Good summary Jakob. WRT to the general purpose vs Kafka-specific, I actually see it slightly differently. Consider how Storm works as an example, there is a data source (spout) which could be Kafka, Database, etc, and then there is a transport (a netty TCP thing iiuc). Storm allows you to process data from any source, but when it comes from a source they always funnel it through their transport to get to the tasks/bolts. It is natural to think of Kafka as the Spout, but I think the better analogy is actually that Kafka is the transport.
It is really hard to make the transport truly pluggable because this is what the tasks interact with and you need to have guarantees about delivery (and reprocessing), partitioning, atomicity of output, ordering, etc so your stream processing can get the right answer. From my point of view what this proposal says is that Kafka would be non-pluggable as the *transport*. So in this proposal data would still come into and out of Kafka from a wide variety of sources, but by requiring Kafka as the transport the interaction with the tasks will always look the same (a persistent, partitioned, log). So going back to the Storm analogy it is something like Spout interface = copy cat Bolt interface = samza This does obviously make Samza dependent on Kafka but it doesn't mean you wouldn't be processing data from all kinds of sources--indeed that is the whole purpose. It just means that each of these data streams would be available as a multi-subscriber Kafka topic to other systems, applications, etc, not just for your job. If you think about how things are now Samza already depends on a partitioned, persistent, offset addressable log with log compaction...which, unsurprisingly, so I don't think this is really a new dependency. Philosophically I think this makes sense too. To make a bunch of programs fit together you have to standardize something. In this proposal what you are standardizing around is really Kafka's protocol for streaming data and your data format. The transformations that connect these streams can be done via Samza, Storm, Spark, standalone java or python programs, etc but the ultimate output and contract to the rest of the organization/world will be the resulting Kafka topic. Philosophically I think this kind of data and protocol based contract is the right way to go rather than saying that the contract is a particular java api and the stream/data is what is pluggable. -Jay On Wed, Jul 8, 2015 at 11:03 AM, Jakob Homan <jgho...@gmail.com> wrote: > Rewinding back to the beginning of this topic, there are effectively > three proposals on the table: > > 1) Chris' ideas for a direction towards a 2.0 release with an emphasis > on API and configuration simplification. This ideas are based on lots > of lessons learned from the 0.x branch and are worthy of a 2.0 label > and breaking backwards compability. I'm not sure I agree with all of > them, but they're definitely worth pursuing. > > 2) Chris' alternative proposal, which goes beyond his first and is > essentially a reboot of Samza to a more limited, entirely > Kafka-focused approach. Samza would cease being a general purpose > stream processing framework, akin to and an alternative to say, Apache > Storm, and would instead become a standalone complement to the Kafka > project. > > 3) Jay's proposal, which goes even further, and suggests that the > Kafka community would be better served by adding stream processing as > a module to Kafka. This is a perfectly valid approach, but since it's > entirely confined to the Kafka project, doesn't really involve Samza. > If the Kafka team were to go this route, there would be no obligation > on the Samza team to shut down, disband, etc. > > This last bit is important because Samza and Kafka, while closely > linked, are distinct communities. The intersection of committers on > both Kafka and Samza is three people out of a combined 18 committers > across both projects. Samza is a distinct community that shares > quite a few users with Kafka, but is able to chart its own course. > > My own view is that Samza has had an amazing year and is taking off at > a rapid rate. It was only proposed for Incubator two years ago and is > still very young. The original team at LinkedIn has left that company > but the project has continued to grow via contributions both from > LinkedIn and from without. We've recently seen a significant uptake > in discussion and bug reports. > > The API, deployment and configuration changes Chris suggests are good > ideas, but I think there is still serious value in having a > stand-alone general stream processing framework that supports other > input sources than Kafka. We've already had contributions for adding > producer support to ElasticSearch and HDFS. As more users come on > board, I would expect them to contribute more consumers and producers. > > It's a bit of chicken-and-the-egg problem; since the original team > didn't have cycles to prioritize support for non-Kafka systems > (kinesis, eventhub, twitter, flume, zeromq, etc.), Samza was less > compelling than other stream processing frameworks that did have > support and was therefore not used in those situations. I'd love to > see those added and the SystemConsumer/Producer APIs improved to > fluently support them as well as Kafka. > Martin had a question regarding the tight coupling between Hadoop HDFS > and MapReduce (and YARN and Common). This has been a problem for > years and there have been several aborted attempts to split the > projects out. Each time there turned out to be a strong need for > cross-cutting collaboration and so the effort was dropped. Absent the > third option above (Kafka adding stream support to itself directly), I > would imagine something similar would play out here. > > We should get a feeling for which of the three proposals the Samza > community is behind, technical details of each notwithstanding. This > would include not just the committers/PMC members, but also the users, > contributors and lurkers. > > -Jakob > > On 8 July 2015 at 07:41, Ben Kirwin <b...@kirw.in> wrote: > > Hi all, > > > > Interesting stuff! Jumping in a bit late, but here goes... > > > > I'd definitely be excited about a slimmed-down and more Kafka-specific > > Samza -- you don't seem to lose much functionality that people > > actually use, and the gains in simplicity / code sharing seem > > potentially very large. (I've spent a bunch of time peeling back those > > layers of abstraction to get eg. more control over message send order, > > and working directly against Kafka's APIs would have been much > > easier.) I also like the approach of letting Kafka code do the heavy > > lifting and letting stream processing systems build on those -- good, > > reusable implementations would be great for the whole > > stream-processing ecosystem, and Samza in particular. > > > > On the other hand, I do hope that using Kafka's group membership / > > partition assignment / etc. stays optional. As far as I can tell, > > ~every major stream processing system that uses Kafka has chosen (or > > switched to) 'static' partitioning, where each logical task consumes a > > fixed set of partitions. When 'dynamic deploying' (a la Storm / Mesos > > / Yarn) the underlying system is already doing failure detection and > > transferring work between hosts when machines go down, so using > > Kafka's implementation is redundant at best -- and at worst, the > > interaction between the two systems can make outages worse. > > > > And thanks to Chris / Jay for getting this ball rolling. Exciting > times... > > > > On Tue, Jul 7, 2015 at 2:35 PM, Jay Kreps <j...@confluent.io> wrote: > >> Hey Roger, > >> > >> I couldn't agree more. We spent a bunch of time talking to people and > that > >> is exactly the stuff we heard time and again. What makes it hard, of > >> course, is that there is some tension between compatibility with what's > >> there now and making things better for new users. > >> > >> I also strongly agree with the importance of multi-language support. We > are > >> talking now about Java, but for application development use cases people > >> want to work in whatever language they are using elsewhere. I think > moving > >> to a model where Kafka itself does the group membership, lifecycle > control, > >> and partition assignment has the advantage of putting all that complex > >> stuff behind a clean api that the clients are already going to be > >> implementing for their consumer, so the added functionality for stream > >> processing beyond a consumer becomes very minor. > >> > >> -Jay > >> > >> On Tue, Jul 7, 2015 at 10:49 AM, Roger Hoover <roger.hoo...