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https://issues.apache.org/jira/browse/SOLR-15676?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17424592#comment-17424592
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Christine Poerschke commented on SOLR-15676:
--------------------------------------------
We were investigating unexpected and mysterious PeerSync failures.
The failures were correlated with
{code:java}
Requested N updates from ... but retrieved N-x
{code}
INFO logging.
>From log analysis and code reading [~Haddad] suspected that
>{{PeerSync.MissedUpdatesFinderBase.handleVersionsWithRanges}} was returning a
>too high {{totalRequestedVersions}} value due to duplicate versions in the
>inputs and via extra logging we were able to confirm that hypothesis.
* [https://github.com/apache/solr/pull/327] proposes to extend the
{{PeerSyncTest.handleVersionsWithRangesTests()}} added in SOLR-15667 to capture
that behaviour.
[~Haddad] also noticed that the duplicate versions were DBQs i.e. DeleteByQuery
versions.
The PeerSync logic could be revised to more gracefully handle duplicate
versions and/or the RealTimeGetComponent logic could be revised to not return
duplicate versions, but that does not explain how the duplicate versions can
arise so relatively commonly.
It took some detective work but the issue seems to be with the
{{UpdateLog.RecentUpdates.getDeleteByQuery()}} method.
* [https://github.com/apache/solr/pull/328] proposes to add a
{{UpdateLogCloudTest}} to capture the existing behaviour.
As can be seen DBQ updates can be returned twice, this then leads to duplicate
versions in the tlog of the receiving instance and if subsequently the
receiving instance supplies versions to another instance the DBQ version will
be supplied twice.
* [https://github.com/apache/solr/pull/329] (on top of
[https://github.com/apache/solr/pull/328]) proposes to change the
{{UpdateLog.RecentUpdates.getDeleteByQuery}} method so that it does not return
duplicate versions.
> PeerSync failure due to ...
> ---------------------------
>
> Key: SOLR-15676
> URL: https://issues.apache.org/jira/browse/SOLR-15676
> Project: Solr
> Issue Type: Bug
> Reporter: Christine Poerschke
> Assignee: Christine Poerschke
> Priority: Minor
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> details to follow
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