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https://issues.apache.org/jira/browse/CURATOR-570?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17128706#comment-17128706
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Cam McKenzie commented on CURATOR-570:
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Thanks [~ryarran], seems like it would make sense to modify Curator to have
consistent ordering of clients. Additionally, it is probably worth
preprocessing the connection string provided directly to Curator (rather than
the one returned from Zookeeper), so that if Curator has been supplied
hostnames rather than IP addresses, then we don't get the initial unnecessary
call to updateServerList().
[~randgalt], do you know how this works on the Zookeeper side? I was just
thinking that if the connection string provided to Curator is a list of
hostnames, that storing them as IP addresses rather than resolving them each
time may cause issues with load balancers etc. If ZK resolves the hostnames to
IP addresses anyway though, then we're just delaying the inevitable by not
resolving the hostnames before the initial connection to ZK.
> Excessive calls to ZooKeeper.updateServerList (which can result in session
> death)
> ---------------------------------------------------------------------------------
>
> Key: CURATOR-570
> URL: https://issues.apache.org/jira/browse/CURATOR-570
> Project: Apache Curator
> Issue Type: Bug
> Components: Framework
> Affects Versions: 4.2.0, 4.3.0
> Reporter: Rhys Yarranton
> Priority: Major
>
> On suspend and reconnect, Curator calls ZooKeeper.updateServerList via
> ConnectionState.checkState --> ConnectionState.handleNewConnectionString. In
> addition, recipes may be triggered by this as well, and they too make calls
> ZooKeeper.updateServerList via ConnectState.checkTimeouts -->
> ConnectionState.handleNewConnectionString.
> This happens even though the connection string has not actually changed.
> Due to ZOOKEEPER-3825, this can cause the connection to be closed
> immediately. On its own this would be perceived as a glitch. But due to the
> Curator-induced calls, what we see is a cycle of SUSPENDED/RECONNECTED, until
> eventually the session dies and a new session is recreated.
> Based on the source code (at time of writing), ZooKeeper.updateServerList is
> not intended to be called frequently like this.
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