Xiaoqiao He commented on HDFS-14997:

Ping [~elgoiri],[~sodonnell],[~weichiu] any furthermore comments here?

> BPServiceActor process command from NameNode asynchronously
> -----------------------------------------------------------
>                 Key: HDFS-14997
>                 URL: https://issues.apache.org/jira/browse/HDFS-14997
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>            Reporter: Xiaoqiao He
>            Assignee: Xiaoqiao He
>            Priority: Major
>         Attachments: HDFS-14997.001.patch, HDFS-14997.002.patch, 
> HDFS-14997.003.patch, HDFS-14997.004.patch, HDFS-14997.005.patch
> There are two core functions, report(#sendHeartbeat, #blockReport, 
> #cacheReport) and #processCommand in #BPServiceActor main process flow. If 
> processCommand cost long time it will block send report flow. Meanwhile 
> processCommand could cost long time(over 1000s the worst case I meet) when IO 
> load  of DataNode is very high. Since some IO operations are under 
> #datasetLock, So it has to wait to acquire #datasetLock long time when 
> process some of commands(such as #DNA_INVALIDATE). In such case, #heartbeat 
> will not send to NameNode in-time, and trigger other disasters.
> I propose to improve #processCommand asynchronously and not block 
> #BPServiceActor to send heartbeat back to NameNode when meet high IO load.
> Notes:
> 1. Lifeline could be one effective solution, however some old branches are 
> not support this feature.
> 2. IO operations under #datasetLock is another issue, I think we should solve 
> it at another JIRA.

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