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 >> >> >>>>>> >> >> >>>> >>
