Patrick, could you please elaborate? The Sidecar has been a thing for a while now.
On Mon, Sep 30, 2024 at 7:51 AM Patrick McFadin <pmcfa...@gmail.com> wrote: > I made the mistake of asking two things in one email. > > First thing I asked. Sidecar? Stalled CEP so why is this being talked > about like this is a thing? > > On Mon, Sep 30, 2024 at 7:21 AM Benedict <bened...@apache.org> wrote: > >> Sorry Bernardo, you may have misunderstood me. I don’t have any concerns, >> I was suggesting a possible future scenario where CDC for Kafka via sidecar >> is changed to use a hypothetical future topic subscription service provided >> by C*. It was meant to show that this CEP may be easily decoupled from any >> future evolution in this area. >> >> On 30 Sep 2024, at 14:58, Bernardo Botella <conta...@bernardobotella.com> >> wrote: >> >> Thanks everyone for the comments. >> >> >> Patrick: >> The proposal includes a “best effort” approach for deduplication (some >> details can be found on the Digest class comments on the PR here >> https://github.com/apache/cassandra-analytics/pull/87/files#diff-3a09caecc1da13419d92cde56a7cfc7d253faac08182e6c2768b3d32c015de82R185-R193 >> ). >> That alone won’t eliminate all the duplicates, but as Josh points out, it >> moves the line to something way easier to handle for consumers, and >> definitely on the direction we should aim towards. Accord is definitely >> something this contribution will benefit from, that will move that line >> even further. >> >> Benedict: >> If I understand it correctly, your concern is that Kafka is somewhat the >> hardcoded option for a CDC stream being published? The proposal introduces >> a concept of data sources and sinks ( >> https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=323488575#CEP44:KafkaintegrationforCassandraCDCusingSidecar-SourcesandSinks) >> being kafka the first implemented data sink. That means that the actual >> Kafka output should (will) be something pluggable. >> >> >> >> On Sep 30, 2024, at 5:43 AM, Josh McKenzie <jmcken...@apache.org> wrote: >> >> I don't see much on how this would be handled other than "left to the end >> user to figure out." >> >> My immediate thought when I read that was "Yes. But it's moving where we >> draw the line of 'left to the end user to figure out' *much further* than >> it was before". >> >> This should only be necessary in edge cases w/extended severe degraded >> availability where you can't hit QUORUM w/this design. So we go from >> "De-dupe literally everything o ye' user" to "de-dupe a small fraction of a >> % of the time when things really go off the rails". >> >> It still leaves the burden of processing potential duplicates downstream, >> so some *complexity* burden on the users remains if they have no >> tolerance for processing duplicate messages, however the underlying machine >> resource utilization (from "dedupe everything" to "dedupe a small % of >> things") is pretty massively shifted by this design change. That, and using >> the hash of the mutation the way the extended design does is something a >> downstream consumer could also do on their side to ensure anything that >> came in past the drop-off window wasn't already seen. So not *too* painful; >> certainly a vast improvement over the status quo. >> >> As to TCM and Accord: absolutely agree. I'd love to see a world where we >> Accord everything and fire off CDC to subscribers from a coordinator >> bypassing all this LSM-bastardized post-processing for CDC for instance. >> That said, this is a functionality users needed back in... 2016? When we >> first added CDC. So I think it's worth it to move on it now while retaining >> architectural options to move to updated metadata and transactions as they >> mature (obviously we'll lean on TCM since it's in 5.0 / trunk right now; >> more applies to the accord bit). >> >> On Mon, Sep 30, 2024, at 3:20 AM, Benedict wrote: >> >> >> Yes, with accord it should be fairly easy to have reliable no-dupe log >> streaming without an elected leader. Given the broad set of use cases, I >> can imagine supporting some more native topic subscription API in C* rather >> than requiring Kafka, so perhaps any integration of Kafka with the sidecar >> can be considered a separate parallel effort, that might eventually >> implement itself with this C* feature whenever it materialises? >> >> >> On 30 Sep 2024, at 03:42, Jeff Jirsa <jji...@gmail.com> wrote: >> >> >> >> Transactional metadata and Accord should make it MUCH easier to do >> duplication avoiding CDC (and I was going to note that someone should >> ensure that the interfaces exposed to the public are stable enough not to >> change the published api once those exist) >> >> >> >> On Sep 29, 2024, at 7:04 PM, Patrick McFadin <pmcfa...@gmail.com> wrote: >> >> >> As I was reviewing this, it occurred to me that it was talking about >> Sidecar like it was a thing but that CEP has been stalled for quite some >> time: >> https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=95652224 >> >> If work on this is being done, should we get this official and wrapped up? >> >> On to the proposal... >> >> This has been a topic on the project for over 10 years now. I've seen >> multiple goes at making this work and the issue that always turns out to >> torpedo the project is handing dupes. To the point that they go from a >> generalized Kafka producer engine to something specific to a particular use >> case. I don't see much on how this would be handled other than "left to the >> end user to figure out." >> >> There is also little mention of where the increased resource load would >> be handled. >> >> This has been discussed many times before, but is it time to introduce >> the concept of an elected leader for a token range for this type of >> operation? It would eliminate a ton of problems that need to managed when >> bridging c* to a system like Kafka. Last time it was discussed in earnest >> was for KIP-30: >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-30+-+Allow+for+brokers+to+have+plug-able+consensus+and+meta+data+storage+sub+systems >> >> >> Patrick >> >> On Sat, Sep 28, 2024 at 11:44 AM Jon Haddad <j...@rustyrazorblade.com> >> wrote: >> >> Yes! I’m really looking forward to trying this out. The CEP looks really >> well thought out. I think this will make CDC a lot more useful for a lot of >> teams. >> Jon >> >> >> On Fri, Sep 27, 2024 at 4:23 PM Josh McKenzie <jmcken...@apache.org> >> wrote: >> >> >> Really excited to see this hit the ML James. >> >> As author of the base CDC (get your stones ready for throwing :D) and >> someone moderately involved in the CEP here, definitely welcome any >> questions. CDC is a *thorny* *problem *in a multi-replica distributed >> system like this. >> >> On Fri, Sep 27, 2024, at 5:40 PM, James Berragan wrote: >> >> Hi everyone, >> >> Wiki: >> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-44%3A+Kafka+integration+for+Cassandra+CDC+using+Sidecar >> >> We would like to propose this CEP for adoption by the community. >> >> CDC is a common technique in databases but right now there is no >> out-of-the-box solution to do this easily and at scale with Cassandra. Our >> proposal is to build a fully-fledged solution into the Apache Cassandra >> Sidecar. This comes with a number of benefits: >> - Sidecar is an official part of the existing Cassandra eco-system. >> - Sidecar runs co-located with Cassandra instances and so scales with the >> cluster size. >> - Sidecar can access the underlying Cassandra database to store CDC >> configuration and the CDC state in a special table. >> - Running in the Sidecar does not require additional external resources >> to run. >> >> The core CDC module we anticipate will be pluggable and re-usable, it is >> available for review here: >> https://github.com/apache/cassandra-analytics/pull/87. The remaining >> Sidecar code will follow. >> >> As a reminder, please keep the discussion here on the dev list vs. in the >> wiki, as we’ve found it easier to manage via email. >> >> Sincerely, >> James Berragan >> Bernardo Botella Corbi >> Yifan Cai >> Jyothsna Konisa >> >> >>
