+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 > > >> >>> > > >> >> > > >> > > >
