentation for {{BALANCER_NUM_RPC_PER_SEC}} to
reflect it?
# {{private void dispatchBlocks(long delay) {}} doesn't explain {{delay}} in
its Javadoc.
# What does {{testBalancerRPCDelay}} verify? It is not checking the number of
RPC calls.
> Add option for balancer to disperse getBlocks calls to avoid NameNode's
> rpc.CallQueueLength spike
> -------------------------------------------------------------------------------------------------
>
> Key: HDFS-11384
> URL: https://issues.apache.org/jira/browse/HDFS-11384
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: balancer & mover
> Affects Versions: 2.7.3
> Reporter: yunjiong zhao
> Assignee: yunjiong zhao
> Attachments: balancer.day.png, balancer.week.png,
> HDFS-11384.001.patch, HDFS-11384.002.patch, HDFS-11384.003.patch,
> HDFS-11384.004.patch, HDFS-11384.005.patch
>
>
> When running balancer on hadoop cluster which have more than 3000 Datanodes
> will cause NameNode's rpc.CallQueueLength spike. We observed this situation
> could cause Hbase cluster failure due to RegionServer's WAL timeout.
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