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https://issues.apache.org/jira/browse/HADOOP-15696?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16595865#comment-16595865
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Misha Dmitriev commented on HADOOP-15696:
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I think the KMS client can be improved as follows. The goal is to avoid
creating a TCP connection for each call as done now, but also avoid the
situation when a call is blocked waiting for a connection to become available.
Let's use a {{BlockingQueue}} to store connections for reuse. When some client
thread needs to make a call, it first checks the queue for an available old
connection. If such a connection is available and not closed yet, it's reused
and then stored back in the queue. If no open connection is available, a new
one is created, used and then also stored back in the queue. In this situation
we will normally need no more connection than the maximum number of concurrent
client threads.
> 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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