hi David, I did a preliminary view and things look to be on the right track there. What do you think about breaking out the protocol changes (and adding appropriate comments) so we can have a vote on that in relatively short order?
- Wes On Wed, Mar 18, 2020 at 9:06 AM David Li <li.david...@gmail.com> wrote: > > Following up here, I've submitted a draft implementation for C++: > https://github.com/apache/arrow/pull/6656 > > The core functionality is there, but there are still holes that I need > to implement. Compared to the draft spec, the client also sends a > FlightDescriptor to begin with, though it's currently not exposed. > This provides consistency with DoGet/DoPut which also send a message > to begin with to describe the stream to the server. > > Andy, I hope this helps clarify whether it meets your needs. > > Best, > David > > On 2/25/20, David Li <li.david...@gmail.com> wrote: > > Hey Andy, > > > > I've been rather busy unfortunately. I had started on an > > implementation in C++ to provide as part of this discussion, but it's > > not complete. I'm hoping to have more done in March. > > > > Best, > > David > > > > On 2/25/20, Andy Grove <andygrov...@gmail.com> wrote: > >> I was wondering if there had been any momentum on this (the BiDirectional > >> RPC design)? > >> > >> I'm interested in this for the use case of Apache Spark sending a stream > >> of > >> data to another process to invoke custom code and then receive a stream > >> back with the transformed data. > >> > >> Thanks, > >> > >> Andy. > >> > >> > >> > >> On Fri, Dec 13, 2019 at 12:12 PM Jacques Nadeau <jacq...@apache.org> > >> wrote: > >> > >>> I support moving forward with the current proposal. > >>> > >>> On Thu, Dec 12, 2019 at 12:20 PM David Li <li.david...@gmail.com> wrote: > >>> > >>> > Just following up here again, any other thoughts? > >>> > > >>> > I think we do have justifications for potentially separate streams in > >>> > a call, but that's more of an orthogonal question - it doesn't need to > >>> > be addressed here. I do agree that it very much complicates things. > >>> > > >>> > Thanks, > >>> > David > >>> > > >>> > On 11/29/19, Wes McKinney <wesmck...@gmail.com> wrote: > >>> > > I would generally agree with this. Note that you have the > >>> > > possibility > >>> > > to use unions-of-structs to send record batches with different > >>> > > schemas > >>> > > in the same stream, though with some added complexity on each side > >>> > > > >>> > > On Thu, Nov 28, 2019 at 10:37 AM Jacques Nadeau <jacq...@apache.org> > >>> > wrote: > >>> > >> > >>> > >> I'd vote for explicitly not supported. We should keep our > >>> > >> primitives > >>> > >> narrow. > >>> > >> > >>> > >> On Wed, Nov 27, 2019, 1:17 PM David Li <li.david...@gmail.com> > >>> > >> wrote: > >>> > >> > >>> > >> > Thanks for the feedback. > >>> > >> > > >>> > >> > I do think if we had explicitly embraced gRPC from the beginning, > >>> > >> > there are a lot of places where things could be made more > >>> > >> > ergonomic, > >>> > >> > including with the metadata fields. But it would also have locked > >>> out > >>> > >> > us of potential future transports. > >>> > >> > > >>> > >> > On another note: I hesitate to put too much into this method, but > >>> > >> > we > >>> > >> > are looking at use cases where potentially, a client may want to > >>> > >> > upload multiple distinct datasets (with differing schemas). (This > >>> is a > >>> > >> > little tentative, and I can get more details...) Right now, each > >>> > >> > logical stream in Flight must have a single, consistent schema; > >>> would > >>> > >> > it make sense to look at ways to relax this, or declare this > >>> > >> > explicitly out of scope (and require multiple calls and > >>> > >> > coordination > >>> > >> > with the deployment topology) in order to accomplish this? > >>> > >> > > >>> > >> > Best, > >>> > >> > David > >>> > >> > > >>> > >> > On 11/27/19, Jacques Nadeau <jacq...@apache.org> wrote: > >>> > >> > > Fair enough. I'm okay with the bytes approach and the proposal > >>> looks > >>> > >> > > good > >>> > >> > > to me. > >>> > >> > > > >>> > >> > > On Fri, Nov 8, 2019 at 11:37 AM David Li > >>> > >> > > <li.david...