[jira] [Commented] (SOLR-9915) PeerSync alreadyInSync check is not backwards compatible

["ASF subversion and git services (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-9915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15795691#comment-15795691 ] 

ASF subversion and git services commented on SOLR-9915:
-------------------------------------------------------

Commit 5b1f6b2ba48f8afc6c822c097d0500eb2ed66815 in lucene-solr's branch refs/heads/master from [~noble.paul]
[ https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=5b1f6b2 ]

SOLR-9915: PeerSync alreadyInSync check is not backwards compatible and results in full replication during a rolling restart


> PeerSync alreadyInSync check is not backwards compatible
> --------------------------------------------------------
>
>                 Key: SOLR-9915
>                 URL: https://issues.apache.org/jira/browse/SOLR-9915
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>          Components: replication (java)
>    Affects Versions: 6.3
>            Reporter: Tim Owen
>            Assignee: Noble Paul
>            Priority: Blocker
>         Attachments: SOLR-9915.patch
>
>
> The fingerprint check added to PeerSync in SOLR-9446 works fine when all servers are running 6.3 but this means it's hard to do a rolling upgrade from e.g. 6.2.1 to 6.3 because the 6.3 server sends a request to a 6.2.1 server to get a fingerprint and then gets a NPE because the older server doesn't return the expected field in its response.
> This leads to the PeerSync completely failing, and results in a full index replication from scratch, copying all index files over the network. We noticed this happening when we tried to do a rolling upgrade on one of our 6.2.1 clusters to 6.3. Unfortunately this amount of replication was hammering our disks and network, so we had to do a full shutdown, upgrade all to 6.3 and restart, which was not ideal for a production cluster.
> The attached patch should behave more gracefully in this situation, as it will typically return false for alreadyInSync() and then carry on doing the normal re-sync based on versions.



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