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https://issues.apache.org/jira/browse/SOLR-14371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17073243#comment-17073243
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Jan Høydahl commented on SOLR-14371:
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[~houston], I wanted to test dynamic reconfiguration with 3 external ZKs like
in the screenshot above. Sadly it does not work, so your assumption in Solr
Operator is wrong - Solr will only maintain a connection to one ZK at a time,
and while the service LB in front of ZK will make sure that Solr will find a
healty ZK, it is not the best way to connect to ZK. Each node should have a
live connection to multiple ZKs at the same time.
I have not investigated why it does not work. Solr uses a new 3.5.x Zk client
library which should have the capability, but probably the way we configure and
use it does not take avantage of this.
When I killed zoo1 in my setup above (which is the one on localhost:2181), Solr
stopped working and was not able to "find" zoo2 or zoo3.
> Zk StatusHandler should know about dynamic zk config
> ----------------------------------------------------
>
> Key: SOLR-14371
> URL: https://issues.apache.org/jira/browse/SOLR-14371
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Reporter: Jan Høydahl
> Assignee: Jan Høydahl
> Priority: Major
> Attachments: dynamic-reconfig.png
>
> Time Spent: 50m
> Remaining Estimate: 0h
>
> With zk 3.5 it supports dynamic reconfig, which is used by the solr-operator
> for Kubernetes. Then Solr is given a zkHost of one url pointing to a LB
> (Service) in front of all zookeepers, and the zkclient will then fetch list
> of all zookeepers from special zknode /zookeeper/config and reconfigure
> itself with connection to all zk nodes listed. So you can then scale up/down
> number of zk nodes dynamically without restarting solr.
> However, the Admin UI displays errors since it believes it is connected to
> only one zk, which is contradictory to what zk itself reports. We need to
> make ZookeeperStatusHandler aware of dynamic reconfig so it asks zkclient
> what current zkHost is instead of relying on Zk_HOST static setting.
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