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https://issues.apache.org/jira/browse/OAK-1453?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas Mueller updated OAK-1453:
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Assignee: (was: Thomas Mueller)
> MongoMK failover support for replica sets (esp. shards)
> -------------------------------------------------------
>
> Key: OAK-1453
> URL: https://issues.apache.org/jira/browse/OAK-1453
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: mongomk
> Reporter: Michael Marth
> Labels: production, resilience
> Fix For: 1.2
>
>
> With OAK-759 we have introduced replica support in MongoMK. I think we still
> need to address the resilience for failover from primary to secoandary:
> Consider a case where Oak writes to the primary. Replication to secondary is
> ongoing. During that period the primary goes down and the secondary becomes
> primary. There could be some "half-replicated" MVCC revisions, which need to
> be either discarded or be ignored after the failover.
> This might not be an issue if there is only one shard, as the commit root is
> written last (and replicated last)
> But with 2 shards the the replication state of these 2 shards could be
> inconsistent. Oak needs to handle such a situation without falling over.
> If we can detect a Mongo failover we could query Mongo which revisions are
> fully replicated to the new primary and discard the potentially
> half-replicated revisions.
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