[jira] [Commented] (HADOOP-9640) RPC Congestion Control with FairCallQueue

["Chris Li (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-9640?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13868553#comment-13868553 ] 

Chris Li commented on HADOOP-9640:
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I'd like to get people's thoughts on a new feature: Dynamic reconfiguration

h5. Motivation
1. The tuning of parameters will be important for optimal performance
2. We can recover faster from bad parameters
3. The cost of doing a NN failover to change parameters is too high, while this would be much faster (seconds)

h5. User Interface

Much like `hadoop mradmin -refreshQueueAcls` the user would run the command to reload the CallQueue based on config.


> RPC Congestion Control with FairCallQueue
> -----------------------------------------
>
>                 Key: HADOOP-9640
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9640
>             Project: Hadoop Common
>          Issue Type: Improvement
>    Affects Versions: 3.0.0, 2.2.0
>            Reporter: Xiaobo Peng
>              Labels: hdfs, qos, rpc
>         Attachments: MinorityMajorityPerformance.pdf, NN-denial-of-service-updated-plan.pdf, faircallqueue.patch, faircallqueue2.patch, faircallqueue3.patch, faircallqueue4.patch, faircallqueue5.patch, faircallqueue6.patch, rpc-congestion-control-draft-plan.pdf
>
>
> Several production Hadoop cluster incidents occurred where the Namenode was overloaded and failed to respond. 
> We can improve quality of service for users during namenode peak loads by replacing the FIFO call queue with a [Fair Call Queue|https://issues.apache.org/jira/secure/attachment/12616864/NN-denial-of-service-updated-plan.pdf]. (this plan supersedes rpc-congestion-control-draft-plan).
> Excerpted from the communication of one incident, “The map task of a user was creating huge number of small files in the user directory. Due to the heavy load on NN, the JT also was unable to communicate with NN...The cluster became responsive only once the job was killed.”
> Excerpted from the communication of another incident, “Namenode was overloaded by GetBlockLocation requests (Correction: should be getFileInfo requests. the job had a bug that called getFileInfo for a nonexistent file in an endless loop). All other requests to namenode were also affected by this and hence all jobs slowed down. Cluster almost came to a grinding halt…Eventually killed jobtracker to kill all jobs that are running.”
> Excerpted from HDFS-945, “We've seen defective applications cause havoc on the NameNode, for e.g. by doing 100k+ 'listStatus' on very large directories (60k files) etc.”



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