[
https://issues.apache.org/jira/browse/HDFS-5369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14041484#comment-14041484
]
Lei (Eddy) Xu commented on HDFS-5369:
-------------------------------------
[~andrew.wang] What should be an expected behavior for the negative caching
here? I am currently thinking of a solution that if {{getGroups()}} returns
empty list, we assign a much shorter expiration period for the cached item
(e.g., 30 seconds instead of 4 hours), so that a transient failure might be
handled. Just wondering whether it is realistic in production?
> Support negative caching of user-group mapping
> ----------------------------------------------
>
> Key: HDFS-5369
> URL: https://issues.apache.org/jira/browse/HDFS-5369
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 2.2.0
> Reporter: Andrew Wang
>
> We've seen a situation at a couple of our customers where interactions from
> an unknown user leads to a high-rate of group mapping calls. In one case,
> this was happening at a rate of 450 calls per second with the shell-based
> group mapping, enough to severely impact overall namenode performance and
> also leading to large amounts of log spam (prints a stack trace each time).
> Let's consider negative caching of group mapping, as well as quashing the
> rate of this log message.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
