+ 1, me2
On 8/12/16, 9:27 AM, "Amit Sela" <amitsel...@gmail.com> wrote: >+1 as in I'll join ;-) > >On Fri, Aug 12, 2016, 19:14 Eugene Kirpichov <kirpic...@google.com.invalid> >wrote: > >> Sounds good, thanks! >> Then Friday Aug 19th it is, 8am-9am PST, >> https://staging.talkgadget.google.com/hangouts/_/google.com/splittabledofn >> >> On Thu, Aug 11, 2016 at 11:12 PM Jean-Baptiste Onofré <j...@nanthrax.net> >> wrote: >> >> > Hi >> > >> > Unfortunately I will be in Ireland on August 15th. What about Friday >> 19th ? >> > >> > Regards >> > JB >> > >> > >> > >> > On Aug 11, 2016, 23:22, at 23:22, Eugene Kirpichov >> > <kirpic...@google.com.INVALID> wrote: >> > >Hi JB, >> > > >> > >Sounds great, does the suggested time over videoconference work for >> > >you? >> > > >> > >On Thu, Aug 11, 2016 at 11:59 AM Jean-Baptiste Onofré <j...@nanthrax.net> >> > >wrote: >> > > >> > >> Hi Eugene >> > >> >> > >> May we talk together next week ? I like the proposal. I would just >> > >need >> > >> some details for my understanding. >> > >> >> > >> Thanks >> > >> Regards >> > >> JB >> > >> >> > >> >> > >> >> > >> On Aug 11, 2016, 19:46, at 19:46, Eugene Kirpichov >> > >> <kirpic...@google.com.INVALID> wrote: >> > >> >Hi JB, >> > >> > >> > >> >What are your thoughts on this? >> > >> > >> > >> >I'm also thinking of having a virtual meeting to explain more about >> > >> >this >> > >> >proposal if necessary, since I understand it is a lot to digest. >> > >> > >> > >> >How about: Monday Aug 15, 8am-9am Pacific time, over Hangouts? >> > >> >(link: >> > >> > >> > >> >> > > >> > >> https://staging.talkgadget.google.com/hangouts/_/google.com/splittabledofn >> > >> >- >> > >> >I confirmed that it can be joined without being logged into a Google >> > >> >account) >> > >> > >> > >> >Who'd be interested in attending, and does this time/date work for >> > >> >people? >> > >> > >> > >> >On Fri, Aug 5, 2016 at 10:48 AM Eugene Kirpichov >> > ><kirpic...@google.com> >> > >> >wrote: >> > >> > >> > >> >> Hi JB, thanks for reading and for your comments! >> > >> >> >> > >> >> It sounds like you are concerned about continued support for >> > >existing >> > >> >IO's >> > >> >> people have developed, and about backward compatibility? >> > >> >> >> > >> >> We do not need to remove the Source API, and all existing >> > >> >Source-based >> > >> >> connectors will continue to work [though the document proposes at >> > >> >some >> > >> >> point to make Read.from(Source) to translate to a wrapper SDF >> > >under >> > >> >the >> > >> >> hood, to exercise the feature more and to make sure that it is >> > >> >strictly >> > >> >> more powerful - but this is an optional implementation detail]. >> > >> >> >> > >> >> Perhaps the document phrases this too strongly - "replacing the >> > >> >Source >> > >> >> API": a better phrasing would be "introducing a new API so >> > >powerful >> > >> >and >> > >> >> easy-to-use that hopefully people will choose it over the Source >> > >API >> > >> >all >> > >> >> the time, even though they don't have to" :) And we can discuss >> > >> >whether or >> > >> >> not to actually deprecate/remove the Source API at some point down >> > >> >the >> > >> >> road, once it becomes clear whether this is the case or not. >> > >> >> >> > >> >> To give more context: this proposal came out of discussions within >> > >> >the SDK >> > >> >> team over the past ~1.5 years, before the Beam project existed, on >> > >> >how to >> > >> >> make major improvements to the Source API; perhaps it will clarify >> > >> >things >> > >> >> if I give a history of the ideas discussed: >> > >> >> - The first idea was to introduce a Read.from(PCollection<Source>) >> > >> >> transform while keeping the Source API intact - this, given >> > >> >appropriate >> > >> >> implementation, would solve most of the scalability and >> > >composability >> > >> >> issues of IO's. Then most connectors would look like : ParDo<A, >> > >> >Source<B>> >> > >> >> + Read.from(). >> > >> >> - Then we figured that the Source class is an unnecessary >> > >> >abstraction, as >> > >> >> it simply holds data. What if we only had a Reader<S, B> class >> > >where >> > >> >S is >> > >> >> the source type and B the output type? Then connectors would be >> > >> >something >> > >> >> like: ParDo<A, S> + hypothetical Read.using(Reader<S, B>). >> > >> >> - Then somebody remarked that some of the features of Source are >> > >> >useful to >> > >> >> ParDo's as well: e.g. ability to report progress when processing a >> > >> >very >> > >> >> heavy element, or ability to produce very large output in >> > >parallel. >> > >> >> - The two previous bullets were already hinting that the >> > >Read.using() >> > >> >> primitive might not be so special: it just takes S and produces B: >> > >> >isn't >> > >> >> that what a ParDo does, plus some source magic, minus the >> > >convenience >> > >> >of >> > >> >> c.output() vs. the start/advance() state machine? >> > >> >> - At this point it became clear that we should explore unifying >> > >> >sources >> > >> >> and ParDo's, in particular: can we bring the magic of sources to >> > >> >ParDo's >> > >> >> but without the limitations and coding inconveniences? And this is >> > >> >how >> > >> >> SplittableDoFn was born: bringing source magic to a DoFn by >> > >providing >> > >> >a >> > >> >> RangeTracker. >> > >> >> - Once the idea of "splittable DoFn's" was born, it became clear >> > >that >> > >> >it >> > >> >> is strictly more general than sources; at least, in the respect >> > >that >> > >> >> sources have to produce output, while DoFn's don't: an SDF may >> > >very >> > >> >well >> > >> >> produce no output at all, and simply perform a side effect in a >> > >> >> parallel/resumable way. >> > >> >> - Then there were countless hours of discussions on unifying the >> > >> >> bounded/unbounded cases, on the particulars of RangeTracker APIs >> > >> >> reconciling parallelization and checkpointing, what the relation >> > >> >between >> > >> >> SDF and DF should be, etc. They culminated in the current >> > >proposal. >> > >> >The >> > >> >> proposal comes at a time when a couple of key ingredients are >> > >> >(almost) >> > >> >> ready: NewDoFn to make SDF look like a regular DoFn, and the >> > >> >State/Timers >> > >> >> proposal to enable unbounded work per element. >> > >> >> >> > >> >> To put it shortly: >> > >> >> - Yes, we will support existing Source connectors, and will >> > >support >> > >> >> writing new ones, possibly forever. There is no interference with >> > >> >current >> > >> >> users of Source. >> > >> >> - The new API is an attempt to improve the Source API, taken to >> > >its >> > >> >> logical limit where it turns out that users' goals can be >> > >> >accomplished >> > >> >> easier and more generically entirely within ParDo's. >> > >> >> >> > >> >> Let me know what you think, and thanks again! >> > >> >> >> > >> >> On Fri, Aug 5, 2016 at 2:39 AM Jean-Baptiste Onofré >> > ><j...@nanthrax.net> >> > >> >> wrote: >> > >> >> >> > >> >>> Hi Eugene, >> > >> >>> >> > >> >>> Just a question: why is it in DoFn and note an improvement of >> > >Source >> > >> >? >> > >> >>> >> > >> >>> If I understand correctly, it means that we will have to >> > >refactore >> > >> >all >> > >> >>> existing IO: basically, what you propose is to remove all Source >> > >to >> > >> >>> replace with NewDoFn. >> > >> >>> >> > >> >>> I'm concern with this approach, especially in term of timing: >> > >> >clearly, >> > >> >>> the IO is the area where we have to move forward in Beam as it >> > >will >> > >> >>> allow new users to start in their projects. >> > >> >>> So, we started to bring new IOs: Kafka, JMS, Cassandra, MongoDB, >> > >> >JDBC, >> > >> >>> ... and some people started to learn the IO API (Bounded/Unbouded >> > >> >>> source, etc). >> > >> >>> >> > >> >>> I think it would make more sense to enhance the IO API (Source) >> > >> >instead >> > >> >>> of introducing a NewDoFn. >> > >> >>> >> > >> >>> What are your thoughts for IO writer like me ? ;) >> > >> >>> >> > >> >>> Regards >> > >> >>> JB >> > >> >>> >> > >> >>> On 08/04/2016 07:45 PM, Eugene