@gmail.com> > >>> > >> > > wrote: > >>> > >> > > > >>> > >> > >> I've updated the proposal. > >>> > >> > >> > >>> > >> > >> On the subject of Protobuf Any vs bytes, and how to handle > >>> > >> > >> errors/metadata, I still think using bytes is preferable: > >>> > >> > >> - It doesn't require (conditionally) exposing or wrapping > >>> Protobuf > >>> > >> > types, > >>> > >> > >> - We wouldn't be able to practically expose the Protobuf field > >>> > >> > >> to > >>> > >> > >> C++ > >>> > >> > >> users without causing build pains, > >>> > >> > >> - We can't let Python users take advantage of the Protobuf > >>> > >> > >> field > >>> > >> > >> without somehow being compatible with the Protobuf wheels (by > >>> > >> > >> linking > >>> > >> > >> to the same version, and doing magic to turn the C++ Protobufs > >>> into > >>> > >> > >> the Python ones), > >>> > >> > >> - All our other application-defined fields are already bytes. > >>> > >> > >> > >>> > >> > >> Applications that want structure can encode JSON or Protobuf > >>> > >> > >> Any > >>> > >> > >> into > >>> > >> > >> the bytes field themselves, much as you can already do for > >>> Ticket, > >>> > >> > >> commands in FlightDescriptors, and application metadata in > >>> > >> > >> DoGet/DoPut. I don't think this is (much) less efficient than > >>> using > >>> > >> > >> Any directly, since Any itself is a bytes field with a tag, > >>> > >> > >> and > >>> > must > >>> > >> > >> invoke the Protobuf deserializer again to read the actual > >>> message. > >>> > >> > >> > >>> > >> > >> If we decide on using bytes, then I don't think it makes sense > >>> > >> > >> to > >>> > >> > >> define a new message with a oneof either, since it would be > >>> > >> > >> redundant. > >>> > >> > >> > >>> > >> > >> Thanks, > >>> > >> > >> David > >>> > >> > >> > >>> > >> > >> On 11/7/19, David Li <li.david...@gmail.com> wrote: > >>> > >> > >> > I've been extremely backlogged, I will update the proposal > >>> when I > >>> > >> > >> > get > >>> > >> > >> > a chance and reply here when done. > >>> > >> > >> > > >>> > >> > >> > Best, > >>> > >> > >> > David > >>> > >> > >> > > >>> > >> > >> > On 11/7/19, Wes McKinney <wesmck...@gmail.com> wrote: > >>> > >> > >> >> Bumping this discussion since a couple of weeks have > >>> > >> > >> >> passed. > >>> It > >>> > >> > >> >> seems > >>> > >> > >> >> there are still some questions here, could we summarize > >>> > >> > >> >> what > >>> are > >>> > >> > >> >> the > >>> > >> > >> >> alternatives along with any public API implications so we > >>> > >> > >> >> can > >>> > try > >>> > >> > >> >> to > >>> > >> > >> >> render a decision? > >>> > >> > >> >> > >>> > >> > >> >> On Sat, Oct 26, 2019 at 7:19 PM David Li < > >>> li.david...@gmail.com > >>> > > > >>> > >> > >> >> wrote: > >>> > >> > >> >>> > >>> > >> > >> >>> Hi Wes, > >>> > >> > >> >>> > >>> > >> > >> >>> Responses inline: > >>> > >> > >> >>> > >>> > >> > >> >>> On Sat, Oct 26, 2019, 13:46 Wes McKinney < > >>> wesmck...@gmail.com> > >>> > >> > wrote: > >>> > >> > >> >>> > >>> > >> > >> >>> > On Mon, Oct 21, 2019 at 7:40 PM David Li > >>> > >> > >> >>> > <li.david...@gmail.com> > >>> > >> > >> >>> > wrote: > >>> > >> > >> >>> > > > >>> > >> > >> >>> > > The question is whether to repurpose the existing > >>> > FlightData > >>> > >> > >> >>> > > structure, and allow for the metadata field to be > >>> > >> > >> >>> > > filled > >>> in > >>> > >> > >> >>> > > and > >>> > >> > >> data > >>> > >> > >> >>> > > fields to be blank (as a control message), or to wrap > >>> > >> > >> >>> > > the > >>> > >> > >> FlightData > >>> > >> > >> >>> > > structure in another structure that explicitly > >>> > distinguishes > >>> > >> > >> between > >>> > >> > >> >>> > > control and data messages. > >>> > >> > >> >>> > > >>> > >> > >> >>> > I'm not super against having metadata-only FlightData > >>> > >> > >> >>> > with > >>> > >> > >> >>> > empty > >>> > >> > >> body. > >>> > >> > >> >>> > One question to consider is what changes (if any) would > >>> need > >>> > to > >>> > >> > >> >>> > be > >>> > >> > >> >>> > made to public APIs