Adar Dembo created KUDU-2508:
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Summary: 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
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+yxrlx5...@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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