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Marcel Reutegger resolved OAK-1453. ----------------------------------- Resolution: Won't Fix Fix Version/s: (was: 1.6) I'm resolving this issue as WONTFIX because the proposed behaviour is very difficult and complex to implement property, confusing for an API consumer and contradicts what was implemented for OAK-2592 and OAK-3554. The recommended deployment is a replica set with at least three members and a majority write concern. With this setup (even when using shards) a write will only succeed when it is replicated to at least one secondary. This means a successful write operation survives even a primary crash. With this deployment the proposed rollback mechanism in Oak is not needed. Even if such a rollback is desired from a backend POV, the consequences for an Oak or JCR API consumer is rather dangerous and confusing because ACID properties do not hold anymore. > 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 > > 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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)