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https://issues.apache.org/jira/browse/SOLR-17293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18028864#comment-18028864
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Ilan Ginzburg commented on SOLR-17293:
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Thanks for explaining the reasoning. Presence of these queues in ZK implies
running in Overseer mode (and avoiding creating them when running in
distributed mode).
Given there are other conditions to allow defaulting to overseerEnabled=false
(based on Solr version of all live nodes), there are still corner cases to
address (relatively unlikely though): a cluster with no marquer queue directory
present in ZooKeeper is starting. That cluster has nodes in version 10 and
version 9 and it happens a node in version 10 starts first... It will start in
distributed mode, right? Then nodes in version 9 will start and will start
Overseer... This is a recipe to almost certain collection corruption.
Need to make sure once a decision is taken by the first node, it applies to all
nodes.
> Umbrella: Decentralized Cluster Processing as default
> -----------------------------------------------------
>
> Key: SOLR-17293
> URL: https://issues.apache.org/jira/browse/SOLR-17293
> Project: Solr
> Issue Type: Improvement
> Components: SolrCloud
> Reporter: David Smiley
> Priority: Blocker
> Labels: pull-request-available
> Fix For: main (10.0)
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> This is an umbrella issue for tracking work required for running SolrCloud
> with two booleans as default: {{distributedClusterStateUpdates}} and
> {{distributedCollectionConfigSetExecution}}, which we may rename/refactor
> (TBD). When they are set, the Overseer has nothing to do except run "Cluster
> Singleton Plugins" (if you configure any).
> These have been in Solr for years since well before 9.0 and are tested in a
> randomized fashion. But they have not experienced real-world usage to our
> knowledge. There are some scalability concerns, and unclear compatibility
> with PRS.
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