Wei-Chiu Chuang created HADOOP-15696:
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Summary: 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
Reporter: Wei-Chiu Chuang
Assignee: Wei-Chiu Chuang
Attachments: 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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