[jira] [Commented] (SOLR-11478) Solr should remove it's entry from live_nodes in zk immediately on shutdown and add after solr has loaded it's cores and is ready to serve requests.

["Cao Manh Dat (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-11478?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16205397#comment-16205397 ] 

Cao Manh Dat commented on SOLR-11478:
-------------------------------------

For shutdown case, this change makes sense and can easily get done. But for startup cases, this is not trivial and bring little benefit
- When the node startup, it will register all its replicas as DOWN, therefore we do not forward any requests to replicas which have state = DOWN, although /live_nodes entry is already created.
- Replicas will want to receive updates requests when its state = RECOVERING ( but refuse query requests ) on startup, therefore live_nodes entry must already be created.

So advice for anyone is looking at both /live_nodes and state of replica before sending commands to them.

> Solr should remove it's entry from live_nodes in zk immediately on shutdown and add after solr has loaded it's cores and is ready to serve requests.
> ----------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: SOLR-11478
>                 URL: https://issues.apache.org/jira/browse/SOLR-11478
>             Project: Solr
>          Issue Type: Improvement
>      Security Level: Public(Default Security Level. Issues are Public) 
>          Components: SolrCloud
>            Reporter: Binoy Dalal
>            Priority: Minor
>
> Solr currently, upon receiving the stop command, removes its entry from the zk /live_nodes znode after it has finished processing all inflight requests, just before finally shutting down.
> In this case, any applications that depend on a solr node's live_node entry to decide whether or not to query it fail once the stop command has been executed but solr has not yet fully shut down.
> Something similar occurs during startup of a solr node. The solr node seems to add it's entry to the /live_nodes in zk once it is up but before it has started accepting requests and once again, this causes dependent applications to fail in a similar fashion.
> Hence, removal of the node entry and addition of the same to the zk live_nodes immediately upon shutting down and at the very end upon coming up respectively will greatly benefit applications that depend the live_nodes znode.



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