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https://issues.apache.org/jira/browse/HDFS-6772?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arpit Agarwal updated HDFS-6772:
--------------------------------
Summary: Get DN storages out of blockContentsStale state faster after NN
restarts (was: Get DNs out of blockContentsStale==true state faster when NN
restarts)
> Get DN storages out of blockContentsStale state faster after NN restarts
> ------------------------------------------------------------------------
>
> Key: HDFS-6772
> URL: https://issues.apache.org/jira/browse/HDFS-6772
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Ming Ma
> Assignee: Ming Ma
> Attachments: HDFS-6772-2.patch, HDFS-6772-3.patch, HDFS-6772.patch
>
>
> Here is the non-HA scenario.
> 1. Get HDFS into block-over-replicated situation.
> 2. Restart the NN.
> 3. From NN's point of view, DNs will remain in blockContentsStale==true state
> for a long time. That in turns make postponedMisreplicatedBlocks size big.
> Bigger postponedMisreplicatedBlocks size will impact blockreport latency.
> Given blockreport takes NN global lock, it has severe impact on NN
> performance and make the cluster unstable.
> Why will DNs remain in blockContentsStale==true state for a long time?
> 1. When a DN reconnect to NN upon NN restart, blockreport RPC could come in
> before heartbeat RPC. That is due to how BPServiceActor#offerService decides
> when to send blockreport and heartbeat. In the case of NN restart, NN will
> ask DN to register when NN gets the first heartbeat request; DN will then
> register with NN; followed by blockreport RPC; the heartbeat RPC will come
> after that.
> 2. So right after the first blockreport, given heartbeatedSinceFailover
> remains false, blockContentsStale will stay true.
> {noformat}
> DatanodeStorageInfo.java
> void receivedBlockReport() {
> if (heartbeatedSinceFailover) {
> blockContentsStale = false;
> }
> blockReportCount++;
> }
> {noformat}
> 3. So the DN will remain in blockContentsStale==true until the next
> blockreport. For big cluster, dfs.blockreport.intervalMsec could be set to
> some large value.
>
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