Hi James, great stuff! I hope this set of patches is of the same quality as until-now implementation of Analytics which proved to be quite easy to embed into 3rd party projects which use Analytics as a platform to get data from. I am particularly interested in reusing Avro codecs (translation of InternalRow into its Avro representation) as that opens up a lot of possibilities for further integrations.
I should take a look at the current state of that, definitely something to consider to take a closer look at as the next release of Analytics is due. Regards On Mon, Jan 12, 2026 at 6:54 PM James Berragan <[email protected]> wrote: > > Hello all, > > Just to update everyone about CEP-44 after a period of radio silence. Last > week CASSSIDECAR-243 was merged in, which introduces end-to-end CDC > functionality to the Apache Cassandra Sidecar for the first time. While I'm > sure there will be more features and additions (CASSANDRA-21011 is already in > the works) this marks a major milestone in delivering CEP-44. > > The bulk of the work was completed across the Apache Cassandra Analytics and > Apache Cassandra Sidecar subprojects with the following PRs: > > https://github.com/apache/cassandra-analytics/pull/87 > > https://github.com/apache/cassandra-analytics/pull/99 > > https://github.com/apache/cassandra-analytics/pull/101 > > > https://github.com/apache/cassandra-sidecar/pull/294 > > https://github.com/apache/cassandra-sidecar/pull/147 > > https://github.com/apache/cassandra-sidecar/pull/158 > > https://github.com/apache/cassandra-sidecar/pull/189 > > https://github.com/apache/cassandra-sidecar/pull/193 > > > If you are interested in delving deeper into the code, these are the best > places to start: > > https://github.com/apache/cassandra-analytics/tree/trunk/cassandra-analytics-cdc > - implementation agnostic core CDC module. > > https://github.com/apache/cassandra-analytics/tree/trunk/cassandra-analytics-cdc-sidecar > - CDC implementation using the Sidecar APIs. > > https://github.com/apache/cassandra-analytics/tree/trunk/cassandra-analytics-cdc-codec > - Avro codecs and Kafka integration. > > https://github.com/apache/cassandra-sidecar/tree/trunk/server/src/main/java/org/apache/cassandra/sidecar/cdc > - CDC implementation built into the Apache Cassandra Sidecar. > > > Many thanks and congratulations to Bernardo Botella Corbi, Jyothsna Konisa, > Yifan Cai (apologies if I'm forgetting anyone) for their contributions and > reviews. > > Thanks, > James. > > On Tue, 15 Oct 2024 at 09:57, Bernardo Botella <[email protected]> > wrote: >> >> Hi everyone, >> >> I’d like to make one final round of feedback request for this CEP-44: Kafka >> integration for Cassandra CDC using Sidecar before calling in a vote. We’ll >> leave it open for a few more days, and if nothing else comes in, we will >> call in a vote. >> >> Bernardo >> >> On Oct 1, 2024, at 6:58 AM, James Berragan <[email protected]> wrote: >> >> It seems this has triggered some important discussions about CEP-1 and the >> Sidecar. Let's keep those in their respective threads and focus this >> conversation on CEP-44. >> >> Patrick, I think I missed your point "There is also little mention of where >> the increased resource load would be handled." - you're right, running CDC >> in the Sidecar implicitly means it uses additional resources in the C* >> cluster. This resource usage is proportional to the write throughput, so >> it's not suitable for use cases with very high write throughput, but our >> experience has been that for standard mixed workloads the overhead is >> minimal. The throttling built in safely handles burst workloads. >> >> James. >> >> On Mon, 30 Sept 2024 at 14:22, Josh McKenzie <[email protected]> wrote: >>> >>> This is the type of hidden subproject that will get us into trouble with >>> the board/foundation. I'm sure it's getting enough committer eyeballs, >>> and some PMC oversight, but maybe not enough. >>> >>> I don't agree with the qualifier of it as being hidden. It's definitely >>> lower traffic than the main project but there's movement on the JIRA here: >>> link. >>> >>> I assume the sidecar is going to take longer to reach a tipping point where >>> more people start contributing to it until it has compelling features >>> that'll incentivize folks running their own bespoke sidecars to migrate >>> over. >>> >>> Agree with all your points Jon; there's a lot to be done on it. >>> >>> CEP-1 is pretty much abandoned yeah. I think it'd be reasonable to close it >>> down and open up a new one w/active contributors + active shepherd and a >>> much more limited scope. >>> >>> On Mon, Sep 30, 2024, at 2:13 PM, Patrick McFadin wrote: >>> >>> I'm mentioning it because I was surprised and I feel like I generally have >>> a finger on the pulse of the project. >>> >>> I would love to talk about it more and get more community support and >>> interest. >>> >>> On Mon, Sep 30, 2024 at 11:01 AM Mick Semb Wever <[email protected]> wrote: >>> >>> Agree with Jon, Josh and Patrick here. >>> >>> This is the type of hidden subproject that will get us into trouble with >>> the board/foundation. I'm sure it's getting enough committer eyeballs, >>> and some PMC oversight, but maybe not enough. Addressing the more material >>> points that Jon mentions is the best way to deal with that IMHO. >>> >>> >>> >>> On Mon, 30 Sept 2024 at 20:37, Jon Haddad <[email protected]> wrote: >>> >>> I think it depends on what lens you're looking at the sidecar through. >>> >>> If you're actively working on it, and pulling it into your own infra, sure. >>> It's a thing. >>> >>> If you're an outsider? I have a hard time seeing it. >>> >>> - No documentation as to what it does >>> - No releases >>> - No build instructions >>> - Trying to build using standard gradle commands fails [1] >>> - Included configs don't work out of the box. [2][3] >>> - CEP-1 looks abandonded >>> - The primary reason right now to use it looks to be analytics library, >>> which doesn't work for most teams due to lack of vnode support [4] >>> >>> I think if you were to take a poll of 100 users outside this ML, I'd bet >>> almost every one would agree the sidecar isn't a thing yet, and that's >>> probably more important than if it's actually getting worked on. I think >>> it has quite a ways to go before it looks to be more than an idea that's >>> incubating. >>> >>> [1] https://issues.apache.org/jira/browse/CASSANDRASC-120 >>> [2 https://issues.apache.org/jira/browse/CASSANDRASC-121 >>> [3] https://issues.apache.org/jira/browse/CASSANDRASC-122 >>> [4] https://issues.apache.org/jira/browse/CASSANDRA-19594 >>> >>> >>> On Mon, Sep 30, 2024 at 11:14 AM Josh McKenzie <[email protected]> wrote: >>> >>> >>> The CEP for the sidecar has stalled. The sidecar itself is very much alive >>> and a thing. >>> >>> CEP != artifact. >>> >>> We should definitely clean that up though. >>> >>> On Mon, Sep 30, 2024, at 10:59 AM, Dinesh Joshi wrote: >>> >>> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> >>> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> >>> 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 <[email protected]> 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 >>> >>> >>> >>
