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https://issues.apache.org/jira/browse/SOLR-8227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15048224#comment-15048224
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Ishan Chattopadhyaya edited comment on SOLR-8227 at 12/9/15 7:48 AM:
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I think you misunderstand the difference between an update command in the
update log / transaction log (which is passed on during peersync) and a
document in the index. It is guaranteed that after an update is ack'ed by the
leader to the client, the effect would be the same on the indexes across all
replicas (barring bugs). However, it may be possible that the update logs /
transaction logs are different across the replicas (as the commit commands are
not versioned when distributed, so they could be in slightly different points
in time). That would mean not exactly same set of update commands are in the
update log / transaction log for every replica. Does that answer your question?
was (Author: ichattopadhyaya):
I think you misunderstand the difference between an update command in the
update log / transaction log (which is passed on during peersync) and a
document in the index. It is guaranteed that after an update is ack'ed by the
leader to the client, the effect would be the same on the index across all
replicas (barring bugs). However, it may be possible that the update logs /
transaction logs are different across the replicas (as the commit commands are
not versioned when distributed, so they could be in slightly different points
in time). That would mean not exactly same set of update commands are in the
update log / transaction log for every replica. Does that answer your question?
> Recovering replicas should be able to recover from any active replica
> ---------------------------------------------------------------------
>
> Key: SOLR-8227
> URL: https://issues.apache.org/jira/browse/SOLR-8227
> Project: Solr
> Issue Type: Improvement
> Reporter: Varun Thacker
>
> Currently when a replica goes into recovery it uses the leader to recover. It
> first tries to do a PeerSync. If thats not successful it does a
> replication. Most of the times it ends up doing a full replication because
> segment merging, autoCommits causing segments to be formed differently on the
> replicas ( We should explore improving that in another issue ) .
> But when many replicas are recovering and hitting the leader, the leader can
> become a bottleneck. Since Solr is a CP system , we should be able to recover
> from any of the 'active' replicas instead of just the leader.
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