in either scenario. > >>> > >> > >> >>> > > >>> > >> > >> >>> > >>> > >> > >> >>> We could leave DoGet/DoPut as-is for now, and allow empty > >>> data > >>> > >> > >> >>> messages > >>> > >> > >> >>> in > >>> > >> > >> >>> the future. This would be a breaking change, but wouldn't > >>> > change > >>> > >> > >> >>> the > >>> > >> > >> >>> wire > >>> > >> > >> >>> format. I think the APIs could be changed backwards > >>> compatibly, > >>> > >> > >> >>> though. > >>> > >> > >> >>> > >>> > >> > >> >>> > >>> > >> > >> >>> > >>> > >> > >> >>> > > The other question is how to handle the metadata > >>> > >> > >> >>> > > fields. > >>> So > >>> > >> > >> >>> > > far, > >>> > >> > >> >>> > > we've > >>> > >> > >> >>> > > used bytestring fields for application-defined data. > >>> > >> > >> >>> > > This > >>> > is > >>> > >> > >> >>> > > workable > >>> > >> > >> >>> > > if you want to use Protobuf to define the contents of > >>> those > >>> > >> > >> >>> > > fields, > >>> > >> > >> >>> > > but requires you to pack/unpack your Protobuf > >>> > >> > >> >>> > > into/from > >>> the > >>> > >> > >> >>> > > bytestring > >>> > >> > >> >>> > > field. If we instead used the Protobuf Any field, a > >>> > >> > >> >>> > > dynamically > >>> > >> > >> >>> > > typed > >>> > >> > >> >>> > > field, this would be more convenient, but then we'd be > >>> > >> > >> >>> > > exposing > >>> > >> > >> >>> > > Protobuf types. We could alternatively use a > >>> > >> > >> >>> > > combination > >>> of > >>> > >> > >> >>> > > a > >>> > >> > >> >>> > > type > >>> > >> > >> >>> > > field and a bytestring field, mimicking what the > >>> > >> > >> >>> > > Protobuf > >>> > >> > >> >>> > > Any > >>> > >> > >> >>> > > type > >>> > >> > >> >>> > > looks like on the wire. I'm not sure this is actually > >>> > cleaner > >>> > >> > >> >>> > > in > >>> > >> > >> any > >>> > >> > >> >>> > > of the language APIs, though. > >>> > >> > >> >>> > > >>> > >> > >> >>> > Leaving the deserialization of the app metadata to the > >>> > >> > >> >>> > particular > >>> > >> > >> >>> > Flight implementation seems on first principles like the > >>> most > >>> > >> > >> flexible > >>> > >> > >> >>> > thing, if Any is used, does that mean the metadata > >>> > >> > >> >>> > _must_ > >>> be > >>> > a > >>> > >> > >> >>> > protobuf? > >>> > >> > >> >>> > > >>> > >> > >> >>> > >>> > >> > >> >>> > >>> > >> > >> >>> If Any is used, we could still expose a bytes-based API, > >>> > >> > >> >>> but > >>> it > >>> > >> > would > >>> > >> > >> >>> have > >>> > >> > >> >>> some more wrapping. (We could put a ByteString in Any.) > >>> > >> > >> >>> Then > >>> > the > >>> > >> > >> >>> question > >>> > >> > >> >>> would just be how to expose this (would be easier in Java, > >>> > harder > >>> > >> > >> >>> in > >>> > >> > >> >>> C++). > >>> > >> > >> >>> > >>> > >> > >> >>> > >>> > >> > >> >>> > >>> > >> > >> >>> > > David > >>> > >> > >> >>> > > > >>> > >> > >> >>> > > On 10/21/19, Antoine Pitrou <anto...@python.org> > >>> > >> > >> >>> > > wrote: > >>> > >> > >> >>> > > > > >>> > >> > >> >>> > > > Can one of you explain what is being proposed in > >>> > >> > >> >>> > > > non-protobuf > >>> > >> > >> >>> > > > terms? > >>> > >> > >> >>> > > > Knowledge of protobuf shouldn't be required to use > >>> > Flight. > >>> > >> > >> >>> > > > > >>> > >> > >> >>> > > > Regards > >>> > >> > >> >>> > > > > >>> > >> > >> >>> > > > Antoine. > >>> > >> > >> >>> > > > > >>> > >> > >> >>> > > > > >>> > >> > >> >>> > > > Le 21/10/2019 à 15:46, David Li a écrit : > >>> > >> > >> >>> > > >> Oneof doesn't actually change the wire encoding; it > >>> > would > >>> > >> > just > >>> > >> > >> be > >>> > >> > >> >>> > > >> application-level logic. (The official guide > >>> > >> > >> >>> > > >> doesn't > >>> > even > >>> > >> > >> mention > >>> > >> > >> >>> > > >> it > >>> > >> > >> >>> > > >> in the encoding docs; I found > >>> > >> > >> >>> > > >> > >>> > >> > >> >>> > > >>> > >> > >> > >>> > >> > > >>> > > >>> https://stackoverflow.com/questions/52226409/how-protobuf-encodes-oneof-message-construct > >>> > >> > >> >>> > > >> as well.) > >>> > >> > >> >>> > > >> > >>> > >> > >> >>> > > >> If