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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject ***UNCHECKED*** [jira] [Commented] (ZOOKEEPER-2184) Zookeeper Client should re-resolve hosts when connection attempts fail
Date Fri, 26 Jan 2018 13:47:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16341073#comment-16341073
] 

ASF GitHub Bot commented on ZOOKEEPER-2184:
-------------------------------------------

Github user mfenes commented on the issue:

    https://github.com/apache/zookeeper/pull/451
  
    Looking at the static initialization block in InetAddressCachePolicy more deeply, the
default TTL is 30 seconds if there is no SecurityManager installed.
    So caching a positive lookup forever in the Java-level cache is the default only if there
is a SecurityManager installed and the TTL is not overridden by "networkaddress.cache.ttl"
to a different value.
    Default caching policy for a negative lookup is 0 (never cache).
    Now the only question is whether 30 seconds default caching is ok or too much for ZK.


> Zookeeper Client should re-resolve hosts when connection attempts fail
> ----------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-2184
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2184
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: java client
>    Affects Versions: 3.4.6, 3.4.7, 3.4.8, 3.4.9, 3.4.10, 3.5.0, 3.5.1, 3.5.2, 3.5.3,
3.4.11
>         Environment: Ubuntu 14.04 host, Docker containers for Zookeeper & Kafka
>            Reporter: Robert P. Thille
>            Assignee: Flavio Junqueira
>            Priority: Blocker
>              Labels: easyfix, patch
>             Fix For: 3.5.4, 3.4.12
>
>         Attachments: ZOOKEEPER-2184.patch
>
>
> Testing in a Docker environment with a single Kafka instance using a single Zookeeper
instance. Restarting the Zookeeper container will cause it to receive a new IP address. Kafka
will never be able to reconnect to Zookeeper and will hang indefinitely. Updating DNS or /etc/hosts
with the new IP address will not help the client to reconnect as the zookeeper/client/StaticHostProvider
resolves the connection string hosts at creation time and never re-resolves.
> A solution would be for the client to notice that connection attempts fail and attempt
to re-resolve the hostnames in the connectString.



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