I would like to propose a 'reuse connection' URI scheme for Flight RPC. This proposal was previously discussed at [1]. A candidate implementation for C++, Java, and Go is at [2].
The vote will be open for at least 72 hours. [ ] +1 [ ] +0 [ ] -1 Do not accept this proposal because... [1]: https://lists.apache.org/thread/pc9fs0hf8t5ylj9os00r9vg8d2xv2npz [2]: https://github.com/apache/arrow/pull/40084 On Tue, Feb 20, 2024, at 14:14, David Li wrote: > Thanks for the comments - I've updated the implementation [1] and added > Go + integration tests. If this all checks out I'd like to start a vote > soon. > > [1]: https://github.com/apache/arrow/pull/40084 > > On Fri, Feb 16, 2024, at 13:43, Andrew Lamb wrote: >> Thank you -- I think the usecase is great, but agree with the other >> reviewers that the name may be confusing. I left some notes on the ticket >> >> Andrew >> >> On Wed, Feb 14, 2024 at 3:52 PM David Li <lidav...@apache.org> wrote: >> >>> I've put up a candidate implementation sans integration test [1]. >>> >>> Some caveats: >>> - java.net.URI doesn't accept 'scheme://', only 'scheme:/' or 'scheme://?' >>> (yes, an empty query string pacifies it). I've chosen the latter since the >>> former is technically a URI with a non-empty path but neither are ideal. >>> - I've changed the scheme to 'arrow-flight-reuse-connection' to be more >>> faithful to the intended use than 'fallback'. >>> >>> [1]: https://github.com/apache/arrow/pull/40084 >>> >>> On Tue, Feb 13, 2024, at 13:01, Jean-Baptiste Onofré wrote: >>> > Hi David, >>> > >>> > It's reasonable. I think we can start with your initial proposal (it >>> > sounds fine to me) and we can always improve step by step. >>> > >>> > Thanks ! >>> > Regards >>> > JB >>> > >>> > On Tue, Feb 13, 2024 at 4:53 PM David Li <lidav...@apache.org> wrote: >>> >> >>> >> I'm going to keep the proposal as-is then. It can be extended if this >>> use case comes up. >>> >> >>> >> I'll start work on candidate implementations now. >>> >> >>> >> On Tue, Feb 13, 2024, at 03:22, Antoine Pitrou wrote: >>> >> > I think the original proposal is sufficient. >>> >> > >>> >> > Also, it is not obvious to me how one would switch from e.g. grpc+tls >>> to >>> >> > http without an explicit server location (unless both Flight servers >>> are >>> >> > hosted under the same port?). So the "+" proposal seems a bit weird. >>> >> > >>> >> > >>> >> > Le 12/02/2024 à 23:39, David Li a écrit : >>> >> >> The idea is that the client would reuse the existing connection, in >>> which case the protocol and such are implicit. (If the client doesn't have >>> a connection anymore, it can't use the fallback anyways.) >>> >> >> >>> >> >> I suppose this has the advantage that you could "fall back" to a >>> known hostname with a different protocol, but I'm not sure that always >>> applies anyways. (Correct me if I'm wrong Matt, but as I recall, UCX >>> addresses aren't hostnames but rather opaque byte blobs, for instance.) >>> >> >> >>> >> >> If we do prefer this, to avoid overloading the hostname, there's >>> also the informal convention of using + in the scheme, so it could be >>> arrow-flight-fallback+grpc+tls://, arrow-flight-fallback+http://, etc. >>> >> >> >>> >> >> On Mon, Feb 12, 2024, at 17:03, Joel Lubinitsky wrote: >>> >> >>> Thanks for clarifying. >>> >> >>> >>> >> >>> Given the relationship between these two proposals, would it also be >>> >> >>> necessary to distinguish the scheme (or schemes) supported by the >>> >> >>> originating Flight RPC service? >>> >> >>> >>> >> >>> If that is the case, it may be preferred to use the "host" portion >>> of the >>> >> >>> URI rather than the "scheme" to denote the location of the data. In >>> this >>> >> >>> scenario, the host "0.0.0.0" could be used. This IP address is >>> defined in >>> >> >>> IETF RFC1122 [1] as "This host on this network", which seems most >>> >> >>> consistent with the intended use-case. There are some caveats to >>> this usage >>> >> >>> but in my experience it's not uncommon for protocols to extend the >>> >> >>> definition of this address in their own usage. >>> >> >>> >>> >> >>> A benefit of this convention is that the scheme remains available >>> in the >>> >> >>> URI to specify the transport available. For example, the following >>> list of >>> >> >>> locations may be included in the response: >>> >> >>> >>> >> >>> ["grpc://0.0.0.0", "ucx://0.0.0.0", "grpc://1.2.3.4", >>> <other_locations>...] >>> >> >>> >>> >> >>> This would indicate that grpc and ucx transport is available from >>> the >>> >> >>> current service, grpc is available at 1.2.3.4, and possibly more >>> >> >>> combinations of scheme/host. >>> >> >>> >>> >> >>> [1] https://datatracker.ietf.org/doc/html/rfc1122#section-3.2.1.3 >>> >> >>> >>> >> >>> On Mon, Feb 12, 2024 at 2:53 PM David Li <lidav...