I follow you, Jacques, then you are proposing > >>> > >> > >> >>> > > >> essentially > >>> > >> > >> >>> > > >> inlining > >>> > >> > >> >>> > > >> the definition of Any, e.g. > >>> > >> > >> >>> > > >> > >>> > >> > >> >>> > > >> message FlightMessage { > >>> > >> > >> >>> > > >> oneof message { > >>> > >> > >> >>> > > >> FlightData data = 1; > >>> > >> > >> >>> > > >> FlightAny metadata = 2; > >>> > >> > >> >>> > > >> } > >>> > >> > >> >>> > > >> } > >>> > >> > >> >>> > > >> > >>> > >> > >> >>> > > >> message FlightAny { > >>> > >> > >> >>> > > >> string type = 1; > >>> > >> > >> >>> > > >> bytes data = 2; > >>> > >> > >> >>> > > >> } > >>> > >> > >> >>> > > >> > >>> > >> > >> >>> > > >> Is this correct? > >>> > >> > >> >>> > > >> > >>> > >> > >> >>> > > >> It might be nice to consider the wrapper message > >>> > >> > >> >>> > > >> for > >>> > >> > >> >>> > > >> DoGet/DoPut > >>> > >> > >> >>> > > >> as > >>> > >> > >> >>> > > >> well, but at that point, I'd rather we be > >>> > >> > >> >>> > > >> consistent > >>> > with > >>> > >> > >> >>> > > >> all > >>> > >> > >> >>> > > >> of > >>> > >> > >> >>> > > >> them, > >>> > >> > >> >>> > > >> rather than have one of the three methods do its > >>> > >> > >> >>> > > >> own > >>> > >> > >> >>> > > >> thing. > >>> > >> > >> >>> > > >> > >>> > >> > >> >>> > > >> Thanks, > >>> > >> > >> >>> > > >> David > >>> > >> > >> >>> > > >> > >>> > >> > >> >>> > > >> On 10/20/19, Jacques Nadeau <jacq...@apache.org> > >>> wrote: > >>> > >> > >> >>> > > >>> I think we could probably expose the oneof > >>> > >> > >> >>> > > >>> behavior > >>> > >> > >> >>> > > >>> without > >>> > >> > >> >>> > > >>> exposing > >>> > >> > >> >>> > the > >>> > >> > >> >>> > > >>> protobuf functions. On the any... hmm. I guess we > >>> could > >>> > >> > >> >>> > > >>> expose > >>> > >> > >> >>> > > >>> as > >>> > >> > >> >>> > > >>> two > >>> > >> > >> >>> > > >>> fields: type and data. Then users could use it for > >>> > >> > >> >>> > > >>> whatever > >>> > >> > >> >>> > > >>> but > >>> > >> > >> >>> > > >>> if > >>> > >> > >> >>> > > >>> people > >>> > >> > >> >>> > > >>> wanted to treat it as any, it would work. > >>> > >> > >> >>> > > >>> (Basically > >>> a > >>> > >> > >> >>> > > >>> user > >>> > >> > >> >>> > > >>> could > >>> > >> > >> >>> > > >>> use > >>> > >> > >> >>> > > >>> any > >>> > >> > >> >>> > > >>> with it easily but they could also use any other > >>> > >> > >> >>> > > >>> mechanism). > >>> > >> > >> >>> > > >>> At > >>> > >> > >> >>> > least in > >>> > >> > >> >>> > > >>> java, the any concepts are pretty simple/diy. Are > >>> other > >>> > >> > >> language > >>> > >> > >> >>> > > >>> bindings > >>> > >> > >> >>> > > >>> less diy? > >>> > >> > >> >>> > > >>> > >>> > >> > >> >>> > > >>> I'm *not* hardcore against the empty FlightData + > >>> > >> > >> >>> > > >>> metadata > >>> > >> > >> >>> > > >>> but > >>> > >> > >> >>> > > >>> it > >>> > >> > >> >>> > just > >>> > >> > >> >>> > > >>> seemed a bit janky. > >>> > >> > >> >>> > > >>> > >>> > >> > >> >>> > > >>> Thinking about the control message/wrapper object > >>> > thing, > >>> > >> > >> >>> > > >>> I > >>> > >> > >> >>> > > >>> wonder > >>> > >> > >> >>> > > >>> if > >>> > >> > >> >>> > we > >>> > >> > >> >>> > > >>> should redefine DoPut and DoGet to have the same > >>> > property > >>> > >> > >> >>> > > >>> if > >>> > >> > >> >>> > > >>> we > >>> > >> > >> >>> > think it > >>> > >> > >> >>> > > >>> is > >>> > >> > >> >>> > > >>> a good idea... > >>> > >> > >> >>> > > >>> > >>> > >> > >> >>> > > >>> On Wed, Oct 16, 2019 at 5:13 PM David Li < > >>> > >> > >> li.david...