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From hanm <...@git.apache.org>
Subject [GitHub] zookeeper issue #451: ZOOKEEPER-2184: Zookeeper Client should re-resolve hos...
Date Sat, 26 May 2018 01:00:27 GMT
Github user hanm commented on the issue:

    https://github.com/apache/zookeeper/pull/451
  
    There are also some initial comments about JVM DNS caching
    
    >> Re-resolving at StaticHostProvider level may not be sufficient as InetAddress.getAllByName(String
host) itself uses a Java-level cache inside InetAddress and turns to name service (e.g. DNS)
only if the host could not be found in the Java-level cache.
    
    I think it's a good point that we brought this up - and I think we can't do much here
as there are multiple level of DNS caching not just in JVM but also in OS, switches, etc,
so the best we could do here is to make sure we re-resolve address when necessary, as this
pull request is doing, and meanwhile let user know this might not work in the end due to multiple
level of DNS caching. In that case, I think some links to the Oracle documents about JVM DNS
caching would be helpful so users don't blame ZooKeeper if things don't work, but I think
we can do that documentation update separately after this pull request is merged.


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