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https://issues.apache.org/jira/browse/HADOOP-9640?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13881556#comment-13881556
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Daryn Sharp commented on HADOOP-9640:
-------------------------------------
Agreed, this needs subtasks. General comments/requests:
# Please make the default callq a {{BlockingQueue}} again, and have your custom
implementations conform to the interface.
# The default callq should remain a {{LinkedBlockingQueue}}, not a
{{FIFOCallQueue}}. You're doing some pretty tricky locking and I'd rather
trust the JDK.
# Call.getRemoteUser() would be much cleaner to get the UGI than an interface +
enum to get user and group.
# Using the literal string "unknown!" for a user or group is not a good idea.
The more I think about it, multiple queues will exasperate congestion problem
as Kihwal points out. For that reason, I'd like to see minimal invasiveness in
the Server class - I'll feel safe and you are free to experiment with alternate
implementations.
> 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,
> faircallqueue7_with_runtime_swapping.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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