@gmail.com> > >> wrote: > >> > >>> Metamorphosis...nice. :) > >>> > >>> This has been a great discussion. As a user of Samza who's recently > >>> integrated it into a relatively large organization, I just want to add > >>> support to a few points already made. > >>> > >>> The biggest hurdles to adoption of Samza as it currently exists that > I've > >>> experienced are: > >>> 1) YARN - YARN is overly complex in many environments where Puppet > would do > >>> just fine but it was the only mechanism to get fault tolerance. > >>> 2) Configuration - I think I like the idea of configuring most of the > job > >>> in code rather than config files. In general, I think the goal should > be > >>> to make it harder to make mistakes, especially of the kind where the > code > >>> expects something and the config doesn't match. The current config is > >>> quite intricate and error-prone. For example, the application logic > may > >>> depend on bootstrapping a topic but rather than asserting that in the > code, > >>> you have to rely on getting the config right. Likewise with serdes, > the > >>> Java representations produced by various serdes (JSON, Avro, etc.) are > not > >>> equivalent so you cannot just reconfigure a serde without changing the > >>> code. It would be nice for jobs to be able to assert what they expect > >>> from their input topics in terms of partitioning. This is getting a > little > >>> off topic but I was even thinking about creating a "Samza config > linter" > >>> that would sanity check a set of configs. Especially in organizations > >>> where config is managed by a different team than the application > developer, > >>> it's very hard to get avoid config mistakes. > >>> 3) Java/Scala centric - for many teams (especially DevOps-type folks), > the > >>> pain of the Java toolchain (maven, slow builds, weak command line > support, > >>> configuration over convention) really inhibits productivity. As more > and > >>> more high-quality clients become available for Kafka, I hope they'll > follow > >>> Samza's model. Not sure how much it affects the proposals in this > thread > >>> but please consider other languages in the ecosystem as well. From > what > >>> I've heard, Spark has more Python users than Java/Scala. > >>> (FYI, we added a Jython wrapper for the Samza API > >>> > >>> > https://github.com/Quantiply/rico/tree/master/jython/src/main/java/com/quantiply/samza > >>> and are working on a Yeoman generator > >>> https://github.com/Quantiply/generator-rico for Jython/Samza projects > to > >>> alleviate some of the pain) > >>> > >>> I also want to underscore Jay's point about improving the user > experience. > >>> That's a very important factor for adoption. I think the goal should > be to > >>> make Samza as easy to get started with as something like Logstash. > >>> Logstash is vastly inferior in terms of capabilities to Samza but it's > easy > >>> to get started and that makes a big difference. > >>> > >>> Cheers, > >>> > >>> Roger > >>> > >>> > >>> > >>> > >>> > >>> On Tue, Jul 7, 2015 at 3:29 AM, Gianmarco De Francisci Morales < > >>> g...@apache.org> wrote: > >>> > >>> > Forgot to add. On the naming issues, Kafka Metamorphosis is a clear > >>> winner > >>> > :) > >>> > > >>> > -- > >>> > Gianmarco > >>> > > >>> > On 7 July 2015 at 13:26, Gianmarco De Francisci Morales < > g...@apache.org > >>> > > >>> > wrote: > >>> > > >>> > > Hi, > >>> > > > >>> > > @Martin, thanks for you comments. > >>> > > Maybe I'm missing some important point, but I think coupling the > >>> releases > >>> > > is actually a *good* thing. > >>> > > To make an example, would it be better if the MR and HDFS > components of > >>> > > Hadoop had different release schedules? > >>> > > > >>> > > Actually, keeping the discussion in a single place would make > agreeing > >>> on > >>> > > releases (and backwards compatibility) much easier, as everybody > would > >>> be > >>> > > responsible for the whole codebase. > >>> > > > >>> > > That said, I like the idea of absorbing samza-core as a > sub-project, > >>> and > >>> > > leave the fancy stuff separate. > >>> > > It probably gives 90% of the benefits we have been discussing here. > >>> > > > >>> > > Cheers, > >>> > > > >>> > > -- > >>> > > Gianmarco > >>> > > > >>> > > On 7 July 2015 at 02:30, Jay Kreps <jay.kr...@gmail.com> wrote: > >>> > > > >>> > >> Hey Martin, > >>> > >> > >>> > >> I agree coupling release schedules is a downside. > >>> > >> > >>> > >> Definitely we can try to solve some of the integration problems in > >>> > >> Confluent Platform or in other distributions. But I think this > ends up > >>> > >> being really shallow. I guess I feel to really get a good user > >>> > experience > >>> > >> the two systems have to kind of feel like part of the same thing > and > >>> you > >>> > >> can't really add that in later--you can put both in the same > >>> > downloadable > >>> > >> tar file but it doesn't really give a very cohesive feeling. I > agree > >>> > that > >>> > >> ultimately any of the project stuff is as much social and naming > as > >>> > >> anything else--theoretically two totally independent projects > could > >>> work > >>> > >> to > >>> > >> tightly align. In practice this seems to be quite difficult > though. > >>> > >> > >>> > >> For the frameworks--totally agree it would be good to maintain the > >>> > >> framework support with the project. In some cases there may not > be too > >>> > >> much > >>> > >> there since the integration gets lighter but I think whatever > stubs > >>> you > >>> > >> need should be included. So no I definitely wasn't trying to imply > >>> > >> dropping > >>> > >> support for these frameworks, just making the integration lighter > by > >>> > >> separating process management from partition management. > >>> > >> > >>> > >> You raise two good points we would have to figure out if we went > down > >>> > the > >>> > >> alignment path: > >>> > >> 1. With respect to the name, yeah I think the first question is > >>> whether > >>> > >> some "re-branding" would be worth it. If so then I think we can > have a > >>> > big > >>> > >> thread on the name. I'm definitely not set on Kafka Streaming or > Kafka > >>> > >> Streams I was just using them to be kind of illustrative. I agree > with > >>> > >> your > >>> > >> critique of these names, though I think people would get the idea. > >>> > >> 2. Yeah you also raise a good point about how to "factor" it. > Here are > >>> > the > >>> > >> options I see (I could get enthusiastic about any of them): > >>> > >> a. One repo for both Kafka and Samza > >>> > >> b. Two repos, retaining the current seperation > >>> > >> c. Two repos, the equivalent of samza-api and samza-core is > >>> absorbed > >>> > >> almost like a third client > >>> > >> > >>> > >> Cheers, > >>> > >> > >>> > >> -Jay > >>> > >> > >>> > >> On Mon, Jul 6, 2015 at 1:18 PM, Martin Kleppmann < > >>> mar...@kleppmann.com> > >>> > >> wrote: > >>> > >> > >>> > >> > Ok, thanks for the clarifications. Just a few follow-up > comments. > >>> > >> > > >>> > >> > - I see the appeal of merging with Kafka or becoming a > subproject: > >>> the > >>> > >> > reasons you mention are good. The risk I see is that release > >>> schedules > >>> > >> > become coupled to each other, which can slow everyone down, and > >>> large > >>> > >> > projects with many contributors are harder to manage. (Jakob, > can > >>> you > >>> > >> speak > >>> > >> > from experience, having seen a wider range of Hadoop ecosystem > >>> > >> projects?) > >>> > >> > > >>> > >> > Some of the goals of a better unified developer experience could > >>> also > >>> > be > >>> > >> > solved by integrating Samza nicely into a Kafka distribution > (such > >>> as > >>> > >> > Confluent's). I'm not against merging projects if we decide > that's > >>> the > >>> > >> way > >>> > >> > to go, just pointing out the same goals can perhaps also be > achieved > >>> > in > >>> > >> > other ways. > >>> > >> > > >>> > >> > - With regard to dropping the YARN dependency: are you proposing > >>> that > >>> > >> > Samza doesn't give any help to people wanting to run on > >>> > >> YARN/Mesos/AWS/etc? > >>> > >> > So the docs would basically have a link to Slider and nothing > else? > >>> Or > >>> > >> > would we maintain integrations with a bunch of popular > deployment > >>> > >> methods > >>> > >> > (e.g. the necessary glue and shell scripts to make Samza work > with > >>> > >> Slider)? > >>> > >> > > >>> > >> > I absolutely think it's a good idea to have the "as a library" > and > >>> > "as a > >>> > >> > process" (using Yi's taxonomy) options for people who want them, > >>> but I > >>> > >> > think there should also be a low-friction path for common "as a > >>> > service" > >>> > >> > deployment methods, for which we probably need to maintain > >>> > integrations. > >>> > >> > > >>> > >> > - Project naming: "Kafka Streams" seems odd to me, because > Kafka is > >>> > all > >>> > >> > about streams already. Perhaps "Kafka Transformers" or "Kafka > >>> Filters" > >>> > >> > would be more apt? > >>> > >> > > >>> > >> > One suggestion: perhaps the core of Samza (stream transformation > >>> with > >>> > >> > state management -- i.e. the "Samza as a library" bit) could > become > >>> > >> part of > >>> > >> > Kafka, while higher-level tools such as streaming SQL and > >>> integrations > >>> > >> with > >>> > >> > deployment frameworks remain in a separate project? In other > words, > >>> > >> Kafka > >>> > >> > would absorb the proven, stable core of Samza, which would > become > >>> the > >>> > >> > "third Kafka client" mentioned early in this thread. The Samza > >>> project > >>> > >> > would then target that third Kafka client as its base API, and > the > >>> > >> project > >>> > >> > would be freed up to explore more experimental new horizons. > >>> > >> > > >>> > >> > Martin > >>> > >> > > >>> > >> > On 6 Jul 2015, at 18:51, Jay Kreps <jay.kr...@gmail.com> wrote: > >>> > >> > > >>> > >> > > Hey Martin, > >>> > >> > > > >>> > >> > > For the YARN/Mesos/etc decoupling I actually don't think it > ties > >>> our > >>> > >> > hands > >>> > >> > > at all, all it does is refactor things. The division of > >>> > >> responsibility is > >>> > >> > > that Samza core is responsible for task lifecycle, state, and > >>> > >> partition > >>> > >> > > management (using the Kafka co-ordinator) but it is NOT > >>> responsible > >>> > >> for > >>> > >> > > packaging, configuration deployment or execution of > processes. The > >>> > >> > problem > >>> > >> > > of packaging and starting these processes is > >>> > >> > > framework/environment-specific. This leaves individual > frameworks > >>> to > >>> > >> be > >>> > >> > as > >>> > >> > > fancy or vanilla as they like. So you can get simple stateless > >>> > >> support in > >>> > >> > > YARN, Mesos, etc using their off-the-shelf app framework > (Slider, > >>> > >> > Marathon, > >>> > >> > > etc). These are well known by people and have nice UIs and a > lot > >>> of > >>> > >> > > flexibility. I don't think they have node affinity as a built > in > >>> > >> option > >>> > >> > > (though I could be wrong). So if we want that we can either > wait > >>> for > >>> > >> them > >>> > >> > > to add it or do a custom framework to add that feature (as > now). > >>> > >> > Obviously > >>> > >> > > if you manage things with old-school ops tools > (puppet/chef/etc) > >>> you > >>> > >> get > >>> > >> > > locality easily. The nice thing, though, is that all the samza > >>> > >> "business > >>> > >> > > logic" around partition management and fault tolerance is in > Samza > >>> > >> core > >>> > >> > so > >>> > >> > > it is shared across frameworks and the framework specific bit > is > >>> > just > >>> > >> > > whether it is smart enough to try to get the same host when a > job > >>> is > >>> > >> > > restarted. > >>> > >> > > > >>> > >> > > With respect to the Kafka-alignment, yeah I think the goal > would > >>> be > >>> > >> (a) > >>> > >> > > actually get better alignment in user experience, and (b) > express > >>> > >> this in > >>> > >> > > the naming and project branding. Specifically: > >>> > >> > > 1. Website/docs, it would be nice for the "transformation" > api to > >>> be > >>> > >> > > discoverable in the main Kafka docs--i.e. be able to explain > when > >>> to > >>> > >> use > >>> > >> > > the consumer and when to use the stream processing > functionality > >>> and > >>> > >> lead > >>> > >> > > people into that experience. > >>> > >> > > 2. Align releases so if you get Kafkza 1.4.2 (or whatever) > that > >>> has > >>> > >> both > >>> > >> > > Kafka and the stream processing part and they actually work > >>> > together. > >>> > >> > > 3. Unify the programming experience so the client and Samza > api > >>> > share > >>> > >> > > config/monitoring/naming/packaging/etc. > >>> > >> > > > >>> > >> > > I think sub-projects keep separate committers and can have a > >>> > separate > >>> > >> > repo, > >>> > >> > > but I'm actually not really sure (I can't find a definition > of a > >>> > >> > subproject > >>> > >> > > in Apache). > >>> > >> > > > >>> > >> > > Basically at a high-level you want the experience to "feel" > like a > >>> > >> single > >>> > >> > > system, not to relatively independent things that are kind of > >>> > >> awkwardly > >>> > >> > > glued together. > >>> > >> > > > >>> > >> > > I think if we did that they having naming or branding like > "kafka > >>> > >> > > streaming" or "kafka streams" or something like that would > >>> actually > >>> > >> do a > >>> > >> > > good job of conveying what it is. I do that this would help > >>> adoption > >>> > >> > quite > >>> > >> > > a lot as it would correctly convey that using Kafka Streaming > with > >>> > >> Kafka > >>> > >> > is > >>> > >> > > a fairly seamless experience and Kafka is pretty heavily > adopted > >>> at > >>> > >> this > >>> > >> > > point. > >>> > >> > > > >>> > >> > > Fwiw we actually considered this model originally when open > >>> sourcing > >>> > >> > Samza, > >>> > >> > > however at that time Kafka was relatively unknown and we > decided > >>> not > >>> > >> to > >>> > >> > do > >>> > >> > > it since we felt it would be limiting. From my point of view > the > >>> > three > >>> > >> > > things have changed (1) Kafka is now really heavily used for > >>> stream > >>> > >> > > processing, (2) we learned that abstracting out the stream > well is > >>> > >> > > basically impossible, (3) we learned it is really hard to > keep the > >>> > two > >>> > >> > > things feeling like a single product. > >>> > >> > > > >>> > >> > > -Jay > >>> > >> > > > >>> > >> > > > >>> > >> > > On Mon, Jul 6, 2015 at 3:37 AM, Martin Kleppmann < > >>> > >> mar...@kleppmann.com> > >>> > >> > > wrote: > >>> > >> > > > >>> > >> > >> Hi all, > >>> > >> > >> > >>> > >> > >> Lots of good thoughts here. > >>> > >> > >> > >>> > >> > >> I agree with the general philosophy of tying Samza more > firmly to > >>> > >> Kafka. > >>> > >> > >> After I spent a while looking at integrating other message > >>> brokers > >>> > >> (e.g. > >>> > >> > >> Kinesis) with SystemConsumer, I came to the conclusion that > >>> > >> > SystemConsumer > >>> > >> > >> tacitly assumes a model so much like Kafka's that pretty much > >>> > nobody > >>> > >> but > >>> > >> > >> Kafka actually implements it. (Databus is perhaps an > exception, > >>> but > >>> > >> it > >>> > >> > >> isn't widely used outside of LinkedIn.) Thus, making Samza > fully > >>> > >> > dependent > >>> > >> > >> on Kafka acknowledges that the system-independence was never > as > >>> > real > >>> > >> as > >>> > >> > we > >>> > >> > >> perhaps made it out to be. The gains of code reuse are real. > >>> > >> > >> > >>> > >> > >> The idea of decoupling Samza from YARN has also always been > >>> > >> appealing to > >>> > >> > >> me, for various reasons already mentioned in this thread. > >>> Although > >>> > >> > making > >>> > >> > >> Samza jobs deployable on anything (YARN/Mesos/AWS/etc) seems > >>> > >> laudable, > >>> > >> > I am > >>> > >> > >> a little concerned that it will restrict us to a lowest > common > >>> > >> > denominator. > >>> > >> > >> For example, would host affinity (SAMZA-617) still be > possible? > >>> For > >>> > >> jobs > >>> > >> > >> with large amounts of state, I think SAMZA-617 would be a big > >>> boon, > >>> > >> > since > >>> > >> > >> restoring state off the changelog on every single restart is > >>> > painful, > >>> > >> > due > >>> > >> > >> to long recovery times. It would be a shame if the decoupling > >>> from > >>> > >> YARN > >>> > >> > >> made host affinity impossible. > >>> > >> > >> > >>> > >> > >> Jay, a question about the proposed API for instantiating a > job in > >>> > >> code > >>> > >> > >> (rather than a properties file): when submitting a job to a > >>> > cluster, > >>> > >> is > >>> > >> > the > >>> > >> > >> idea that the instantiation code runs on a client somewhere, > >>> which > >>> > >> then > >>> > >> > >> pokes the necessary endpoints on YARN/Mesos/AWS/etc? Or does > that > >>> > >> code > >>> > >> > run > >>> > >> > >> on each container that is part of the job (in which case, how > >>> does > >>> > >> the > >>> > >> > job > >>> > >> > >> submission to the cluster work)? > >>> > >> > >> > >>> > >> > >> I agree with Garry that it doesn't feel right to make a 1.0 > >>> release > >>> > >> > with a > >>> > >> > >> plan for it to be immediately obsolete. So if this is going > to > >>> > >> happen, I > >>> > >> > >> think it would be more honest to stick with 0.