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https://issues.apache.org/jira/browse/HADOOP-15696?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16598091#comment-16598091
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Misha Dmitriev commented on HADOOP-15696:
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[~xiaochen] I agree that any work on connection reusing is more complex and
should be done under another jira.
Can you elaborate on "the connection object is created in relation to the
caller ugi" statement? What's the exact condition for when a connection can be
reused or not?
> KMS performance regression due to too many open file descriptors after Jetty
> migration
> --------------------------------------------------------------------------------------
>
> Key: HADOOP-15696
> URL: https://issues.apache.org/jira/browse/HADOOP-15696
> Project: Hadoop Common
> Issue Type: Bug
> Components: kms
> Affects Versions: 3.0.0-alpha2
> Reporter: Wei-Chiu Chuang
> Assignee: Wei-Chiu Chuang
> Priority: Blocker
> Attachments: HADOOP-15696.001.patch, Screen Shot 2018-08-22 at
> 11.36.16 AM.png, Screen Shot 2018-08-22 at 4.26.51 PM.png, Screen Shot
> 2018-08-22 at 4.26.51 PM.png, Screen Shot 2018-08-22 at 4.27.02 PM.png,
> Screen Shot 2018-08-22 at 4.30.32 PM.png, Screen Shot 2018-08-22 at 4.30.39
> PM.png, Screen Shot 2018-08-24 at 7.08.16 PM.png
>
>
> We recently found KMS performance regressed in Hadoop 3.0, possibly linking
> to the migration from Tomcat to Jetty in HADOOP-13597.
> Symptoms:
> # Hadoop 3.x KMS open file descriptors quickly rises to more than 10 thousand
> under stress, sometimes even exceeds 32K, which is the system limit, causing
> failures for any access to encryption zones. Our internal testing shows the
> openfd number was in the range of a few hundred in Hadoop 2.x, and it
> increases by almost 100x in Hadoop 3.
> # Hadoop 3.x KMS as much as twice the heap size than in Hadoop 2.x. The same
> heap size can go OOM in Hadoop 3.x. Jxray analysis suggests most of them are
> temporary byte arrays associated with open SSL connections.
> # Due to the heap usage, Hadoop 3.x KMS has more frequent GC activities, and
> we observed up to 20% performance reduction due to GC.
> A possible solution is to reduce the idle timeout setting in HttpServer2. It
> is currently hard-coded 10 seconds. By setting it to 1 second, open fds
> dropped from 20 thousand down to 3 thousand in my experiment.
> File this jira to invite open discussion for a solution.
> Credit: [[email protected]] for the proposed Jetty idle timeout remedy;
> [~xiaochen] for digging into this problem.
> Screenshots:
> CDH5 (Hadoop 2) KMS CPU utilization, resident memory and file descriptor
> chart.
> !Screen Shot 2018-08-22 at 4.30.39 PM.png!
> CDH6 (Hadoop 3) KMS CPU utilization, resident memory and file descriptor
> chart.
> !Screen Shot 2018-08-22 at 4.30.32 PM.png!
> CDH5 (Hadoop 2) GC activities on the KMS process
> !Screen Shot 2018-08-22 at 4.26.51 PM.png!
> CDH6 (Hadoop 3) GC activities on the KMS process
> !Screen Shot 2018-08-22 at 4.27.02 PM.png!
> JXray report
> !Screen Shot 2018-08-22 at 11.36.16 AM.png!
> open fd drops from 20 k down to 3k after the proposed change.
> !Screen Shot 2018-08-24 at 7.08.16 PM.png!
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