@gmail.com> > >>> > >> > >> >>> > wrote: > >>> > >> > >> >>> > > >>> > >>> > >> > >> >>> > > >>>> I was definitely considering having control > >>> > >> > >> >>> > > >>>> messages > >>> > >> > without > >>> > >> > >> >>> > > >>>> data, > >>> > >> > >> >>> > and > >>> > >> > >> >>> > > >>>> I thought that could be encoded by a FlightData > >>> > >> > >> >>> > > >>>> with > >>> > >> > >> >>> > > >>>> only > >>> > >> > >> >>> > app_metadata > >>> > >> > >> >>> > > >>>> set. I think I understand your position now: > >>> > FlightData > >>> > >> > >> >>> > > >>>> should > >>> > >> > >> >>> > always > >>> > >> > >> >>> > > >>>> carry (some) data (with optional metadata)? > >>> > >> > >> >>> > > >>>> > >>> > >> > >> >>> > > >>>> That makes sense to me, and is consistent with > >>> > >> > >> >>> > > >>>> the > >>> > >> > >> >>> > > >>>> documentation > >>> > >> > >> >>> > > >>>> on > >>> > >> > >> >>> > > >>>> FlightData in the Protobuf file. I was worried > >>> > >> > >> >>> > > >>>> about > >>> > >> > >> >>> > > >>>> having > >>> > >> > >> >>> > > >>>> a > >>> > >> > >> >>> > > >>>> redundant metadata field, but oneof prevents that > >>> from > >>> > >> > >> >>> > > >>>> happening, > >>> > >> > >> >>> > and > >>> > >> > >> >>> > > >>>> overall having a clear separation between data > >>> > >> > >> >>> > > >>>> and > >>> > >> > >> >>> > > >>>> control > >>> > >> > >> >>> > > >>>> messages > >>> > >> > >> >>> > is > >>> > >> > >> >>> > > >>>> cleaner. > >>> > >> > >> >>> > > >>>> > >>> > >> > >> >>> > > >>>> As for using Protobuf's Any: so far, we've > >>> > >> > >> >>> > > >>>> refrained > >>> > >> > >> >>> > > >>>> from > >>> > >> > >> >>> > > >>>> exposing > >>> > >> > >> >>> > > >>>> Protobuf by using bytes, would we want to change > >>> that > >>> > >> > >> >>> > > >>>> now? > >>> > >> > >> >>> > > >>>> > >>> > >> > >> >>> > > >>>> Best, > >>> > >> > >> >>> > > >>>> David > >>> > >> > >> >>> > > >>>> > >>> > >> > >> >>> > > >>>> On 10/16/19, Jacques Nadeau <jacq...@apache.org> > >>> > wrote: > >>> > >> > >> >>> > > >>>>> Hey David, > >>> > >> > >> >>> > > >>>>> > >>> > >> > >> >>> > > >>>>> RE: Async: I was trying to match the pattern we > >>> > >> > >> >>> > > >>>>> use > >>> > >> > >> >>> > > >>>>> for > >>> > >> > >> >>> > > >>>>> doget/doput > >>> > >> > >> >>> > > >>>>> for > >>> > >> > >> >>> > > >>>>> async. Yes, more thinking java given java grpc's > >>> > async > >>> > >> > >> >>> > > >>>>> always > >>> > >> > >> >>> > pattern. > >>> > >> > >> >>> > > >>>>> > >>> > >> > >> >>> > > >>>>> On the comment around the FlightData, I think it > >>> > >> > >> >>> > > >>>>> is > >>> > >> > >> >>> > > >>>>> overloading > >>> > >> > >> >>> > > >>>>> the > >>> > >> > >> >>> > > >>>> message > >>> > >> > >> >>> > > >>>>> to use metadata for this. If I want to send a > >>> control > >>> > >> > >> >>> > > >>>>> message > >>> > >> > >> >>> > > >>>> independently > >>> > >> > >> >>> > > >>>>> of the data message, I would have to define > >>> something > >>> > >> > >> >>> > > >>>>> like > >>> > >> > >> >>> > > >>>>> an > >>> > >> > >> >>> > > >>>>> empty > >>> > >> > >> >>> > > >>>> flight > >>> > >> > >> >>> > > >>>>> data message that has custom metadata. Why not > >>> > support > >>> > >> > >> >>> > > >>>>> a > >>> > >> > >> >>> > > >>>>> container > >>> > >> > >> >>> > > >>>>> object > >>> > >> > >> >>> > > >>>>> with a oneof{FlightData, Any} in it instead so > >>> users > >>> > >> > >> >>> > > >>>>> can > >>> > >> > >> >>> > > >>>>> add > >>> > >> > >> >>> > > >>>>> more > >>> > >> > >> >>> > data > >>> > >> > >> >>> > > >>>>> as > >>> > >> > >> >>> > > >>>>> desired. The default impl could be a noop for > >>> > >> > >> >>> > > >>>>> the > >>> Any > >>> > >> > >> >>> > > >>>>> messages. > >>> > >> > >> >>> > > >>>>> > >>> > >> > >> >>> > > >>>>> On Tue, Oct 15, 2019 at 6:50 PM David Li > >>> > >> > >> >>> > > >>>>> <li.david...@gmail.com> > >>> > >> > >> >>> > > >>>>> wrote: > >>> > >> > >> >>> > > >>>>> > >>> > >> > >> >>> > > >>>>>> Hi Jacques, > >>> > >> > >> >>> > > >>>>>> > >>> > >> > >> >>> > > >>>>>> Thanks for the comments. > >>> > >> > >> >>> > > >>>>>> > >>> > >> > >> >>> > > >>>>>> - I do agree DoExchange is a better name! > >>> > >> > >> >>> > > >>>>>> - FlightData already has metadata fields as a > >>> result > >>> > >> > >> >>> > > >>>>>> of > >>> > >> > >> prior > >>> > >> > >> >>> > > >>>>>> proposals, so I don't think we need a new > >>> > >> > >> >>> > > >>>>>> message > >>> to > >>> > >> > carry > >>> > >> > >> >>> > > >>>>>> that > >>> > >> > >> >>> > kind > >>> > >> > >> >>> > > >>>>>> of information. > >>> > >> > >> >>> > > >>>>>> - I like the suggestion of an async handler to > >>> > handle > >>> > >> > >> >>> > > >>>>>> incoming > >>> > >> > >> >>> > > >>>>>> messages as the fundamental API; it would > >>> > >> > >> >>> > > >>>>>> actually > >>> > be > >>> > >> > >> >>> > > >>>>>> quite > >>> > >> > >> >>> > natural > >>> > >> > >> >>> > > >>>>>> to > >>> > >> > >> >>> > > >>>>>> implement in Flight/Java. I will note that it's > >>> not > >>> > >> > >> >>> > > >>>>>> possible > >>> > >> > >> >>> > > >>>>>> in > >>> > >> > >> >>> > > >>>>>> C++/Python without spawning a thread, though. > >>> > >> > >> >>> > > >>>>>> (In > >>> > >> > essence, > >>> > >> > >> >>> > gRPC-Java > >>> > >> > >> >>> > > >>>>>> is async-always and gRPC-C++ is sync-always.) > >>> There > >>> > >> > >> >>> > > >>>>>> are > >>> > >> > >> >>> > experimental > >>> > >> > >> >>> > > >>>>>> C++ APIs that would let us do something similar > >>> > >> > >> >>> > > >>>>>> to > >>> > >> > >> >>> > > >>>>>> Java, > >>> > >> > >> >>> > > >>>>>> but > >>> > >> > >> >>> > > >>>>>> those > >>> > >> > >> >>> > > >>>>>> are > >>> > >> > >> >>> > > >>>>>> only in relatively recent gRPC versions and are > >>> > still > >>> > >> > >> >>> > > >>>>>> under > >>> > >> > >> >>> > > >>>>>> development (contrary to the interceptor APIs > >>> which > >>> > >> > >> >>> > > >>>>>> have > >>> > >> > >> been > >>> > >> > >> >>> > around > >>> > >> > >> >>> > > >>>>>> for quite a while). > >>> > >> > >> >>> > > >>>>>> > >>> > >> > >> >>> > > >>>>>> Thanks, > >>> > >> > >> >>> > > >>>>>> David > >>> > >> > >> >>> > > >>>>>> > >>> > >> > >> >>> > > >>>>>> On 10/15/19, Jacques Nadeau > >>> > >> > >> >>> > > >>>>>> <jacq...@apache.org> > >>> > >> > >> >>> > > >>>>>> wrote: > >>> > >> > >> >>> > > >>>>>>> I like it. Added some comments to the doc. > >>> > >> > >> >>> > > >>>>>>> Might > >>> > >> > >> >>> > > >>>>>>> worth > >>> > >> > >> >>> > > >>>>>>> discussion > >>> > >> > >> >>> > > >>>>>>> here > >>> > >> > >> >>> > > >>>>>>> depending on your thoughts. > >>> > >> > >> >>> > > >>>>>>> > >>> > >> > >> >>> > > >>>>>>> On Tue, Oct 15, 2019 at 7:11 AM David Li > >>> > >> > >> >>> > > >>>>>>> <li.david...@gmail.com> > >>> > >> > >> >>> > > >>>> wrote: > >>> > >> > >> >>> > > >>>>>>> > >>> > >> > >> >>> > > >>>>>>>> Hey Ryan, > >>> > >> > >> >>> > > >>>>>>>> > >>> > >> > >> >>> > > >>>>>>>> Thanks for the comments. > >>> > >> > >> >>> > > >>>>>>>> > >>> > >> > >> >>> > > >>>>>>>> Concrete example: I've edited the doc to > >>> provide a > >>> > >> > >> >>> > > >>>>>>>> Python > >>> > >> > >> >>> > strawman. > >>> > >> > >> >>> > > >>>>>>>> > >>> > >> > >> >>> > > >>>>>>>> Sync vs async: while I don't touch on it, you > >>> > could > >>> > >> > >> >>> > > >>>>>>>> interleave > >>> > >> > >> >>> > > >>>> uploads > >>> > >> > >> >>> > > >>>>>>>> and downloads if you were so inclined. Right > >>> now, > >>> > >> > >> >>> > > >>>>>>>> synchronous > >>> > >> > >> >>> > APIs > >>> > >> > >> >>> > > >>>>>>>> make this error-prone, e.g. if both client > >>> > >> > >> >>> > > >>>>>>>> and > >>> > >> > >> >>> > > >>>>>>>> server > >>> > >> > >> >>> > > >>>>>>>> wait > >>> > >> > >> >>> > > >>>>>>>> for > >>> > >> > >> >>> > each > >>> > >> > >> >>> > > >>>>>>>> other due to an application logic bug. (gRPC > >>> > >> > >> >>> > > >>>>>>>> doesn't > >>> > >> > >> >>> > > >>>>>>>> give > >>> > >> > >> >>> > > >>>>>>>> us > >>> > >> > >> >>> > > >>>>>>>> the > >>> > >> > >> >>> > > >>>>>>>> ability to have per-read timeouts, only an > >>> overall > >>> > >> > >> >>> > > >>>>>>>> timeout.) > >>> > >> > >> >>> > > >>>>>>>> As > >>> > >> > >> >>> > an > >>> > >> > >> >>> > > >>>>>>>> example of this happening with DoPut, see > >>> > >> > >> >>> > > >>>>>>>> ARROW-6063: > >>> > >> > >> >>> > > >>>>>>>> > >>> https://issues.apache.org/jira/browse/ARROW-6063 > >>> > >> > >> >>> > > >>>>>>>> > >>> > >> > >> >>> > > >>>>>>>> This is mostly tangential though, eventually > >>> > >> > >> >>> > > >>>>>>>> we > >>> > >> > >> >>> > > >>>>>>>> will > >>> > >> > >> >>> > > >>>>>>>> want > >>> > >> > >> >>> > > >>>>>>>> to > >>> > >> > >> >>> > design > >>> > >> > >> >>> > > >>>>>>>> asynchronous APIs for Flight as a whole. A > >>> > >> > bidirectional > >>> > >> > >> >>> > > >>>>>>>> stream > >>> > >> > >> >>> > > >>>>>>>> like > >>> > >> > >> >>> > > >>>>>>>> this (and like DoPut) just makes these > >>> > >> > >> >>> > > >>>>>>>> pitfalls > >>> > >> > >> >>> > > >>>>>>>> easier > >>> > >> > >> >>> > > >>>>>>>> to > >>> > >> > >> >>> > > >>>>>>>> run > >>> > >> > >> >>> > into. > >>> > >> > >> >>> > > >>>>>>>> > >>> > >> > >> >>> > > >>>>>>>> Using DoPut+DoGet: I discussed this in the > >>> > >> > >> >>> > > >>>>>>>> proposal, > >>> > >> > but > >>> > >> > >> >>> > > >>>>>>>> the > >>> > >> > >> >>> > main > >>> > >> > >> >>> > > >>>>>>>> concern is that depending on how you deploy, > >>> > >> > >> >>> > > >>>>>>>> two > >>> > >> > >> >>> > > >>>>>>>> separate > >>> > >> > >> >>> > > >>>>>>>> calls > >>> > >> > >> >>> > > >>>>>>>> could > >>> > >> > >> >>> > > >>>>>>>> get routed to different instances. > >>> > >> > >> >>> > > >>>>>>>> Additionally, > >>> > >> > >> >>> > > >>>>>>>> gRPC > >>> > >> > >> >>> > > >>>>>>>> has > >>> > >> > >> >>> > > >>>>>>>> some > >>> > >> > >> >>> > > >>>>>>>> reconnection behaviors; if the server goes > >>> > >> > >> >>> > > >>>>>>>> away > >>> in > >>> > >> > >> >>> > > >>>>>>>> between > >>> > >> > >> >>> > > >>>>>>>> the > >>> > >> > >> >>> > two > >>> > >> > >> >>> > > >>>>>>>> calls, but it then restarts or there is > >>> > >> > >> >>> > > >>>>>>>> another > >>> > >> > instance > >>> > >> > >> >>> > available, > >>> > >> > >> >>> > > >>>>>>>> the client will happily reconnect to the new > >>> > server > >>> > >> > >> without > >>> > >> > >> >>> > > >>>>>>>> warning. > >>> > >> > >> >>> > > >>>>>>>> > >>> > >> > >> >>> > > >>>>>>>> Thanks, > >>> > >> > >> >>> > > >>>>>>>> David > >>> > >> > >> >>> > > >>>>>>>> > >>> > >> > >> >>> > > >>>>>>>> On 10/15/19, Ryan Murray <rym...@dremio.com> > >>> > wrote: > >>> > >> > >> >>> > > >>>>>>>>> Hey David, > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> I think this proposal makes a lot of sense. > >>> > >> > >> >>> > > >>>>>>>>> I > >>> > like > >>> > >> > >> >>> > > >>>>>>>>> it > >>> > >> > >> >>> > > >>>>>>>>> and > >>> > >> > >> >>> > > >>>>>>>>> the > >>> > >> > >> >>> > > >>>>>>>>> possibility > >>> > >> > >> >>> > > >>>>>>>>> of remote compute via arrow buffers. One > >>> > >> > >> >>> > > >>>>>>>>> thing > >>> > >> > >> >>> > > >>>>>>>>> that > >>> > >> > >> >>> > > >>>>>>>>> would > >>> > >> > >> >>> > > >>>>>>>>> help > >>> > >> > >> >>> > me > >>> > >> > >> >>> > > >>>>>> would > >>> > >> > >> >>> > > >>>>>>>> be > >>> > >> > >> >>> > > >>>>>>>>> a concrete example of the API in a real life > >>> use > >>> > >> > >> >>> > > >>>>>>>>> case. > >>> > >> > >> >>> > > >>>>>>>>> Also, > >>> > >> > >> >>> > what > >>> > >> > >> >>> > > >>>>>> would > >>> > >> > >> >>> > > >>>>>>>> the > >>> > >> > >> >>> > > >>>>>>>>> client experience be in terms of sync vs > >>> > >> > >> >>> > > >>>>>>>>> asyc? > >>> > >> > >> >>> > > >>>>>>>>> Would > >>> > >> > >> >>> > > >>>>>>>>> the > >>> > >> > >> >>> > > >>>>>>>>> client > >>> > >> > >> >>> > > >>>>>>>>> block > >>> > >> > >> >>> > > >>>>>>>> till > >>> > >> > >> >>> > > >>>>>>>>> the bidirectional call return ie c = > >>> > >> > >> flight.vector_mult(a, > >>> > >> > >> >>> > > >>>>>>>>> b) > >>> > >> > >> >>> > or > >>> > >> > >> >>> > > >>>>>>>>> would > >>> > >> > >> >>> > > >>>>>>>> the > >>> > >> > >> >>> > > >>>>>>>>> client wait to be signaled that computation > >>> > >> > >> >>> > > >>>>>>>>> was > >>> > >> > >> >>> > > >>>>>>>>> done. > >>> > >> > >> >>> > > >>>>>>>>> If > >>> > >> > >> >>> > > >>>>>>>>> the > >>> > >> > >> >>> > > >>>>>>>>> later > >>> > >> > >> >>> > > >>>>>>>>> how > >>> > >> > >> >>> > > >>>>>>>>> is > >>> > >> > >> >>> > > >>>>>>>>> that different from a DoPut then DoGet? I > >>> suppose > >>> > >> > >> >>> > > >>>>>>>>> that > >>> > >> > >> >>> > > >>>>>>>>> this > >>> > >> > >> >>> > could > >>> > >> > >> >>> > > >>>> be > >>> > >> > >> >>> > > >>>>>>>>> implemented without extending the RPC > >>> > >> > >> >>> > > >>>>>>>>> interface > >>> > >> > >> >>> > > >>>>>>>>> but > >>> > >> > >> rather > >>> > >> > >> >>> > > >>>>>>>>> by a > >>> > >> > >> >>> > > >>>>>>>>> function/util? > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> Best, > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> Ryan > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> On Sun, Oct 13, 2019 at 9:24 PM David Li < > >>> > >> > >> >>> > li.david...