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https://issues.apache.org/jira/browse/JAMES-3407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17229728#comment-17229728
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René Cordier commented on JAMES-3407:
-------------------------------------
https://github.com/linagora/james-project/pull/4013 adds some concurrency
bounding in CassandraMailboxMapper
> Read repair for mailbox denormalisation
> ---------------------------------------
>
> Key: JAMES-3407
> URL: https://issues.apache.org/jira/browse/JAMES-3407
> Project: James Server
> Issue Type: Improvement
> Components: cassandra, mailbox
> Reporter: Benoit Tellier
> Priority: Major
> Fix For: 3.6.0
>
>
> = Why
> Following this ADR https://github.com/apache/james-project/pull/248
> Mailbox inconsistencies requires manual intervention of the admin (via the
> solve-inconsistency webadmin endpoint) to be resolved.
> Having such task to ensure a correct denormalisation state is desirable, but
> optimally we should not have to rely on the admin to remember running it.
> We would prefer an auto-healing solution
> = Context
> Read repair is a classic mechanism in eventual consistent databases (like
> cassandra) to piggy back consistency healing operation upon reads.
> A fraction of the reads will have a wider reach, read more data, and ensure
> it is correctly replicated.
> Cassandra eventual consistency is all about "replication", but
> "denormalization" consistency needs to be handled at the applicative layer.
> In the past we did set up "Solve inconsistency" tasks that can be assimilated
> to Cassandra repairs. In order to achieve denormalization auto-healing, we
> thus needs to implement "applicative read repairs".
> = Technically speaking
> Upon reads, for each mailbox, the mailbox mapper have a configurable random
> chance to trigger read repairs.
> In this case both table are read, and the "solve inconsistency" mechanism is
> applied, if needed.
> Write unit tests demonstrating this "solve inconsistency" behaviour.
> Also read repairs are the missing bit to make the "read only mailboxPath"
> optimization viable: development needs to happen on top of
> https://github.com/linagora/james-project/pull/3635 ` POC Denormalize
> UidValidity as part of MailboxPath projection` branch
> = Definition Of Done
> Record a video :
> - Given a read repair chance of 0.2 (20%)
> - There is a mailbox inconsistency (no OUTBOX) - (remove the mailbox entry
> manually in cassandra)
> - The user does many requests - after some time, the inconsistency is fixed:
> he has an OUTBOX again!
> As an admin, I should be able to configure (or disable) the
> read-repair-chance for the mailbox entity
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