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https://issues.apache.org/jira/browse/SOLR-9835?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Cao Manh Dat updated SOLR-9835:
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Attachment: SOLR-9835.patch
Updated patch, change {{boolean onlyLeaderIndexes}} to {{int liveReplicas}}.
{{liveReplicas}} indicate the number of replica ( running on old replication
mode ). If {{liveReplicas = 1}} it will be the same as {{onlyLeaderIndexes =
true}}, all non-leader replicas will fetch latest index from leader. If
{{liveReplicas = -1}} it will be the same as {{onlyLeaderIndexes = false}}.
Right now the valid value for {{liveReplicas}} are 1 and -1.
This will enable the opportunity to configure a cluster with some replicas run
in old mode and some replicas run in new replication mode.
> Create another replication mode for SolrCloud
> ---------------------------------------------
>
> Key: SOLR-9835
> URL: https://issues.apache.org/jira/browse/SOLR-9835
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Reporter: Cao Manh Dat
> Assignee: Shalin Shekhar Mangar
> Attachments: SOLR-9835.patch, SOLR-9835.patch, SOLR-9835.patch,
> SOLR-9835.patch, SOLR-9835.patch, SOLR-9835.patch
>
>
> The current replication mechanism of SolrCloud is called state machine, which
> replicas start in same initial state and for each input, the input is
> distributed across replicas so all replicas will end up with same next state.
> But this type of replication have some drawbacks
> - The commit (which costly) have to run on all replicas
> - Slow recovery, because if replica miss more than N updates on its down
> time, the replica have to download entire index from its leader.
> So we create create another replication mode for SolrCloud called state
> transfer, which acts like master/slave replication. In basically
> - Leader distribute the update to other replicas, but the leader only apply
> the update to IW, other replicas just store the update to UpdateLog (act like
> replication).
> - Replicas frequently polling the latest segments from leader.
> Pros:
> - Lightweight for indexing, because only leader are running the commit,
> updates.
> - Very fast recovery, replicas just have to download the missing segments.
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