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From "Shalin Shekhar Mangar (Jira)" <j...@apache.org>
Subject [jira] [Comment Edited] (SOLR-13945) SPLITSHARD data loss due to "rollback"
Date Mon, 25 Nov 2019 04:30:00 GMT

    [ https://issues.apache.org/jira/browse/SOLR-13945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16981287#comment-16981287
] 

Shalin Shekhar Mangar edited comment on SOLR-13945 at 11/25/19 4:29 AM:
------------------------------------------------------------------------

[~ichattopadhyaya] - the final commit was added in SOLR-4997 so that documents are visible
when the sub-shard replicas come up. -It is not necessary if there is a single replica.- (note
it is necessary to call this commit regardless of the replication factor)


was (Author: shalinmangar):
[~ichattopadhyaya] - the final commit was added in SOLR-4997 so that documents are visible
when the sub-shard replicas come up. It is not necessary if there is a single replica.

> SPLITSHARD data loss due to "rollback"
> --------------------------------------
>
>                 Key: SOLR-13945
>                 URL: https://issues.apache.org/jira/browse/SOLR-13945
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>            Reporter: Ishan Chattopadhyaya
>            Priority: Major
>         Attachments: SOLR-13945.patch, SOLR-13945.patch, SOLR-13945.patch
>
>
> # As per SOLR-7673, there is a commit on the parent shard *after state changes* have
happened, i.e. from active/construction/construction to inactive/active/active. Please see
https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/cloud/api/collections/SplitShardCmd.java#L586-L588
> # Due to SOLR-12509, there's now a cleanup/rollback method called "cleanupAfterFailure"
in the finally block that resets the state to active/construction/construction. Please see:
https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/cloud/api/collections/SplitShardCmd.java#L657
> # When 2 is entered into due to a failure in 1, we have a situation where any documents
that went into the subshards (because they are already active by now) are now lost after the
parent becomes active.
> If my above understanding is correct, I am wondering:
> # Why is a commit to parent shard needed *after* the parent shard is inactive, subshards
are now active and the split operation has completed?
> # This rollback looks very suspicious. If state of subshards is already active and parent
is inactive, then what is the need for setting them back to construction? Seems like a crucial
check is missing there. Also, why do we reset the subshard status back to construction instead
of inactive? It is extremely misleading (and, frankly, ridiculous) for any external clusterstate
monitoring tools to see the subshards to go from CONSTRUCTION to ACTIVE to CONSTRUCTION and
then the subshard disappearing.



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