Kirpichov wrote: >> > >> >>> > Hello Beam community, >> > >> >>> > >> > >> >>> > We (myself, Daniel Mills and Robert Bradshaw) would like to >> > >> >propose >> > >> >>> > "Splittable DoFn" - a major generalization of DoFn, which >> > >allows >> > >> >>> processing >> > >> >>> > of a single element to be non-monolithic, i.e. checkpointable >> > >and >> > >> >>> > parallelizable, as well as doing an unbounded amount of work >> > >per >> > >> >>> element. >> > >> >>> > >> > >> >>> > This allows effectively replacing the current >> > >> >Bounded/UnboundedSource >> > >> >>> APIs >> > >> >>> > with DoFn's that are much easier to code, more scalable and >> > >> >composable >> > >> >>> with >> > >> >>> > the rest of the Beam programming model, and enables many use >> > >cases >> > >> >that >> > >> >>> > were previously difficult or impossible, as well as some >> > >> >non-obvious new >> > >> >>> > use cases. >> > >> >>> > >> > >> >>> > This proposal has been mentioned before in JIRA [BEAM-65] and >> > >some >> > >> >Beam >> > >> >>> > meetings, and now the whole thing is written up in a document: >> > >> >>> > >> > >> >>> > https://s.apache.org/splittable-do-fn >> > >> >>> > >> > >> >>> > Here are some things that become possible with Splittable DoFn: >> > >> >>> > - Efficiently read a filepattern matching millions of files >> > >> >>> > - Read a collection of files that are produced by an earlier >> > >step >> > >> >in the >> > >> >>> > pipeline (e.g. easily implement a connector to a storage system >> > >> >that can >> > >> >>> > export itself to files) >> > >> >>> > - Implement a Kafka reader by composing a "list partitions" >> > >DoFn >> > >> >with a >> > >> >>> > DoFn that simply polls a consumer and outputs new records in a >> > >> >while() >> > >> >>> loop >> > >> >>> > - Implement a log tailer by composing a DoFn that incrementally >> > >> >returns >> > >> >>> new >> > >> >>> > files in a directory and a DoFn that tails a file >> > >> >>> > - Implement a parallel "count friends in common" algorithm >> > >(matrix >> > >> >>> > squaring) with good work balancing >> > >> >>> > >> > >> >>> > Here is the meaningful part of a hypothetical Kafka reader >> > >written >> > >> >>> against >> > >> >>> > this API: >> > >> >>> > >> > >> >>> > ProcessContinuation processElement( >> > >> >>> > ProcessContext context, OffsetRangeTracker tracker) >> > >{ >> > >> >>> > try (KafkaConsumer<String, String> consumer = >> > >> >>> > Kafka.subscribe(context.element().topic, >> > >> >>> > context.element().partition)) { >> > >> >>> > consumer.seek(tracker.start()); >> > >> >>> > while (true) { >> > >> >>> > ConsumerRecords<String, String> records = >> > >> >>> consumer.poll(100ms); >> > >> >>> > if (records == null) return done(); >> > >> >>> > for (ConsumerRecord<String, String> record : records) >> > >{ >> > >> >>> > if (!tracker.tryClaim(record.offset())) { >> > >> >>> > return >> > >> >>> resume().withFutureOutputWatermark(record.timestamp()); >> > >> >>> > } >> > >> >>> > context.output(record); >> > >> >>> > } >> > >> >>> > } >> > >> >>> > } >> > >> >>> > } >> > >> >>> > >> > >> >>> > The document describes in detail the motivations behind this >> > >> >feature, >> > >> >>> the >> > >> >>> > basic idea and API, open questions, and outlines an incremental >> > >> >delivery >> > >> >>> > plan. >> > >> >>> > >> > >> >>> > The proposed API builds on the reflection-based new DoFn >> > >> >[new-do-fn] >> > >> >>> and is >> > >> >>> > loosely related to "State and Timers for DoFn" [beam-state]. >> > >> >>> > >> > >> >>> > Please take a look and comment! >> > >> >>> > >> > >> >>> > Thanks. >> > >> >>> > >> > >> >>> > [BEAM-65] https://issues.apache.org/jira/browse/BEAM-65 >> > >> >>> > [new-do-fn] https://s.apache.org/a-new-do-fn >> > >> >>> > [beam-state] https://s.apache.org/beam-state >> > >> >>> > >> > >> >>> >> > >> >>> -- >> > >> >>> Jean-Baptiste Onofré >> > >> >>> jbono...@apache.org >> > >> >>> http://blog.nanthrax.net >> > >> >>> Talend - http://www.talend.com >> > >> >>> >> > >> >> >> > >> >> > >>
