I'm out of town this week (vacation) and will be reviewing your feedback next week. Thanks for the feedback!
On Thu, Aug 9, 2018, 8:45 PM Wes McKinney <wesmck...@gmail.com> wrote: > hi folks, > > I left some feedback on this PR. If others could take a look > (particularly at the .proto service definition) that would be useful. > > We should decide on an approach to getting multiple production-worthy > Flight/RPC implementations ready to go. It would be a good goal to > deliver (end-to-end send/receive data between Python and Java, or > Python and other Python processes) in the next couple releases. > > - Wes > > On Wed, May 30, 2018 at 12:44 PM, Jacques Nadeau <jacq...@apache.org> > wrote: > > Correct, I'm maintaining standard protobuf encoding so a consumer that > > doesn't go byte by byte can still consumer/produce the messages. > > > > More impls: for sure. > > > > On Wed, May 30, 2018 at 9:01 AM, Wes McKinney <wesmck...@gmail.com> > wrote: > > > >> I see; looking more closely I see you've sidestepped the standard > >> Protobuf serialization to write the stream as tagged components: > >> > >> https://github.com/apache/arrow/compare/master...jacques-n:flight#diff- > >> 02cfc9235e22653fce8a7636c9f95507R241 > >> > >> and then reading the fields of the message tag by tag > >> > >> https://github.com/apache/arrow/compare/master...jacques-n:flight#diff- > >> 02cfc9235e22653fce8a7636c9f95507R159 > >> > >> Would it be correct that if a GRPC implementation doesn't provide > >> sufficient access to the byte stream (or if it doesn't care enough > >> about zero copy) that you could allow GRPC to return an instance of > >> the FlightData structure? > >> > >> I expect we'd want to see a few interoperable implementations (I > >> suggest Java, C++, Go) to harden the fine details. > >> > >> - Wes > >> > >> On Mon, May 28, 2018 at 3:32 PM, Jacques Nadeau <jacq...@apache.org> > >> wrote: > >> > Cutting through the layers of GRPC will be a per language approach > thing. > >> > Assuming that each GRPC language implementation does a good job of > >> > separating message encapsulation from the base library, this should be > >> > straight-forward-ish. Hope improves around this as I see creation of > >> > non-protobuf protocols built on top of the base GRPC [1]. How to do > this > >> in > >> > each language will probably take time looking at the GRPC internals > for > >> > that language but can be a secondary step once you get the protocol > >> working > >> > (you can just pay for extra copies until then). > >> > > >> > In my Java approach I believe I do one read copy and zero write copies > >> > (needs more testing) which was my target. (Getting to zero-copy on > read > >> > means a lot more complexity because your socket-reading has to be > >> protocol > >> > aware: even our bespoke layer in Dremio doesn't try to do that. I'd > guess > >> > KRPC does the same but haven't reviewed the code to confirm.) > >> > > >> > Will try to get some more slides/readme and a proper proposed patch up > >> soon. > >> > > >> > [1] https://grpc.io/blog/flatbuffers > >> > > >> > > >> > > >> > On Mon, May 28, 2018 at 1:05 AM, Wes McKinney <wesmck...