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https://issues.apache.org/jira/browse/SOLR-17275?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Smiley updated SOLR-17275:
--------------------------------
Priority: Blocker (was: Major)
> Major performance regression of CloudSolrClient in Solr 9.6.0 when using
> aliases
> --------------------------------------------------------------------------------
>
> Key: SOLR-17275
> URL: https://issues.apache.org/jira/browse/SOLR-17275
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Components: SolrJ
> Affects Versions: 9.6.0
> Environment: SolrJ 9.6.0, Ubuntu 22.04, Java 17
> Reporter: Rafał Harabień
> Priority: Blocker
> Fix For: 9.6.1
>
> Attachments: image-2024-05-06-17-23-42-236.png
>
>
> I observe worse performance of CloudSolrClient after upgrading from SolrJ
> 9.5.0 to 9.6.0, especially on p99.
> p99 jumped from ~25 ms to ~400 ms
> p90 jumped from ~9.9 ms to ~22 ms
> p75 jumped from ~7 ms to ~11 ms
> p50 jumped from ~4.5 ms to ~7.5 ms
> Screenshot from Grafana (at ~14:30 was deployed the new version):
> !image-2024-05-06-17-23-42-236.png!
> I've got a thread-dump and I can see many threads waiting in
> [ZkStateReader.forceUpdateCollection|https://github.com/apache/solr/blob/f8e5a93c11267e13b7b43005a428bfb910ac6e57/solr/solrj-zookeeper/src/java/org/apache/solr/common/cloud/ZkStateReader.java#L503]:
> {noformat}
> Thread info: "suggest-solrThreadPool-thread-52" prio=5 Id=600 BLOCKED on
> org.apache.solr.common.cloud.ZkStateReader@62e6bc3d owned by
> "suggest-solrThreadPool-thread-34" Id=582
> at
> app//org.apache.solr.common.cloud.ZkStateReader.forceUpdateCollection(ZkStateReader.java:506)
> - blocked on org.apache.solr.common.cloud.ZkStateReader@62e6bc3d
> at
> app//org.apache.solr.client.solrj.impl.ZkClientClusterStateProvider.getState(ZkClientClusterStateProvider.java:155)
> at
> app//org.apache.solr.client.solrj.impl.CloudSolrClient.resolveAliases(CloudSolrClient.java:1207)
> at
> app//org.apache.solr.client.solrj.impl.CloudSolrClient.sendRequest(CloudSolrClient.java:1099)
> at
> app//org.apache.solr.client.solrj.impl.CloudSolrClient.requestWithRetryOnStaleState(CloudSolrClient.java:892)
> at
> app//org.apache.solr.client.solrj.impl.CloudSolrClient.request(CloudSolrClient.java:820)
> at
> app//org.apache.solr.client.solrj.SolrRequest.process(SolrRequest.java:255)
> at
> app//org.apache.solr.client.solrj.SolrClient.query(SolrClient.java:927)
> ...
> Number of locked synchronizers = 1
> - java.util.concurrent.ThreadPoolExecutor$Worker@1beb7ed3
> {noformat}
> At the same time qTime from Solr hasn't changed so I'm pretty sure it's a
> client regression.
> I've tried reproducing it locally and I can see
> [forceUpdateCollection|https://github.com/apache/solr/blob/f8e5a93c11267e13b7b43005a428bfb910ac6e57/solr/solrj-zookeeper/src/java/org/apache/solr/common/cloud/ZkStateReader.java#L503]
> function being called for every request in my application. I can see that
> [this|https://github.com/apache/solr/commit/8cf552aa3642be473c6a08ce44feceb9cbe396d7]
> commit
> changed the logic in ZkClientClusterStateProvider.getState so the mentioned
> function gets called if clusterState.getCollectionRef [returns
> null|https://github.com/apache/solr/blob/f8e5a93c11267e13b7b43005a428bfb910ac6e57/solr/solrj-zookeeper/src/java/org/apache/solr/client/solrj/impl/ZkClientClusterStateProvider.java#L151].
> In 9.5.0 it wasn't the case (forceUpdateCollection was not called in this
> place). I can see in the debugger that getCollectionRef only supports
> collections and not aliases (collectionStates map contains only collections).
> In my application all collections are referenced using aliases so I guess
> that's why I can see the regression in Solr response time.
> I am not familiar with the code enough to prepare a PR but I hope this
> insight will be enough to fix this issue.
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