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Posted to dev@zookeeper.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2018/01/26 13:47:00 UTC
***UNCHECKED*** [jira] [Commented] (ZOOKEEPER-2184) Zookeeper Client
should re-resolve hosts when connection attempts fail
[ 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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