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Posted to issues@kudu.apache.org by "Alex Rodoni (JIRA)" <ji...@apache.org> on 2019/02/15 01:40:00 UTC
[jira] [Commented] (KUDU-2508) nscd should be recommended even when
/etc/hosts is used for name resolution
[ https://issues.apache.org/jira/browse/KUDU-2508?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16768847#comment-16768847 ]
Alex Rodoni commented on KUDU-2508:
-----------------------------------
https://gerrit.cloudera.org/#/c/12493/
> nscd should be recommended even when /etc/hosts is used for name resolution
> ---------------------------------------------------------------------------
>
> Key: KUDU-2508
> URL: https://issues.apache.org/jira/browse/KUDU-2508
> Project: Kudu
> Issue Type: Bug
> Components: documentation
> Affects Versions: n/a
> Reporter: Adar Dembo
> Assignee: Alex Rodoni
> Priority: Major
>
> It's been observed in several clusters in the wild that on old platforms like el6, name resolution can be slow even when /etc/hosts is used. That's because opening /etc/hosts requires the creation of an mmap, which means the kernel has to take mmap_sem for writing, and that can contend with all sorts of other system activity. Furthermore, glibc synchronizes all resolution on a single lock, so there's opportunity for contention there. See [this mailing list post|http://mail-archives.apache.org/mod_mbox/kudu-user/201711.mbox/%3CCADY20s4ePet5gHnqz7HZ13CoY-1SvUNnNOZ8dXrN+YXrLx5TTg@mail.gmail.com%3E] for more details.
> We should document that for better scalability on nodes hosting many replicas, it's best to use nscd to cache this kind of name resolution too.
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