* version > numbers > >>> > until > >>> > >> > the > >>> > >> > >> library-ified Samza has been implemented, is stable and > widely > >>> > used. > >>> > >> > >> > >>> > >> > >> Should the new Samza be a subproject of Kafka? There is > precedent > >>> > for > >>> > >> > >> tight coupling between different Apache projects (e.g. > Curator > >>> and > >>> > >> > >> Zookeeper, or Slider and YARN), so I think remaining separate > >>> would > >>> > >> be > >>> > >> > ok. > >>> > >> > >> Even if Samza is fully dependent on Kafka, there is enough > >>> > substance > >>> > >> in > >>> > >> > >> Samza that it warrants being a separate project. An argument > in > >>> > >> favour > >>> > >> > of > >>> > >> > >> merging would be if we think Kafka has a much stronger "brand > >>> > >> presence" > >>> > >> > >> than Samza; I'm ambivalent on that one. If the Kafka project > is > >>> > >> willing > >>> > >> > to > >>> > >> > >> endorse Samza as the "official" way of doing stateful stream > >>> > >> > >> transformations, that would probably have much the same > effect as > >>> > >> > >> re-branding Samza as "Kafka Stream Processors" or suchlike. > Close > >>> > >> > >> collaboration between the two projects will be needed in any > >>> case. > >>> > >> > >> > >>> > >> > >> From a project management perspective, I guess the "new > Samza" > >>> > would > >>> > >> > have > >>> > >> > >> to be developed on a branch alongside ongoing maintenance of > the > >>> > >> current > >>> > >> > >> line of development? I think it would be important to > continue > >>> > >> > supporting > >>> > >> > >> existing users, and provide a graceful migration path to the > new > >>> > >> > version. > >>> > >> > >> Leaving the current versions unsupported and forcing people > to > >>> > >> rewrite > >>> > >> > >> their jobs would send a bad signal. > >>> > >> > >> > >>> > >> > >> Best, > >>> > >> > >> Martin > >>> > >> > >> > >>> > >> > >> On 2 Jul 2015, at 16:59, Jay Kreps <j...@confluent.io> wrote: > >>> > >> > >> > >>> > >> > >>> Hey Garry, > >>> > >> > >>> > >>> > >> > >>> Yeah that's super frustrating. I'd be happy to chat more > about > >>> > this > >>> > >> if > >>> > >> > >>> you'd be interested. I think Chris and I started with the > idea > >>> of > >>> > >> "what > >>> > >> > >>> would it take to make Samza a kick-ass ingestion tool" but > >>> > >> ultimately > >>> > >> > we > >>> > >> > >>> kind of came around to the idea that ingestion and > >>> transformation > >>> > >> had > >>> > >> > >>> pretty different needs and coupling the two made things > hard. > >>> > >> > >>> > >>> > >> > >>> For what it's worth I think copycat (KIP-26) actually will > do > >>> what > >>> > >> you > >>> > >> > >> are > >>> > >> > >>> looking for. > >>> > >> > >>> > >>> > >> > >>> With regard to your point about slider, I don't necessarily > >>> > >> disagree. > >>> > >> > >> But I > >>> > >> > >>> think getting good YARN support is quite doable and I think > we > >>> can > >>> > >> make > >>> > >> > >>> that work well. I think the issue this proposal solves is > that > >>> > >> > >> technically > >>> > >> > >>> it is pretty hard to support multiple cluster management > systems > >>> > the > >>> > >> > way > >>> > >> > >>> things are now, you need to write an "app master" or > "framework" > >>> > for > >>> > >> > each > >>> > >> > >>> and they are all a little different so testing is really > hard. > >>> In > >>> > >> the > >>> > >> > >>> absence of this we have been stuck with just YARN which has > >>> > >> fantastic > >>> > >> > >>> penetration in the Hadoopy part of the org, but zero > penetration > >>> > >> > >> elsewhere. > >>> > >> > >>> Given the huge amount of work being put in to slider, > marathon, > >>> > aws > >>> > >> > >>> tooling, not to mention the umpteen related packaging > >>> technologies > >>> > >> > people > >>> > >> > >>> want to use (Docker, Kubernetes, various cloud-specific > deploy > >>> > >> tools, > >>> > >> > >> etc) > >>> > >> > >>> I really think it is important to get this right. > >>> > >> > >>> > >>> > >> > >>> -Jay > >>> > >> > >>> > >>> > >> > >>> On Thu, Jul 2, 2015 at 4:17 AM, Garry Turkington < > >>> > >> > >>> g.turking...@improvedigital.com> wrote: > >>> > >> > >>> > >>> > >> > >>>> Hi all, > >>> > >> > >>>> > >>> > >> > >>>> I think the question below re does Samza become a > sub-project > >>> of > >>> > >> Kafka > >>> > >> > >>>> highlights the broader point around migration. Chris > mentions > >>> > >> Samza's > >>> > >> > >>>> maturity is heading towards a v1 release but I'm not sure > it > >>> > feels > >>> > >> > >> right to > >>> > >> > >>>> launch a v1 then immediately plan to deprecate most of it. > >>> > >> > >>>> > >>> > >> > >>>> From a selfish perspective I have some guys who have > started > >>> > >> working > >>> > >> > >> with > >>> > >> > >>>> Samza and building some new consumers/producers was next > up. > >>> > Sounds > >>> > >> > like > >>> > >> > >>>> that is absolutely not the direction to go. I need to look > into > >>> > the > >>> > >> > KIP > >>> > >> > >> in > >>> > >> > >>>> more detail but for me the attractiveness of adding new > Samza > >>> > >> > >>>> consumer/producers -- even if yes all they were doing was > >>> really > >>> > >> > getting > >>> > >> > >>>> data into and out of Kafka -- was to avoid having to > worry > >>> > about > >>> > >> the > >>> > >> > >>>> lifecycle management of external clients. If there is a > generic > >>> > >> Kafka > >>> > >> > >>>> ingress/egress layer that I can plug a new connector into > and > >>> > have > >>> > >> a > >>> > >> > >> lot of > >>> > >> > >>>> the heavy lifting re scale and reliability done for me > then it > >>> > >> gives > >>> > >> > me > >>> > >> > >> all > >>> > >> > >>>> the pushing new consumers/producers would. If not then it > >>> > >> complicates > >>> > >> > my > >>> > >> > >>>> operational deployments. > >>> > >> > >>>> > >>> > >> > >>>> Which is similar to my other question with the proposal -- > if > >>> we > >>> > >> > build a > >>> > >> > >>>> fully available/stand-alone Samza plus the requisite shims > to > >>> > >> > integrate > >>> > >> > >>>> with Slider etc I suspect the former may be a lot more work > >>> than > >>> > we > >>> > >> > >> think. > >>> > >> > >>>> We may make it much easier for a newcomer to get something > >>> > running > >>> > >> but > >>> > >> > >>>> having them step up and get a reliable production > deployment > >>> may > >>> > >> still > >>> > >> > >>>> dominate mailing list traffic, if for different reasons > than > >>> > >> today. > >>> > >> > >>>> > >>> > >> > >>>> Don't get me wrong -- I'm comfortable with making the Samza > >>> > >> dependency > >>> > >> > >> on > >>> > >> > >>>> Kafka much more explicit and I absolutely see the > benefits in > >>> > the > >>> > >> > >>>> reduction of duplication and clashing > >>> terminologies/abstractions > >>> > >> that > >>> > >> > >>>> Chris/Jay describe. Samza as a library would likely be a > very > >>> > nice > >>> > >> > tool > >>> > >> > >> to > >>> > >> > >>>> add to the Kafka ecosystem. I just have the concerns above > re > >>> the > >>> > >> > >>>> operational side. > >>> > >> > >>>> > >>> > >> > >>>> Garry > >>> > >> > >>>> > >>> > >> > >>>> -----Original Message----- > >>> > >> > >>>> From: Gianmarco De Francisci Morales [mailto: > g...