[jira] [Commented] (SOLR-16689) Inefficiencies in replication process

["ASF subversion and git services (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-16689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17699697#comment-17699697 ] 

ASF subversion and git services commented on SOLR-16689:
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Commit 44c750a29ecc4ac81562e1e6df501bcbc5ffe39f in solr's branch refs/heads/main from Justin Sweeney
[ https://gitbox.apache.org/repos/asf?p=solr.git;h=44c750a29ec ]

SOLR-16689: Improving efficiency of replication process (#1442)

Improving efficiency of replication process by avoiding repeated attempts to replicate empty index and avoiding commit call to leader when replicating to a non-leader replica

> Inefficiencies in replication process
> -------------------------------------
>
>                 Key: SOLR-16689
>                 URL: https://issues.apache.org/jira/browse/SOLR-16689
>             Project: Solr
>          Issue Type: Improvement
>      Security Level: Public(Default Security Level. Issues are Public) 
>    Affects Versions: 9.1.1
>            Reporter: Justin Sweeney
>            Assignee: Justin Sweeney
>            Priority: Major
>
> There are a couple of inefficiencies with replication that can cause increased CPU usage unnecessarily due to replicas being added:
>  # The [RecoveryStrategy.replicate()|https://github.com/apache/solr/blob/main/solr/core/src/java/org/apache/solr/cloud/RecoveryStrategy.java#L219] method makes a call to commit to on the leader. This happens whenever a replica is reloaded. For PULL replicas in particular this isn't necessary since we can just pull down whatever the latest data is and rely on other mechanisms to be consistently committing the leader. (As an aside, it seems like forcing a commit on the leader might never be necessary, but for this I've limited it to focusing on PULL replicas).
>  # In a case where the leader has no data yet (index version is 0), then a non-leader replica will consistently delete and recreate its core due to this case in IndexFetcher: [https://github.com/apache/solr/blob/main/solr/core/src/java/org/apache/solr/handler/IndexFetcher.java#L549.] This can cause unnecessary CPU usage until the leader has data indexed to it.



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