[jira] [Commented] (SOLR-7347) clock skew can cause data loss

["Yonik Seeley (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-7347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14394574#comment-14394574 ] 

Yonik Seeley commented on SOLR-7347:
------------------------------------

The work in SOLR-7332 may be useful to fix this. 

> clock skew can cause data loss
> ------------------------------
>
>                 Key: SOLR-7347
>                 URL: https://issues.apache.org/jira/browse/SOLR-7347
>             Project: Solr
>          Issue Type: Bug
>          Components: SolrCloud
>            Reporter: Yonik Seeley
>
> The high bits of versions are created using the system clock.
> System clock skew on the order of magnitude of time it takes for one leader to receive it's last update to the time it takes another replica to become a leader can cause data loss for any updates to the same document until the new leaders clock catches up with the old leaders clock.
> 1) replica1 is the leader and indexes document A, choosing version X (and forwards to replicas)
> 2) replica1 goes down
> 3) replica2 becomes the new leader
> 4) replica2 indexes an update for document A, and chooses version Y (which is less than X due to clock skew) and forwards to replica3
> 5) replica3 checks for reordered updates, finds version X and thus drops version Y
> This should be rare... you need a big enough clock skew and updates to the same document with different leaders within that time window.  We should still fix this of course.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

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