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https://issues.apache.org/jira/browse/JAMES-3623?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Benoit Tellier closed JAMES-3623.
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Resolution: Fixed
Merged
> Multi-datacenter POP3 server product
> ------------------------------------
>
> Key: JAMES-3623
> URL: https://issues.apache.org/jira/browse/JAMES-3623
> Project: James Server
> Issue Type: Improvement
> Components: cassandra, guice, POP3Server
> Reporter: Benoit Tellier
> Priority: Major
> Time Spent: 1h
> Remaining Estimate: 0h
>
> https://www.mail-archive.com/[email protected]/msg70682.html
> we did develop a multi-datacenter friendly
> POP3 server as a derivate of James distributed server.
> It fully avoids lightweight transactions (LWTs) and thus is efficient in
> a multi-datacenter setup.
> The regular James distributed server was a limiting factor: we
> encountered multiple errors linked to Lightweight transaction: read
> timeouts at consistency SERIAL.
> We thus proposed an alternative implementation of the POP3 mailbox,
> based on the messageId backed by a TimeUUID. TimeUUIDs have extremely
> low collision chances and their generation do not require any
> synchronisation. Also, given the POP3 support alone, monotic generation
> of UIDs and MODSEQs is not necessary, and collisions can be tolerated:
> we can thus rely on a random generation strategy. Along with options
> introduced in JAMES-3435 it allows not doing any (LWTs).
> We needed to introduce an additional Cassandra table: given a mailbox,
> list all the messages contained in it by their messageId - size is added
> to the projection for efficiency. This table is maintained via a mailbox
> listener. MessageId is then used for content retrieval and deletion.
> This POP3 implementation had been functionally tested with thunderbird.
> We did furthermore conduct performance tests on top of two datacenters.
> See [1] below as a reference.
> Given that there is traction for such a server (in the medical field a
> lot of people still uses POP3),
> Given the minimal amount of code written,
> Given that we might have one of the first multi-DC friendly MDA of the
> market (POP3 only),
> I propose to create a new distributed-pop3-server leveraging the above
> design.
> TODO:
> - write an ADR to further express the needs and the design,
> - open a Proof Of Concept pull request. It will be based on [2]
> [2] POC @linagora: https://github.com/linagora/james-project/pull/4321
> ---------------------------
> [1] Performance test exercising the distributed multiDC POP3 server
> Infrastructure:
> - 2 DC of 3 Cassandra node each linked via VPN on a link with latencies
> of ~1ms. 2 cores 8 GB for each Cassandra.
> - 4 James nodes of 4 core and 16 GBs
> Testing:
> - Send 100 mail per second during 10 minutes to 80 users
> - Then STAT the mails in POP3
> - Then clean them up (DELE + QUIT)
> Before:
> - The mail processing speed was 73 mail/seconds
> - We noticed 476 SERIAL read timeouts in the logs
> - UID / MODSEQ generation are the top queries upon LocalDelivery (40 ms+ !)
> After:
> - The mail processing speed improved to 85 mail/seconds
> - We did not notice any SERIAL read timeouts in the logs
> - Other cassandra queries did benefit from not co-existing with LWTs
> queries (~ 10% faster)
> - This performance test was conducted without random generation
> strategy UID and MODSEQs. Further enhancements would be expected with
> the exact above proposed design.
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