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https://issues.apache.org/jira/browse/HBASE-26347?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xiaolin Ha updated HBASE-26347:
-------------------------------
    External issue ID:   (was: Design doc)

> Support detect and exclude slow DNs in fan-out of WAL
> -----------------------------------------------------
>
>                 Key: HBASE-26347
>                 URL: https://issues.apache.org/jira/browse/HBASE-26347
>             Project: HBase
>          Issue Type: New Feature
>          Components: wal
>    Affects Versions: 2.0.0, 3.0.0-alpha-2
>            Reporter: Xiaolin Ha
>            Assignee: Xiaolin Ha
>            Priority: Major
>
> We all knows the WAL sync performance directly affects the RPC process time.
> And we use self-designed FanOutOneBlockAsyncDFSOutput to sync WAL entries, 
> which connect straightly to all the block located DNs. But when even one DN 
> of the locations is slow, e.g. some disk hardware failures, the WAL syncs 
> slow. And what's more, the hardware failure detected by the lower layer HDFS 
> system is not so sensitive.
> We can detect slow DNs by the ACK time of packets in 
> FanOutOneBlockAsyncDFSOutput, and exclude them when add new blocks after log 
> rolled(rolling log can also be triggered by slow syncs). And shows this info 
> in UI. We can also invalid these excluded DN cache after a duration, to aware 
> the recovery of those DNs. 
> I think this idea can quickly reduce the influence of slow DNs, and improve 
> the service availability.
>  
>  



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