Big thanks to everyone for the ongoing discussions in this thread and on the doc!
The implementation to enable portable dynamic destinations is now underway - GitHub tracker: https://github.com/apache/beam/issues/32365 Best, Ahmed On Wed, Apr 3, 2024 at 1:00 PM Robert Bradshaw via dev <dev@beam.apache.org> wrote: > On Wed, Apr 3, 2024 at 4:15 AM Kenneth Knowles <k...@apache.org> wrote: > >> Let me summarize the most recent proposal on-list to frame my question >> about this last suggestion. It looks like this: >> >> 1. user has an element, call it `data` >> 2. user maps `data` to an arbitrary metadata row, call it `dest` >> 3. we can do things like shuffle on `dest` because it isn't too big >> 4. we map `dest` to a concrete destination (aka URL) to write to by a >> string format that uses fields of `dest` >> >> I believe steps 1-3 are identical is expressivity to non-portable >> DynamicDestinations. So Reuven the question is for step 4: what are the >> mappings from `dest` to URL that cannot be expressed by string formatting >> but need SQL or Lua, etc? That would be a useful guide to consideration of >> those possibilities. >> > > I think any non-trivial mapping can be done in step 2. It may be possible > to come up with a case where something other than string substitution is > needed to be done to make dest small enough to shuffle, but I think that'd > be a really rare corner case, and then it's just an optimization rather > than feature completeness question. > > >> FWIW I think even if we add a mini-language that string formatting has >> better ease of use (can easily be displayed in UI, etc) so it would be the >> first choice, and more advanced stuff is a fallback for rare cases. So they >> are both valuable and I'd be happy to implement the easier-to-use path >> right away while we discuss. >> > > +1. Note that this even lets us share the config "path/table/..." field > that is a static string for non-dynamic destinations. > > In light of the above, let's avoid a complex mini-language. I'd start with > nothing but plugging things in w/o any formatting options. > > >> On Tue, Apr 2, 2024 at 2:59 PM Reuven Lax via dev <dev@beam.apache.org> >> wrote: >> >>> I do suspect that over time we'll find more and more cases we can't >>> express, and will be asked to extend this little templating in more >>> directions. To head that off - could we easily just reuse an existing >>> language (SQL, LUA, something of the form?) instead of creating something >>> new? >>> >>> On Tue, Apr 2, 2024 at 8:55 AM Kenneth Knowles <k...@apache.org> wrote: >>> >>>> I really like this proposal. I think it has narrowed down and solved >>>> the essential problem of not shuffling excess redundant data, and also >>>> provides the vast majority of the functionality that a lambda would, with >>>> significantly better debugability and usability too, since the dynamic >>>> destination pattern string can be in display data, etc. >>>> >>>> Kenn >>>> >>>> On Wed, Mar 27, 2024 at 1:58 PM Robert Bradshaw via dev < >>>> dev@beam.apache.org> wrote: >>>> >>>>> On Wed, Mar 27, 2024 at 10:20 AM Reuven Lax <re...@google.com> wrote: >>>>> >>>>>> Can the prefix still be generated programmatically at graph creation >>>>>> time? >>>>>> >>>>> >>>>> Yes. It's just a property of the transform passed by the user at >>>>> configuration time. >>>>> >>>>> >>>>>> On Wed, Mar 27, 2024 at 9:40 AM Robert Bradshaw <rober...@google.com> >>>>>> wrote: >>>>>> >>>>>>> On Wed, Mar 27, 2024 at 9:12 AM Reuven Lax <re...@google.com> wrote: >>>>>>> >>>>>>>> This does seem like the best compromise, though I think there will >>>>>>>> still end up being performance issues. A common pattern I've seen is >>>>>>>> that >>>>>>>> there is a long common prefix to the dynamic destination followed the >>>>>>>> dynamic component. e.g. the destination might be >>>>>>>> long/common/path/to/destination/files/<per-user-file>. In this case, >>>>>>>> the >>>>>>>> prefix is often much larger than messages themselves and is what gets >>>>>>>> effectively encoded in the lambda. >>>>>>>> >>>>>>> >>>>>>> The idea here is that the destination would be given as a format >>>>>>> string, say, "long/common/path/to/destination/files/{dest_info.user}". >>>>>>> Another way to put this is that we support (only) "lambdas" that are >>>>>>> represented as string substitutions. (The fact that dest_info does not >>>>>>> have >>>>>>> to be part of the record, and can be the output of an arbitrary map if >>>>>>> need >>>>>>> be, makes this restriction not so bad.) >>>>>>> >>>>>>> As well as solving the performance issues, I think this is actually >>>>>>> a pretty convenient and natural way for the user to name their >>>>>>> destination >>>>>>> (for the common usecase, even easier than providing a lambda), and has >>>>>>> the >>>>>>> benefit of being much more transparent than an arbitrary callable as >>>>>>> well >>>>>>> for introspection (for both machine and human that may look at the >>>>>>> resulting pipeline). >>>>>>> >>>>>>> >>>>>>>> I'm not entirely sure how to address this in a portable context. We >>>>>>>> might simply have to accept the extra overhead when going cross >>>>>>>> language. >>>>>>>> >>>>>>>> Reuven >>>>>>>> >>>>>>>> On Wed, Mar 27, 2024 at 8:51 AM Robert Bradshaw via dev < >>>>>>>> dev@beam.apache.org> wrote: >>>>>>>> >>>>>>>>> Thanks for putting this together, it will be a really >>>>>>>>> useful feature to have. >>>>>>>>> >>>>>>>>> I am in favor of the string-pattern approaches. I think we need to >>>>>>>>> support both the {record=..., dest_info=...} and the elide-fields >>>>>>>>> approaches, as the former is nicer when one has a fixed >>>>>>>>> representation for >>>>>>>>> the output record (e.g. a proto or avro schema) and the flattened >>>>>>>>> form for >>>>>>>>> ease of use in more free-form contexts (e.g. when producing records >>>>>>>>> from >>>>>>>>> YAML and SQL). >>>>>>>>> >>>>>>>>> Also left some comments on the doc. >>>>>>>>> >>>>>>>>> >>>>>>>>> On Wed, Mar 27, 2024 at 6:51 AM Ahmed Abualsaud via dev < >>>>>>>>> dev@beam.apache.org> wrote: >>>>>>>>> >>>>>>>>>> Hey all, >>>>>>>>>> >>>>>>>>>> There have been some conversations lately about how best to >>>>>>>>>> enable dynamic destinations in a portable context. Usually, this >>>>>>>>>> comes up >>>>>>>>>> for cross-language transforms and more recently for Beam YAML. >>>>>>>>>> >>>>>>>>>> I've started a short doc outlining some routes we could take. The >>>>>>>>>> purpose is to establish a good standard for supporting dynamic >>>>>>>>>> destinations >>>>>>>>>> with portability, one that can be applied to most use cases and IOs. >>>>>>>>>> Please >>>>>>>>>> take a look and add any thoughts! >>>>>>>>>> >>>>>>>>>> https://s.apache.org/portable-dynamic-destinations >>>>>>>>>> >>>>>>>>>> Best, >>>>>>>>>> Ahmed >>>>>>>>>> >>>>>>>>>
