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Posted to issues@solr.apache.org by "Mark Robert Miller (Jira)" <ji...@apache.org> on 2025/11/06 19:41:00 UTC

[jira] [Commented] (SOLR-17947) CloudSolrClient async state refresh

    [ https://issues.apache.org/jira/browse/SOLR-17947?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18035976#comment-18035976 ] 

Mark Robert Miller commented on SOLR-17947:
-------------------------------------------

Requests that must contact ZooKeeper before proceeding represent a serious SolrCloud anti-pattern. The deeper problem, however, is that all collections share only three global locks. Even with a single collection, when the client operates under high load and needs to refresh cluster state—often unnecessarily for the request to succeed—those locks can become a severe bottleneck. While the state is being fetched, a large number of concurrent requests block on the same lock, and once the state is retrieved, they all resume simultaneously. This burst behavior can amplify load dramatically: a steady 80-requests-per-second pattern at the client can suddenly spike to more than 300 requests per second on the server.

> CloudSolrClient async state refresh
> -----------------------------------
>
>                 Key: SOLR-17947
>                 URL: https://issues.apache.org/jira/browse/SOLR-17947
>             Project: Solr
>          Issue Type: Bug
>    Affects Versions: 9.9
>            Reporter: Mark Robert Miller
>            Priority: Major
>
> * replace striped locks with single-flight cache refresh futures to stop thundering herd
>  * keep stale entries usable while background refresh runs, update retry semantics accordingly



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