@apache.org] > >>> > >> > >>>> Sent: 02 July 2015 12:56 > >>> > >> > >>>> To: dev@samza.apache.org > >>> > >> > >>>> Subject: Re: Thoughts and obesrvations on Samza > >>> > >> > >>>> > >>> > >> > >>>> Very interesting thoughts. > >>> > >> > >>>> From outside, I have always perceived Samza as a computing > >>> layer > >>> > >> over > >>> > >> > >>>> Kafka. > >>> > >> > >>>> > >>> > >> > >>>> The question, maybe a bit provocative, is "should Samza be > a > >>> > >> > sub-project > >>> > >> > >>>> of Kafka then?" > >>> > >> > >>>> Or does it make sense to keep it as a separate project > with a > >>> > >> separate > >>> > >> > >>>> governance? > >>> > >> > >>>> > >>> > >> > >>>> Cheers, > >>> > >> > >>>> > >>> > >> > >>>> -- > >>> > >> > >>>> Gianmarco > >>> > >> > >>>> > >>> > >> > >>>> On 2 July 2015 at 08:59, Yan Fang <yanfang...@gmail.com> > >>> wrote: > >>> > >> > >>>> > >>> > >> > >>>>> Overall, I agree to couple with Kafka more tightly. > Because > >>> > Samza > >>> > >> de > >>> > >> > >>>>> facto is based on Kafka, and it should leverage what Kafka > >>> has. > >>> > At > >>> > >> > the > >>> > >> > >>>>> same time, Kafka does not need to reinvent what Samza > already > >>> > >> has. I > >>> > >> > >>>>> also like the idea of separating the ingestion and > >>> > transformation. > >>> > >> > >>>>> > >>> > >> > >>>>> But it is a little difficult for me to image how the Samza > >>> will > >>> > >> look > >>> > >> > >>>> like. > >>> > >> > >>>>> And I feel Chris and Jay have a little difference in > terms of > >>> > how > >>> > >> > >>>>> Samza should look like. > >>> > >> > >>>>> > >>> > >> > >>>>> *** Will it look like what Jay's code shows (A client of > >>> Kakfa) > >>> > ? > >>> > >> And > >>> > >> > >>>>> user's application code calls this client? > >>> > >> > >>>>> > >>> > >> > >>>>> 1. If we make Samza be a library of Kafka (like what the > code > >>> > >> shows), > >>> > >> > >>>>> how do we implement auto-balance and fault-tolerance? Are > they > >>> > >> taken > >>> > >> > >>>>> care by the Kafka broker or other mechanism, such as > "Samza > >>> > >> worker" > >>> > >> > >>>>> (just make up the name) ? > >>> > >> > >>>>> > >>> > >> > >>>>> 2. What about other features, such as auto-scaling, shared > >>> > state, > >>> > >> > >>>>> monitoring? > >>> > >> > >>>>> > >>> > >> > >>>>> > >>> > >> > >>>>> *** If we have Samza standalone, (is this what Chris > >>> suggests?) > >>> > >> > >>>>> > >>> > >> > >>>>> 1. we still need to ingest data from Kakfa and produce to > it. > >>> > >> Then it > >>> > >> > >>>>> becomes the same as what Samza looks like now, except it > does > >>> > not > >>> > >> > rely > >>> > >> > >>>>> on Yarn anymore. > >>> > >> > >>>>> > >>> > >> > >>>>> 2. if it is standalone, how can it leverage Kafka's > metrics, > >>> > logs, > >>> > >> > >>>>> etc? Use Kafka code as the dependency? > >>> > >> > >>>>> > >>> > >> > >>>>> > >>> > >> > >>>>> Thanks, > >>> > >> > >>>>> > >>> > >> > >>>>> Fang, Yan > >>> > >> > >>>>> yanfang...@gmail.com > >>> > >> > >>>>> > >>> > >> > >>>>> On Wed, Jul 1, 2015 at 5:46 PM, Guozhang Wang < > >>> > wangg...@gmail.com > >>> > >> > > >>> > >> > >>>> wrote: > >>> > >> > >>>>> > >>> > >> > >>>>>> Read through the code example and it looks good to me. A > few > >>> > >> > >>>>>> thoughts regarding deployment: > >>> > >> > >>>>>> > >>> > >> > >>>>>> Today Samza deploys as executable runnable like: > >>> > >> > >>>>>> > >>> > >> > >>>>>> deploy/samza/bin/run-job.sh --config-factory=... > >>> > >> > >>>> --config-path=file://... > >>> > >> > >>>>>> > >>> > >> > >>>>>> And this proposal advocate for deploying Samza more as > >>> embedded > >>> > >> > >>>>>> libraries in user application code (ignoring the > terminology > >>> > >> since > >>> > >> > >>>>>> it is not the > >>> > >> > >>>>> same > >>> > >> > >>>>>> as the prototype code): > >>> > >> > >>>>>> > >>> > >> > >>>>>> StreamTask task = new MyStreamTask(configs); Thread > thread = > >>> > new > >>> > >> > >>>>>> Thread(task); thread.start(); > >>> > >> > >>>>>> > >>> > >> > >>>>>> I think both of these deployment modes are important for > >>> > >> different > >>> > >> > >>>>>> types > >>> > >> > >>>>> of > >>> > >> > >>>>>> users. That said, I think making Samza purely standalone > is > >>> > still > >>> > >> > >>>>>> sufficient for either runnable or library modes. > >>> > >> > >>>>>> > >>> > >> > >>>>>> Guozhang > >>> > >> > >>>>>> > >>> > >> > >>>>>> On Tue, Jun 30, 2015 at 11:33 PM, Jay Kreps < > >>> j...@confluent.io> > >>> > >> > wrote: > >>> > >> > >>>>>> > >>> > >> > >>>>>>> Looks like gmail mangled the code example, it was > supposed > >>> to > >>> > >> look > >>> > >> > >>>>>>> like > >>> > >> > >>>>>>> this: > >>> > >> > >>>>>>> > >>> > >> > >>>>>>> Properties props = new Properties(); > >>> > >> > >>>>>>> props.put("bootstrap.servers", "localhost:4242"); > >>> > >> StreamingConfig > >>> > >> > >>>>>>> config = new StreamingConfig(props); > >>> > >> > >>>>>>> config.subscribe("test-topic-1", "test-topic-2"); > >>> > >> > >>>>>>> config.processor(ExampleStreamProcessor.class); > >>> > >> > >>>>>>> config.serialization(new StringSerializer(), new > >>> > >> > >>>>>>> StringDeserializer()); KafkaStreaming container = new > >>> > >> > >>>>>>> KafkaStreaming(config); container.run(); > >>> > >> > >>>>>>> > >>> > >> > >>>>>>> -Jay > >>> > >> > >>>>>>> > >>> > >> > >>>>>>> On Tue, Jun 30, 2015 at 11:32 PM, Jay Kreps < > >>> j...@confluent.io > >>> > > > >>> > >> > >>>> wrote: > >>> > >> > >>>>>>> > >>> > >> > >>>>>>>> Hey guys, > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> This came out of some conversations Chris and I were > having > >>> > >> > >>>>>>>> around > >>> > >> > >>>>>>> whether > >>> > >> > >>>>>>>> it would make sense to use Samza as a kind of data > >>> ingestion > >>> > >> > >>>>> framework > >>> > >> > >>>>>>> for > >>> > >> > >>>>>>>> Kafka (which ultimately lead to KIP-26 "copycat"). This > >>> kind > >>> > of > >>> > >> > >>>>>> combined > >>> > >> > >>>>>>>> with complaints around config and YARN and the > discussion > >>> > >> around > >>> > >> > >>>>>>>> how > >>> > >> > >>>>> to > >>> > >> > >>>>>>>> best do a standalone mode. > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> So the thought experiment was, given that Samza was > >>> basically > >>> > >> > >>>>>>>> already totally Kafka specific, what if you just > embraced > >>> > that > >>> > >> > >>>>>>>> and turned it > >>> > >> > >>>>>> into > >>> > >> > >>>>>>>> something less like a heavyweight framework and more > like a > >>> > >> > >>>>>>>> third > >>> > >> > >>>>> Kafka > >>> > >> > >>>>>>>> client--a kind of "producing consumer" with state > >>> management > >>> > >> > >>>>>> facilities. > >>> > >> > >>>>>>>> Basically a library. Instead of a complex stream > processing > >>> > >> > >>>>>>>> framework > >>> > >> > >>>>>>> this > >>> > >> > >>>>>>>> would actually be a very simple thing, not much more > >>> > >> complicated > >>> > >> > >>>>>>>> to > >>> > >> > >>>>> use > >>> > >> > >>>>>>> or > >>> > >> > >>>>>>>> operate than a Kafka consumer. As Chris said we thought > >>> about > >>> > >> it > >>> > >> > >>>>>>>> a > >>> > >> > >>>>> lot > >>> > >> > >>>>>> of > >>> > >> > >>>>>>>> what Samza (and the other stream processing systems > were > >>> > doing) > >>> > >> > >>>>> seemed > >>> > >> > >>>>>>> like > >>> > >> > >>>>>>>> kind of a hangover from MapReduce. > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> Of course you need to ingest/output data to and from > the > >>> > stream > >>> > >> > >>>>>>>> processing. But when we actually looked into how that > would > >>> > >> > >>>>>>>> work, > >>> > >> > >>>>> Samza > >>> > >> > >>>>>>>> isn't really an ideal data ingestion framework for a > bunch > >>> of > >>> > >> > >>>>> reasons. > >>> > >> > >>>>>> To > >>> > >> > >>>>>>>> really do that right you need a pretty different > internal > >>> > data > >>> > >> > >>>>>>>> model > >>> > >> > >>>>>> and > >>> > >> > >>>>>>>> set of apis. So what if you split them and had an api > for > >>> > Kafka > >>> > >> > >>>>>>>> ingress/egress (copycat AKA KIP-26) and a separate api > for > >>> > >> Kafka > >>> > >> > >>>>>>>> transformation (Samza). > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> This would also allow really embracing the same > terminology > >>> > and > >>> > >> > >>>>>>>> conventions. One complaint about the current state is > that > >>> > the > >>> > >> > >>>>>>>> two > >>> > >> > >>>>>>> systems > >>> > >> > >>>>>>>> kind of feel bolted on. Terminology like "stream" vs > >>> "topic" > >>> > >> and > >>> > >> > >>>>>>> different > >>> > >> > >>>>>>>> config and monitoring systems means you kind of have to > >>> learn > >>> > >> > >>>>>>>> Kafka's > >>> > >> > >>>>>>> way, > >>> > >> > >>>>>>>> then