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https://issues.apache.org/jira/browse/HADOOP-16403?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16884346#comment-16884346
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Hadoop QA commented on HADOOP-16403:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue}  0m  
0s{color} | {color:blue} Docker mode activated. {color} |
| {color:red}-1{color} | {color:red} patch {color} | {color:red}  0m  6s{color} 
| {color:red} HADOOP-16403 does not apply to trunk. Rebase required? Wrong 
Branch? See https://wiki.apache.org/hadoop/HowToContribute for help. {color} |
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|| Subsystem || Report/Notes ||
| JIRA Issue | HADOOP-16403 |
| Console output | 
https://builds.apache.org/job/PreCommit-HADOOP-Build/16380/console |
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> Start a new statistical rpc queue and make the Reader's pendingConnection 
> queue runtime-replaceable
> ---------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-16403
>                 URL: https://issues.apache.org/jira/browse/HADOOP-16403
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Jinglun
>            Priority: Major
>         Attachments: HADOOP-16403-How_MetricLinkedBlockingQueue_Works.pdf, 
> HADOOP-16403.001.patch, MetricLinkedBlockingQueueTest.pdf
>
>
> I have an HA cluster with 2 NameNodes. The NameNode's meta is quite big so 
> after the active dead, it takes the standby more than 40s to become active. 
> Many requests(tcp connect request and rpc request) from Datanodes, clients 
> and zkfc timed out and start retrying. The suddenly request flood lasts for 
> the next 2 minutes and finally all requests are either handled or run out of 
> retry times. 
>  Adjusting the rpc related settings might power the NameNode and solve this 
> problem and the key point is finding the bottle neck. The rpc server can be 
> described as below:
> {noformat}
> Listener -> Readers' queues -> Readers -> callQueue -> Handlers{noformat}
> By sampling some failed clients, I find many of them got 
> ConnectTimeoutException. It's caused by a 20s un-responded tcp connect 
> request. I think may be the reader queue is full and block the listener from 
> handling new connections. Both slow handlers and slow readers can block the 
> whole processing progress, and I need to know who it is. I think *a queue 
> that computes the qps, write log when the queue is full and could be replaced 
> easily* will help. 
>  I find the nice work HADOOP-10302 implementing a runtime-swapped queue. 
> Using it at Reader's queue makes the reader queue runtime-swapped 
> automatically. The qps computing job could be done by implementing a subclass 
> of LinkedBlockQueue that does the computing job while put/take/... happens. 
> The qps data will show on jmx.
>  
>  



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