@gmail.com> > >>> > >> > >> >>> > > >>>>>> wrote: > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>>> Hi all, > >>> > >> > >> >>> > > >>>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>>> We've been using Flight quite successfully > >>> > >> > >> >>> > > >>>>>>>>>> so > >>> > >> > >> >>> > > >>>>>>>>>> far, > >>> > >> > but > >>> > >> > >> we > >>> > >> > >> >>> > > >>>>>>>>>> have > >>> > >> > >> >>> > > >>>>>>>>>> identified a new use case on the horizon: > >>> being > >>> > >> > >> >>> > > >>>>>>>>>> able > >>> > >> > >> >>> > > >>>>>>>>>> to > >>> > >> > >> >>> > > >>>>>>>>>> both > >>> > >> > >> >>> > > >>>>>>>>>> send > >>> > >> > >> >>> > > >>>>>>>>>> and > >>> > >> > >> >>> > > >>>>>>>>>> retrieve Arrow data within a single RPC > >>> > >> > >> >>> > > >>>>>>>>>> call. > >>> To > >>> > >> > >> >>> > > >>>>>>>>>> that > >>> > >> > >> >>> > > >>>>>>>>>> end, > >>> > >> > >> >>> > I've > >>> > >> > >> >>> > > >>>>>>>>>> written up a proposal for a new RPC method: > >>> > >> > >> >>> > > >>>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>> > >>> > >> > >> >>> > > >>>>>> > >>> > >> > >> >>> > > >>>> > >>> > >> > >> >>> > > >>> > >> > >> > >>> > >> > > >>> > > >>> https://docs.google.com/document/d/1Hh-3Z0hK5PxyEYFxwVxp77jens3yAgC_cpp0TGW-dcw/edit?usp=sharing > >>> > >> > >> >>> > > >>>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>>> Please let me know if you can't view or > >>> comment > >>> > >> > >> >>> > > >>>>>>>>>> on > >>> > >> > the > >>> > >> > >> >>> > document. > >>> > >> > >> >>> > > >>>>>>>>>> I'd > >>> > >> > >> >>> > > >>>>>>>>>> appreciate any feedback; I think this is a > >>> > >> > >> >>> > > >>>>>>>>>> relatively > >>> > >> > >> >>> > > >>>>>>>>>> straightforward > >>> > >> > >> >>> > > >>>>>>>>>> addition - it is essentially > >>> > >> > >> >>> > > >>>>>>>>>> "DoPutThenGet". > >>> > >> > >> >>> > > >>>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>>> This is a format change and would require a > >>> > vote. > >>> > >> > I've > >>> > >> > >> >>> > > >>>>>>>>>> decided > >>> > >> > >> >>> > > >>>>>>>>>> to > >>> > >> > >> >>> > > >>>>>>>>>> table the other format change I had > >>> > >> > >> >>> > > >>>>>>>>>> proposed > >>> (on > >>> > >> > >> >>> > > >>>>>>>>>> DoPut), > >>> > >> > >> >>> > > >>>>>>>>>> as > >>> > >> > >> >>> > > >>>>>>>>>> it > >>> > >> > >> >>> > > >>>>>> doesn't > >>> > >> > >> >>> > > >>>>>>>>>> functionally change Flight, just the > >>> > >> > >> >>> > > >>>>>>>>>> interpretation > >>> > >> > of > >>> > >> > >> >>> > > >>>>>>>>>> the > >>> > >> > >> >>> > > >>>>>>>>>> semantics. > >>> > >> > >> >>> > > >>>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>>> Thanks, > >>> > >> > >> >>> > > >>>>>>>>>> David > >>> > >> > >> >>> > > >>>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> -- > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> Ryan Murray | Principal Consulting Engineer > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> +447540852009 | rym...@dremio.com > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>>> <https://www.dremio.com/> > >>> > >> > >> >>> > > >>>>>>>>> Check out our GitHub > >>> > >> > >> >>> > > >>>>>>>>> <https://www.github.com/dremio>, > >>> > >> > >> join > >>> > >> > >> >>> > > >>>>>>>>> our > >>> > >> > >> >>> > > >>>>>>>>> community > >>> > >> > >> >>> > > >>>>>>>>> site <https://community.dremio.com/> & > >>> Download > >>> > >> > Dremio > >>> > >> > >> >>> > > >>>>>>>>> <https://www.dremio.com/download> > >>> > >> > >> >>> > > >>>>>>>>> > >>> > >> > >> >>> > > >>>>>>>> > >>> > >> > >> >>> > > >>>>>>> > >>> > >> > >> >>> > > >>>>>> > >>> > >> > >> >>> > > >>>>> > >>> > >> > >> >>> > > >>>> > >>> > >> > >> >>> > > >>> > >>> > >> > >> >>> > > > > >>> > >> > >> >>> > > >>> > >> > >> >> > >>> > >> > >> > > >>> > >> > >> > >>> > >> > > > >>> > >> > > >>> > > > >>> > > >>> > >> > >