learn Samza's slightly different way, then kind of > >>> > >> > >>>>>>>> understand > >>> > >> > >>>>> how > >>> > >> > >>>>>>> they > >>> > >> > >>>>>>>> map to each other, which having walked a few people > through > >>> > >> this > >>> > >> > >>>>>>>> is surprisingly tricky for folks to get. > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> Since I have been spending a lot of time on airplanes I > >>> > hacked > >>> > >> > >>>>>>>> up an ernest but still somewhat incomplete prototype of > >>> what > >>> > >> > >>>>>>>> this would > >>> > >> > >>>>> look > >>> > >> > >>>>>>>> like. This is just unceremoniously dumped into Kafka > as it > >>> > >> > >>>>>>>> required a > >>> > >> > >>>>>> few > >>> > >> > >>>>>>>> changes to the new consumer. Here is the code: > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>> > >>> > >> > >>>>>> > >>> > >> > >>>>> > >>> > >> > > >>> > > https://github.com/jkreps/kafka/tree/streams/clients/src/main/java/org > >>> > >> > >>>>> /apache/kafka/clients/streaming > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> For the purpose of the prototype I just liberally > renamed > >>> > >> > >>>>>>>> everything > >>> > >> > >>>>> to > >>> > >> > >>>>>>>> try to align it with Kafka with no regard for > >>> compatibility. > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> To use this would be something like this: > >>> > >> > >>>>>>>> Properties props = new Properties(); > >>> > >> > >>>>>>>> props.put("bootstrap.servers", "localhost:4242"); > >>> > >> > >>>>>>>> StreamingConfig config = new > >>> > >> > >>>>> StreamingConfig(props); > >>> > >> > >>>>>>> config.subscribe("test-topic-1", > >>> > >> > >>>>>>>> "test-topic-2"); > >>> > >> config.processor(ExampleStreamProcessor.class); > >>> > >> > >>>>>>> config.serialization(new > >>> > >> > >>>>>>>> StringSerializer(), new StringDeserializer()); > >>> KafkaStreaming > >>> > >> > >>>>>> container = > >>> > >> > >>>>>>>> new KafkaStreaming(config); container.run(); > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> KafkaStreaming is basically the SamzaContainer; > >>> > StreamProcessor > >>> > >> > >>>>>>>> is basically StreamTask. > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> So rather than putting all the class names in a file > and > >>> then > >>> > >> > >>>>>>>> having > >>> > >> > >>>>>> the > >>> > >> > >>>>>>>> job assembled by reflection, you just instantiate the > >>> > container > >>> > >> > >>>>>>>> programmatically. Work is balanced over however many > >>> > instances > >>> > >> > >>>>>>>> of > >>> > >> > >>>>> this > >>> > >> > >>>>>>> are > >>> > >> > >>>>>>>> alive at any time (i.e. if an instance dies, new tasks > are > >>> > >> added > >>> > >> > >>>>>>>> to > >>> > >> > >>>>> the > >>> > >> > >>>>>>>> existing containers without shutting them down). > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> We would provide some glue for running this stuff in > YARN > >>> via > >>> > >> > >>>>>>>> Slider, Mesos via Marathon, and AWS using some of their > >>> tools > >>> > >> > >>>>>>>> but from the > >>> > >> > >>>>>> point > >>> > >> > >>>>>>> of > >>> > >> > >>>>>>>> view of these frameworks these stream processing jobs > are > >>> > just > >>> > >> > >>>>>> stateless > >>> > >> > >>>>>>>> services that can come and go and expand and contract > at > >>> > will. > >>> > >> > >>>>>>>> There > >>> > >> > >>>>> is > >>> > >> > >>>>>>> no > >>> > >> > >>>>>>>> more custom scheduler. > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> Here are some relevant details: > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> 1. It is only ~1300 lines of code, it would get > larger if > >>> we > >>> > >> > >>>>>>>> productionized but not vastly larger. We really do > get a > >>> ton > >>> > >> > >>>>>>>> of > >>> > >> > >>>>>>> leverage > >>> > >> > >>>>>>>> out of Kafka. > >>> > >> > >>>>>>>> 2. Partition management is fully delegated to the new > >>> > >> consumer. > >>> > >> > >>>>> This > >>> > >> > >>>>>>>> is nice since now any partition management strategy > >>> > available > >>> > >> > >>>>>>>> to > >>> > >> > >>>>>> Kafka > >>> > >> > >>>>>>>> consumer is also available to Samza (and vice versa) > and > >>> > with > >>> > >> > >>>>>>>> the > >>> > >> > >>>>>>> exact > >>> > >> > >>>>>>>> same configs. > >>> > >> > >>>>>>>> 3. It supports state as well as state reuse > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> Anyhow take a look, hopefully it is thought provoking. > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> -Jay > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> On Tue, Jun 30, 2015 at 6:55 PM, Chris Riccomini < > >>> > >> > >>>>>> criccom...@apache.org> > >>> > >> > >>>>>>>> wrote: > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>>> Hey all, > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> I have had some discussions with Samza engineers at > >>> LinkedIn > >>> > >> > >>>>>>>>> and > >>> > >> > >>>>>>> Confluent > >>> > >> > >>>>>>>>> and we came up with a few observations and would like > to > >>> > >> > >>>>>>>>> propose > >>> > >> > >>>>> some > >>> > >> > >>>>>>>>> changes. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> We've observed some things that I want to call out > about > >>> > >> > >>>>>>>>> Samza's > >>> > >> > >>>>>> design, > >>> > >> > >>>>>>>>> and I'd like to propose some changes. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> * Samza is dependent upon a dynamic deployment system. > >>> > >> > >>>>>>>>> * Samza is too pluggable. > >>> > >> > >>>>>>>>> * Samza's SystemConsumer/SystemProducer and Kafka's > >>> consumer > >>> > >> > >>>>>>>>> APIs > >>> > >> > >>>>> are > >>> > >> > >>>>>>>>> trying to solve a lot of the same problems. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> All three of these issues are related, but I'll > address > >>> them > >>> > >> in > >>> > >> > >>>>> order. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Deployment > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Samza strongly depends on the use of a dynamic > deployment > >>> > >> > >>>>>>>>> scheduler > >>> > >> > >>>>>> such > >>> > >> > >>>>>>>>> as > >>> > >> > >>>>>>>>> YARN, Mesos, etc. When we initially built Samza, we > bet > >>> that > >>> > >> > >>>>>>>>> there > >>> > >> > >>>>>> would > >>> > >> > >>>>>>>>> be > >>> > >> > >>>>>>>>> one or two winners in this area, and we could support > >>> them, > >>> > >> and > >>> > >> > >>>>>>>>> the > >>> > >> > >>>>>> rest > >>> > >> > >>>>>>>>> would go away. In reality, there are many variations. > >>> > >> > >>>>>>>>> Furthermore, > >>> > >> > >>>>>> many > >>> > >> > >>>>>>>>> people still prefer to just start their processors > like > >>> > normal > >>> > >> > >>>>>>>>> Java processes, and use traditional deployment scripts > >>> such > >>> > as > >>> > >> > >>>>>>>>> Fabric, > >>> > >> > >>>>>> Chef, > >>> > >> > >>>>>>>>> Ansible, etc. Forcing a deployment system on users > makes > >>> the > >>> > >> > >>>>>>>>> Samza start-up process really painful for first time > >>> users. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Dynamic deployment as a requirement was also a bit of > a > >>> > >> > >>>>>>>>> mis-fire > >>> > >> > >>>>>> because > >>> > >> > >>>>>>>>> of > >>> > >> > >>>>>>>>> a fundamental misunderstanding between the nature of > batch > >>> > >> jobs > >>> > >> > >>>>>>>>> and > >>> > >> > >>>>>>> stream > >>> > >> > >>>>>>>>> processing jobs. Early on, we made conscious effort to > >>> favor > >>> > >> > >>>>>>>>> the > >>> > >> > >>>>>> Hadoop > >>> > >> > >>>>>>>>> (Map/Reduce) way of doing things, since it worked and > was > >>> > well > >>> > >> > >>>>>>> understood. > >>> > >> > >>>>>>>>> One thing that we missed was that batch jobs have a > >>> definite > >>> > >> > >>>>>> beginning, > >>> > >> > >>>>>>>>> and > >>> > >> > >>>>>>>>> end, and stream processing jobs don't (usually). This > >>> leads > >>> > to > >>> > >> > >>>>>>>>> a > >>> > >> > >>>>> much > >>> > >> > >>>>>>>>> simpler scheduling problem for stream processors. You > >>> > >> basically > >>> > >> > >>>>>>>>> just > >>> > >> > >>>>>>> need > >>> > >> > >>>>>>>>> to find a place to start the processor, and start it. > The > >>> > way > >>> > >> > >>>>>>>>> we run grids, at LinkedIn, there's no concept of a > cluster > >>> > >> > >>>>>>>>> being "full". We always > >>> > >> > >>>>>> add > >>> > >> > >>>>>>>>> more machines. The problem with coupling Samza with a > >>> > >> scheduler > >>> > >> > >>>>>>>>> is > >>> > >> > >>>>>> that > >>> > >> > >>>>>>>>> Samza (as a framework) now has to handle deployment. > This > >>> > >> pulls > >>> > >> > >>>>>>>>> in a > >>> > >> > >>>>>>> bunch > >>> > >> > >>>>>>>>> of things such as configuration distribution (config > >>> > stream), > >>> > >> > >>>>>>>>> shell > >>> > >> > >>>>>>> scrips > >>> > >> > >>>>>>>>> (bin/run-job.sh, JobRunner), packaging (all the .tgz > >>> stuff), > >>> > >> etc. