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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:
-------------------------------
Attachment: SOLR-9835.patch
Here a the patch for this issue, I didn't do anything related to Leader
Recovery, just wanna upload the patch soon so anyone can comment first.
- Add {{onlyLeaderIndexes}} property to {{DocCollection}}
- Modified {{SolrIndexWriter#setCommitData(IndexWriter iw, long
commitCommandVersion)}} to store version of commit command to commit point.
- Start replication process to periodically poll latest segments from leader
when replica become active
- Add {{UpdateCommand.IGNORE_INDEXWRITER}} so
+ DistributedUpdateProcessor can look into the role of current core to add
the flag to command
+ DirectUpdateHandler2 based on the existence of {{IGNORE_INDEXWRITER}} to
skip making changes to IW, just write down the updateCommand to its tlog
- Make sure that the current tlog of replicas have all uncommit updates
+ When replication process is complete
+ When replica restart
> 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
> Attachments: 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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