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 >>>>>> >>>>