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Another reason for requiring dynamic deployment was to > >>> > support > >>> > >> > >>>>>>>>> data locality. If you want to have locality, you need > to > >>> put > >>> > >> > >>>>>>>>> your > >>> > >> > >>>>>> processors > >>> > >> > >>>>>>>>> close to the data they're processing. Upon further > >>> > >> > >>>>>>>>> investigation, > >>> > >> > >>>>>>> though, > >>> > >> > >>>>>>>>> this feature is not that beneficial. There is some > good > >>> > >> > >>>>>>>>> discussion > >>> > >> > >>>>>> about > >>> > >> > >>>>>>>>> some problems with it on SAMZA-335. Again, we took the > >>> > >> > >>>>>>>>> Map/Reduce > >>> > >> > >>>>>> path, > >>> > >> > >>>>>>>>> but > >>> > >> > >>>>>>>>> there are some fundamental differences between HDFS > and > >>> > Kafka. > >>> > >> > >>>>>>>>> HDFS > >>> > >> > >>>>>> has > >>> > >> > >>>>>>>>> blocks, while Kafka has partitions. This leads to less > >>> > >> > >>>>>>>>> optimization potential with stream processors on top > of > >>> > Kafka. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> This feature is also used as a crutch. Samza doesn't > have > >>> > any > >>> > >> > >>>>>>>>> built > >>> > >> > >>>>> in > >>> > >> > >>>>>>>>> fault-tolerance logic. Instead, it depends on the > dynamic > >>> > >> > >>>>>>>>> deployment scheduling system to handle restarts when a > >>> > >> > >>>>>>>>> processor dies. This has > >>> > >> > >>>>>>> made > >>> > >> > >>>>>>>>> it very difficult to write a standalone Samza > container > >>> > >> > >>>> (SAMZA-516). > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Pluggability > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> In some cases pluggability is good, but I think that > we've > >>> > >> gone > >>> > >> > >>>>>>>>> too > >>> > >> > >>>>>> far > >>> > >> > >>>>>>>>> with it. Currently, Samza has: > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> * Pluggable config. > >>> > >> > >>>>>>>>> * Pluggable metrics. > >>> > >> > >>>>>>>>> * Pluggable deployment systems. > >>> > >> > >>>>>>>>> * Pluggable streaming systems (SystemConsumer, > >>> > SystemProducer, > >>> > >> > >>>> etc). > >>> > >> > >>>>>>>>> * Pluggable serdes. > >>> > >> > >>>>>>>>> * Pluggable storage engines. > >>> > >> > >>>>>>>>> * Pluggable strategies for just about every component > >>> > >> > >>>>> (MessageChooser, > >>> > >> > >>>>>>>>> SystemStreamPartitionGrouper, ConfigRewriter, etc). > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> There's probably more that I've forgotten, as well. > Some > >>> of > >>> > >> > >>>>>>>>> these > >>> > >> > >>>>> are > >>> > >> > >>>>>>>>> useful, but some have proven not to be. This all > comes at > >>> a > >>> > >> cost: > >>> > >> > >>>>>>>>> complexity. This complexity is making it harder for > our > >>> > users > >>> > >> > >>>>>>>>> to > >>> > >> > >>>>> pick > >>> > >> > >>>>>> up > >>> > >> > >>>>>>>>> and use Samza out of the box. It also makes it > difficult > >>> for > >>> > >> > >>>>>>>>> Samza developers to reason about what the > characteristics > >>> of > >>> > >> > >>>>>>>>> the container (since the characteristics change > depending > >>> on > >>> > >> > >>>>>>>>> which plugins are use). > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> The issues with pluggability are most visible in the > >>> System > >>> > >> APIs. > >>> > >> > >>>>> What > >>> > >> > >>>>>>>>> Samza really requires to be functional is Kafka as its > >>> > >> > >>>>>>>>> transport > >>> > >> > >>>>>> layer. > >>> > >> > >>>>>>>>> But > >>> > >> > >>>>>>>>> we've conflated two unrelated use cases into one API: > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> 1. Get data into/out of Kafka. > >>> > >> > >>>>>>>>> 2. Process the data in Kafka. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> The current System API supports both of these use > cases. > >>> The > >>> > >> > >>>>>>>>> problem > >>> > >> > >>>>>> is, > >>> > >> > >>>>>>>>> we > >>> > >> > >>>>>>>>> actually want different features for each use case. By > >>> > >> papering > >>> > >> > >>>>>>>>> over > >>> > >> > >>>>>>> these > >>> > >> > >>>>>>>>> two use cases, and providing a single API, we've > >>> introduced > >>> > a > >>> > >> > >>>>>>>>> ton of > >>> > >> > >>>>>>> leaky > >>> > >> > >>>>>>>>> abstractions. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> For example, what we'd really like in (2) is to have > >>> > >> > >>>>>>>>> monotonically increasing longs for offsets (like > Kafka). > >>> > This > >>> > >> > >>>>>>>>> would be at odds > >>> > >> > >>>>> with > >>> > >> > >>>>>>> (1), > >>> > >> > >>>>>>>>> though, since different systems have different > >>> > >> > >>>>>>> SCNs/Offsets/UUIDs/vectors. > >>> > >> > >>>>>>>>> There was discussion both on the mailing list and the > SQL > >>> > >> JIRAs > >>> > >> > >>>>> about > >>> > >> > >>>>>>> the > >>> > >> > >>>>>>>>> need for this. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> The same thing holds true for replayability. Kafka > allows > >>> us > >>> > >> to > >>> > >> > >>>>> rewind > >>> > >> > >>>>>>>>> when > >>> > >> > >>>>>>>>> we have a failure. Many other systems don't. In some > >>> cases, > >>> > >> > >>>>>>>>> systems > >>> > >> > >>>>>>> return > >>> > >> > >>>>>>>>> null for their offsets (e.g. WikipediaSystemConsumer) > >>> > because > >>> > >> > >>>>>>>>> they > >>> > >> > >>>>>> have > >>> > >> > >>>>>>> no > >>> > >> > >>>>>>>>> offsets. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Partitioning is another example. Kafka supports > >>> > partitioning, > >>> > >> > >>>>>>>>> but > >>> > >> > >>>>> many > >>> > >> > >>>>>>>>> systems don't. We model this by having a single > partition > >>> > for > >>> > >> > >>>>>>>>> those systems. Still, other systems model partitioning > >>> > >> > >>>> differently (e.g. > >>> > >> > >>>>>>>>> Kinesis). > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> The SystemAdmin interface is also a mess. Creating > streams > >>> > in > >>> > >> a > >>> > >> > >>>>>>>>> system-agnostic way is almost impossible. As is > modeling > >>> > >> > >>>>>>>>> metadata > >>> > >> > >>>>> for > >>> > >> > >>>>>>> the > >>> > >> > >>>>>>>>> system (replication factor, partitions, location, > etc). > >>> The > >>> > >> > >>>>>>>>> list > >>> > >> > >>>>> goes > >>> > >> > >>>>>>> on. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Duplicate work > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> At the time that we began writing Samza, Kafka's > consumer > >>> > and > >>> > >> > >>>>> producer > >>> > >> > >>>>>>>>> APIs > >>> > >> > >>>>>>>>> had a relatively weak feature set. On the > consumer-side, > >>> you > >>> > >> > >>>>>>>>> had two > >>> > >> > >>>>>>>>> options: use the high level consumer, or the simple > >>> > consumer. > >>> > >> > >>>>>>>>> The > >>> > >> > >>>>>>> problem > >>> > >> > >>>>>>>>> with the high-level consumer was that it controlled > your > >>> > >> > >>>>>>>>> offsets, partition assignments, and the order in > which you > >>> > >> > >>>>>>>>> received messages. The > >>> > >> > >>>>> problem > >>> > >> > >>>>>>>>> with > >>> > >> > >>>>>>>>> the simple consumer is that it's not simple. It's > basic. > >>> You > >>> > >> > >>>>>>>>> end up > >>> > >> > >>>>>>> having > >>> > >> > >>>>>>>>> to handle a lot of really low-level stuff that you > >>> > shouldn't. > >>> > >> > >>>>>>>>> We > >>> > >> > >>>>>> spent a > >>> > >> > >>>>>>>>> lot of time to make Samza's KafkaSystemConsumer very > >>> robust. > >>> > >> It > >>> > >> > >>>>>>>>> also allows us to support some cool features: > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> * Per-partition message ordering and prioritization. > >>> > >> > >>>>>>>>> * Tight control over partition assignment to support > >>> joins, > >>> > >> > >>>>>>>>> global > >>> > >> > >>>>>> state > >>> > >> > >>>>>>>>> (if we want to implement it :)), etc. > >>> > >> > >>>>>>>>> * Tight control over offset checkpointing. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> What we didn't realize at the time is that these > features > >>> > >> > >>>>>>>>> should > >>> > >> > >>>>>>> actually > >>> > >> > >>>>>>>>> be in Kafka. A lot of Kafka consumers (not just Samza > >>> stream > >>> > >> > >>>>>> processors) > >>> > >> > >>>>>>>>> end up wanting to do things like joins and partition > >>> > >> > >>>>>>>>> assignment. The > >>> > >> > >>>>>>> Kafka > >>> > >> > >>>>>>>>> community has come to the same conclusion. They're > adding > >>> a > >>> > >> ton > >>> > >> > >>>>>>>>> of upgrades into their new Kafka consumer > implementation. > >>> > To a > >>> > >> > >>>>>>>>> large extent, > >>> > >> > >>>>> it's > >>> > >> > >>>>>>>>> duplicate work to what we've already done in Samza. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> On top of this, Kafka ended up taking a very similar > >>> > approach > >>> > >> > >>>>>>>>> to > >>> > >> > >>>>>> Samza's > >>> > >> > >>>>>>>>> KafkaCheckpointManager implementation for handling > offset > >>> > >> > >>>>>> checkpointing. > >>> > >> > >>>>>>>>> Like Samza, Kafka's new offset management feature > stores > >>> > >> offset > >>> > >> > >>>>>>>>> checkpoints in a topic, and allows you to fetch them > from > >>> > the > >>> > >> > >>>>>>>>> broker. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> A lot of this seems like a waste, since we could have > >>> shared > >>> > >> > >>>>>>>>> the > >>> > >> > >>>>> work > >>> > >> > >>>>>> if > >>> > >> > >>>>>>>>> it > >>> > >> > >>>>>>>>> had been done in Kafka from the get-go. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Vision > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> All of this leads me to a rather radical proposal. > Samza > >>> is > >>> > >> > >>>>> relatively > >>> > >> > >>>>>>>>> stable at this point. I'd venture to say that we're > near a > >>> > 1.0 > >>> > >> > >>>>>> release. > >>> > >> > >>>>>>>>> I'd > >>> > >> > >>>>>>>>> like to propose that we take what we've learned, and > begin > >>> > >> > >>>>>>>>> thinking > >>> > >> > >>>>>>> about > >>> > >> > >>>>>>>>> Samza beyond 1.0. What would we change if we were > starting > >>> > >> from > >>> > >> > >>>>>> scratch? > >>> > >> > >>>>>>>>> My > >>> > >> > >>>>>>>>> proposal is to: > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> 1. Make Samza standalone the *only* way to run Samza > >>> > >> > >>>>>>>>> processors, and eliminate all direct dependences on > YARN, > >>> > >> Mesos, > >>> > >> > >>>> etc. > >>> > >> > >>>>>>>>> 2. Make a definitive call to support only Kafka as the > >>> > stream > >>> > >> > >>>>>> processing > >>> > >> > >>>>>>>>> layer. > >>> > >> > >>>>>>>>> 3. Eliminate Samza's metrics, logging, serialization, > and > >>> > >> > >>>>>>>>> config > >>> > >> > >>>>>>> systems, > >>> > >> > >>>>>>>>> and simply use Kafka's instead. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> This would fix all of the issues that I outlined > above. It > >>> > >> > >>>>>>>>> should > >>> > >> > >>>>> also > >>> > >> > >>>>>>>>> shrink the Samza code base pretty dramatically. > Supporting > >>> > >> only > >>> > >> > >>>>>>>>> a standalone container will allow Samza to be > executed on > >>> > YARN > >>> > >> > >>>>>>>>> (using Slider), Mesos (using Marathon/Aurora), or most > >>> other > >>> > >> > >>>>>>>>> in-house > >>> > >> > >>>>>>> deployment > >>> > >> > >>>>>>>>> systems. This should make life a lot easier for new > users. > >>> > >> > >>>>>>>>> Imagine > >>> > >> > >>>>>>> having > >>> > >> > >>>>>>>>> the hello-samza tutorial without YARN. The drop in > mailing > >>> > >> list > >>> > >> > >>>>>> traffic > >>> > >> > >>>>>>>>> will be pretty dramatic. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Coupling with Kafka seems long overdue to me. The > reality > >>> > is, > >>> > >> > >>>>> everyone > >>> > >> > >>>>>>>>> that > >>> > >> > >>>>>>>>> I'm aware of is using Samza with Kafka. We basically > >>> require > >>> > >> it > >>> > >> > >>>>>> already > >>> > >> > >>>>>>> in > >>> > >> > >>>>>>>>> order for most features to work. Those that are using > >>> other > >>> > >> > >>>>>>>>> systems > >>> > >> > >>>>>> are > >>> > >> > >>>>>>>>> generally using it for ingest into Kafka (1), and then > >>> they > >>> > do > >>> > >> > >>>>>>>>> the processing on top. There is already discussion ( > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>> > >>> > >> > >>>>>> > >>> > >> > >>>>> > >>> > >> > > >>> > > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=58851 > >>> > >> > >>>>> 767 > >>> > >> > >>>>>>>>> ) > >>> > >> > >>>>>>>>> in Kafka to make ingesting into Kafka extremely easy. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Once we make the call to couple with Kafka, we can > >>> leverage > >>> > a > >>> > >> > >>>>>>>>> ton of > >>> > >> > >>>>>>> their > >>> > >> > >>>>>>>>> ecosystem. We no longer have to maintain our own > config, > >>> > >> > >>>>>>>>> metrics, > >>> > >> > >>>>> etc. > >>> > >> > >>>>>>> We > >>> > >> > >>>>>>>>> can all share the same libraries, and make them > better. > >>> This > >>> > >> > >>>>>>>>> will > >>> > >> > >>>>> also > >>> > >> > >>>>>>>>> allow us to share the consumer/producer APIs, and > will let > >>> > us > >>> > >> > >>>>> leverage > >>> > >> > >>>>>>>>> their offset management and partition management, > rather > >>> > than > >>> > >> > >>>>>>>>> having > >>> > >> > >>>>>> our > >>> > >> > >>>>>>>>> own. All of the coordinator stream code would go > away, as > >>> > >> would > >>> > >> > >>>>>>>>> most > >>> > >> > >>>>>> of > >>> > >> > >>>>>>>>> the > >>> > >> > >>>>>>>>> YARN AppMaster code. We'd probably have to push some > >>> > partition > >>> > >> > >>>>>>> management > >>> > >> > >>>>>>>>> features into the Kafka broker, but they're already > moving > >>> > in > >>> > >> > >>>>>>>>> that direction with the new consumer API. The > features we > >>> > have > >>> > >> > >>>>>>>>> for > >>> > >> > >>>>>> partition > >>> > >> > >>>>>>>>> assignment aren't unique to Samza, and seem like they > >>> should > >>> > >> be > >>> > >> > >>>>>>>>> in > >>> > >> > >>>>>> Kafka > >>> > >> > >>>>>>>>> anyway. There will always be some niche usages which > will > >>> > >> > >>>>>>>>> require > >>> > >> > >>>>>> extra > >>> > >> > >>>>>>>>> care and hence full control over partition assignments > >>> much > >>> > >> > >>>>>>>>> like the > >>> > >> > >>>>>>> Kafka > >>> > >> > >>>>>>>>> low level consumer api. These would continue to be > >>> > supported. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> These items will be good for the Samza community. > They'll > >>> > make > >>> > >> > >>>>>>>>> Samza easier to use, and make it easier for > developers to > >>> > add > >>> > >> > >>>>>>>>> new features. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Obviously this is a fairly large (and somewhat > backwards > >>> > >> > >>>>> incompatible > >>> > >> > >>>>>>>>> change). If we choose to go this route, it's important > >>> that > >>> > we > >>> > >> > >>>>> openly > >>> > >> > >>>>>>>>> communicate how we're going to provide a migration > path > >>> from > >>> > >> > >>>>>>>>> the > >>> > >> > >>>>>>> existing > >>> > >> > >>>>>>>>> APIs to the new ones (if we make incompatible > changes). I > >>> > >> think > >>> > >> > >>>>>>>>> at a minimum, we'd probably need to provide a wrapper > to > >>> > allow > >>> > >> > >>>>>>>>> existing StreamTask implementations to continue > running on > >>> > the > >>> > >> > >>>> new container. > >>> > >> > >>>>>>> It's > >>> > >> > >>>>>>>>> also important that we openly communicate about > timing, > >>> and > >>> > >> > >>>>>>>>> stages > >>> > >> > >>>>> of > >>> > >> > >>>>>>> the > >>> > >> > >>>>>>>>> migration. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> If you made it this far, I'm sure you have opinions. > :) > >>> > Please > >>> > >> > >>>>>>>>> send > >>> > >> > >>>>>> your > >>> > >> > >>>>>>>>> thoughts and feedback. > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>>> Cheers, > >>> > >> > >>>>>>>>> Chris > >>> > >> > >>>>>>>>> > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>>> > >>> > >> > >>>>>>> > >>> > >> > >>>>>> > >>> > >> > >>>>>> > >>> > >> > >>>>>> > >>> > >> > >>>>>> -- > >>> > >> > >>>>>> -- Guozhang > >>> > >> > >>>>>> > >>> > >> > >>>>> > >>> > >> > >>>> > >>> > >> > >> > >>> > >> > >> > >>> > >> > > >>> > >> > > >>> > >> > > >>> > >> > >>> > > > >>> > > > >>> > > >>> >
