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https://issues.apache.org/jira/browse/JAMES-4221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18109818#comment-18109818
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Benoit Tellier commented on JAMES-4221:
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If we'd go that way I'd be also interested by a POC to wrap MailboxMapper with
a REDIS cache...
> Limits of Cassandra counters
> ----------------------------
>
> Key: JAMES-4221
> URL: https://issues.apache.org/jira/browse/JAMES-4221
> Project: James Server
> Issue Type: Improvement
> Reporter: Benoit Tellier
> Priority: Major
>
> h3. Why ?
> I am I think reaching limits of Cassandra counters with a customer.
> They operate a flacky Cassandra cluster causing me tons of headaches with
> COUNTERS being one of them.
> Despite regular runs of Recompute quota we cannot get a converging run onto
> the actual SUM stored in source-of-truth tabled>
> h3. Cassandra counter limits
> - Not idempotent - not our issue here but worth a not - please note that it
> is inherant to the act of counting: in case of error we are stuck under or
> over counting.
> - Not "SET' semantic. We can only add or remove. The Recompute quota above
> does a read-before-write to offset the previous value.
> Inherently the counter stores a set of increments per master nodes - if the
> set of values is inconsistent within the cluster, we take the offset decision
> off a wrong value thus making the count persistently screwed up.
> h3. Alternatives
> Not using counter is not an option as we would be subject to data races.
> LWT usage is out of question for performance reasons.
> h3. Redis design
> Implement a redis cache atop the Read of the data in source of truth table.
> Once coputed this cache is maintained via a mailbox listener by writes.
> We could do this for both:
> - current-quota via a backend-commons implem of the currentQuotaManager
> interface
> - Have an interface defined for mailbox-counters in mailbox-store and in
> mailbox-redis have an implementation of it.
> h3. State of this work
> I'd like to potentially propose a POC to my customer to validate it fixes his
> issues prior merging this upstream.
> Though I am interested by feedback.
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