@apache.org> >>> wrote: >>> >> >>> >>> >> >>>> Ah, while I was thinking of it as useful for a fallback, I'm not >>> >> >>>> specifying it that way. Better ideas for names would be >>> appreciated. >>> >> >>>> >>> >> >>>> The actual precedence has never been specified. All endpoints are >>> >> >>>> equivalent, so clients may use what is "best". For instance, with >>> Matt >>> >> >>>> Topol's concurrent proposal, a GPU-enabled client may >>> preferentially try >>> >> >>>> UCX endpoints while other clients may choose to ignore them >>> entirely (e.g. >>> >> >>>> because they don't have UCX installed). >>> >> >>>> >>> >> >>>> In practice the ADBC/JDBC drivers just scan the list left to right >>> and try >>> >> >>>> each endpoint in turn for lack of a better heuristic. >>> >> >>>> >>> >> >>>> On Mon, Feb 12, 2024, at 14:28, Joel Lubinitsky wrote: >>> >> >>>>> Thanks for proposing this David. >>> >> >>>>> >>> >> >>>>> I think the ability to include the Flight RPC service itself in >>> the list >>> >> >>>> of >>> >> >>>>> endpoints from which data can be fetched is a helpful addition. >>> >> >>>>> >>> >> >>>>> The current choice of name for the URI (arrow-flight-fallback://) >>> seems >>> >> >>>> to >>> >> >>>>> imply that there is an order of precedence that should be >>> considered in >>> >> >>>> the >>> >> >>>>> list of URI’s. Specifically, as a developer receiving the list of >>> >> >>>> locations >>> >> >>>>> I might assume that I should try fetching from other locations >>> first. If >>> >> >>>>> those do not succeed, I may try the original service as a >>> fallback. >>> >> >>>>> >>> >> >>>>> Are these the intended semantics? If so, is there a way to >>> include the >>> >> >>>>> original service in the list of locations without the implied >>> precedence? >>> >> >>>>> >>> >> >>>>> Thanks, >>> >> >>>>> Joel >>> >> >>>>> >>> >> >>>>> On Mon, Feb 12, 2024 at 11:52 James Duong < >>> james.du...@improving.com >>> >> >>>> .invalid> >>> >> >>>>> wrote: >>> >> >>>>> >>> >> >>>>>> This seems like a good idea, and also improves consistency with >>> clients >>> >> >>>>>> that erroneously assumed that the service endpoint was always in >>> the >>> >> >>>> list >>> >> >>>>>> of endpoints. >>> >> >>>>>> >>> >> >>>>>> From: Antoine Pitrou <anto...@python.org> >>> >> >>>>>> Date: Monday, February 12, 2024 at 6:05 AM >>> >> >>>>>> To: dev@arrow.apache.org <dev@arrow.apache.org> >>> >> >>>>>> Subject: Re: [DISCUSS] Flight RPC: add 'fallback' URI scheme >>> >> >>>>>> >>> >> >>>>>> Hello, >>> >> >>>>>> >>> >> >>>>>> This looks fine to me. >>> >> >>>>>> >>> >> >>>>>> Regards >>> >> >>>>>> >>> >> >>>>>> Antoine. >>> >> >>>>>> >>> >> >>>>>> >>> >> >>>>>> Le 12/02/2024 à 14:46, David Li a écrit : >>> >> >>>>>>> Hello, >>> >> >>>>>>> >>> >> >>>>>>> I'd like to propose a slight update to Flight RPC to make >>> Flight SQL >>> >> >>>>>> work better in different deployment scenarios. Comments on the >>> doc >>> >> >>>> would >>> >> >>>>>> be appreciated: >>> >> >>>>>>> >>> >> >>>>>>> >>> >> >>>>>> >>> >> >>>> >>> https://docs.google.com/document/d/1g9M9FmsZhkewlT1mLibuceQO8ugI0-fqumVAXKFjVGg/edit?usp=sharing >>> >> >>>>>>> >>> >> >>>>>>> The gist is that FlightEndpoint allows specifying either (1) a >>> list of >>> >> >>>>>> concrete URIs to fetch data from or (2) no URIs, meaning to >>> fetch from >>> >> >>>> the >>> >> >>>>>> Flight RPC service itself; but it would be useful to combine both >>> >> >>>> behaviors >>> >> >>>>>> (try these concrete URIs and fall back to the Flight RPC service >>> itself) >>> >> >>>>>> without requiring the service to know its own public address. >>> >> >>>>>>> >>> >> >>>>>>> Best, >>> >> >>>>>>> David >>> >> >>>>>> >>> >> >>>> >>>
