[jira] [Assigned] (SOLR-14581) Document the way auto commits work in SolrCloud

["David Eric Pugh (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SOLR-14581?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

David Eric Pugh reassigned SOLR-14581:
--------------------------------------

    Assignee: David Eric Pugh

> 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
>         Attachments: SOLR-14581.patch
>
>
> 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.



--
This message was sent by Atlassian Jira
(v8.3.4#803005)

---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscribe@lucene.apache.org
For additional commands, e-mail: issues-help@lucene.apache.org