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https://issues.apache.org/jira/browse/SOLR-14581?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Eric Pugh updated SOLR-14581:
-----------------------------------
Fix Version/s: 8.7
Resolution: Fixed
Status: Resolved (was: Patch Available)
Fixed via commit 35771c3cfe955c8631755b52cbb5de480285ded9
> Document the way auto commits work in SolrCloud
> -----------------------------------------------
>
> Key: SOLR-14581
> URL: https://issues.apache.org/jira/browse/SOLR-14581
> Project: Solr
> Issue Type: Bug
> Components: documentation, SolrCloud
> Affects Versions: master (9.0)
> Reporter: Bram Van Dam
> Assignee: David Eric Pugh
> Priority: Minor
> Fix For: 8.7
>
> Attachments: SOLR-14581.patch
>
> Time Spent: 1h
> Remaining Estimate: 0h
>
> The documentation is unclear about how auto commits actually work in
> SolrCloud. A mailing list reply by Erick Erickson proved to be enlightening.
> Erick's reply verbatim:
> {quote}Each node has its own timer that starts when it receives an update.
> So in your situation, 60 seconds after any give replica gets it’s first
> update, all documents that have been received in the interval will
> be committed.
> But note several things:
> 1> commits will tend to cluster for a given shard. By that I mean
> they’ll tend to happen within a few milliseconds of each other
> ‘cause it doesn’t take that long for an update to get from the
> leader to all the followers.
> 2> this is per replica. So if you host replicas from multiple collections
> on some node, their commits have no relation to each other. And
> say for some reason you transmit exactly one document that lands
> on shard1. Further, say nodeA contains replicas for shard1 and shard2.
> Only the replica for shard1 would commit.
> 3> Solr promises eventual consistency. In this case, due to all the
> timing variables it is not guaranteed that every replica of a single
> shard has the same document available for search at any given time.
> Say doc1 hits the leader at time T and a follower at time T+10ms.
> Say doc2 hits the leader and gets indexed 5ms before the
> commit is triggered, but for some reason it takes 15ms for it to get
> to the follower. The leader will be able to search doc2, but the
> follower won’t until 60 seconds later.{quote}
> Perhaps the subject deserves a section of its own, but I'll attach a patch
> which includes the gist of Erick's reply as a Tip in the "indexing in
> SolrCloud"-section.
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