@gmail.com> > >> wrote: > >> > > >> >> hey Jacques, > >> >> > >> >> This is great news, I look forward to digging into this. My biggest > >> >> initial question is the Protobuf encapsulation, specifically: > >> >> > >> >> https://github.com/jacques-n/arrow/blob/flight/java/flight/ > >> >> src/main/protobuf/flight.proto#L99 > >> >> > >> >> My understanding of Protocol Buffers is that on read, the "data_body" > >> >> memory would be copied out of the serialized protobuf that came > across > >> >> the wire. Your comment in the .proto says this "comes last in the > >> >> definition to help with sidecar patterns" -- my read is that it would > >> >> be up to us to do our own sidecar implementation, similar to how > >> >> Apache Kudu has zero-copy sidecars in their KRPC system [1] (the > >> >> comment there describes pretty much exactly the problem we have). I > >> >> saw that you also replied on a GRPC thread about this issue [2]. > Could > >> >> you summarize what (if anything) stands in the way to get zero-copy > on > >> >> write and read? > >> >> > >> >> - Wes > >> >> > >> >> [1]: https://github.com/apache/kudu/blob/master/src/kudu/rpc/ > >> >> rpc_sidecar.h#L34 > >> >> [2]: https://github.com/grpc/grpc-java/issues/1054#issuecomment- > >> 391692087 > >> >> > >> >> On Thu, May 24, 2018 at 6:57 AM, Jacques Nadeau <jacq...@apache.org> > >> >> wrote: > >> >> > FYI, if you want to see an example server you can run with a GRPC > >> >> generated > >> >> > client, you can run the ExampleFlightServer located at [1]. Very > basic > >> >> > 'test' with that class and client is located at [2]. > >> >> > > >> >> > [1] > >> >> > https://github.com/jacques-n/arrow/tree/flight/java/flight/ > >> >> src/main/java/org/apache/arrow/flight/example > >> >> > [2] > >> >> > https://github.com/jacques-n/arrow/blob/flight/java/flight/ > >> >> src/test/java/org/apache/arrow/flight/example/TestExampleServer.java > >> >> > > >> >> > > >> >> > On Thu, May 24, 2018 at 11:51 AM, Jacques Nadeau < > jacq...@apache.org> > >> >> wrote: > >> >> > > >> >> >> Hey All, > >> >> >> > >> >> >> I used my Strata talk today as a forcing function to make > additional > >> >> >> progress on a GRPC-based Arrow RPC protocol [1]. I’m calling it > >> “Apache > >> >> >> Arrow Flight”. You can take a look at the work here [2]. I’ll > work to > >> >> clean > >> >> >> up my work and explain my thoughts about the protocol in the > coming > >> >> days. > >> >> >> High-level: use protobuf as a encapsulation format so that any > client > >> >> that > >> >> >> is supported in GRPC will work. However, we can optimize the > >> read/write > >> >> >> path for targeted languages and hand control the > >> >> >> serialization/deserialization and memory handling. (I did that in > >> this > >> >> Java > >> >> >> patch [3][4][5].) I also looked at starting to use GRPC generated > >> >> bindings > >> >> >> within Python but it looks like some glue code may be needed in > the > >> C++ > >> >> >> layer since Python delegates down frequently. I also am still > trying > >> to > >> >> >> understand GRPC back-pressure patterns and whether the protocol > >> >> >> realistically needs to change to cover real-world high performance > >> use > >> >> >> cases. > >> >> >> > >> >> >> I’ll send out some slides about the ideas and update README, etc. > >> soon. > >> >> >> > >> >> >> Thanks, > >> >> >> Jacques > >> >> >> > >> >> >> [1] https://github.com/jacques-n/arrow/blob/flight/java/flight/ > >> >> >> src/main/protobuf/flight.proto > >> >> >> [2] http://github.com/jacques-n/arrow/ > >> >> >> [3] https://github.com/jacques-n/arrow/tree/flight/ > >> >> >> java/flight/src/main/java/org/apache/arrow/flight/grpc > >> >> >> [4] https://github.com/jacques-n/arrow/blob/flight/ > >> >> >> java/flight/src/main/java/org/apache/arrow/flight/ > >> >> ArrowMessage.java#L253 > >> >> >> <https://github.com/jacques-n/arrow/blob/flight/java/flight/ > >> >> src/main/java/org/apache/arrow/flight/ArrowMessage.java#L253> > >> >> >> [5] https://github.com/jacques-n/arrow/blob/flight/ > >> >> >> java/flight/src/main/java/org/apache/arrow/flight/ > >> >> ArrowMessage.java#L185 > >> >> >> > >> >> >> > >> >> > >> >
