Probably a better place to bring this up is as an issue on the GitHub tracker, as a feature request: https://github.com/grpc/grpc-java/issues
On Tuesday, June 11, 2019 at 12:40:18 PM UTC-7, Asad Ali wrote: > > bump. > > i am not sure if this was the right forum to bring this up. > any advice on who/where to continue this conversation with is much > appreciated.. > > -A > > On Friday, June 7, 2019 at 4:21:58 PM UTC-7, Asad Ali wrote: >> >> tl;dr >> >> This is a followup from a discussion that was initiated on gitter >> grpc/grpc channel. >> Currently the grpc/java library reuses the User-Agent from the channel >> for each RPC >> and discards User-Agent by treating it as a reserved header. >> >> However, User-Agent is not a reserved header and this creates >> complications >> when trying to write a proxy-like gRPC service for HTTP endpoints that >> care >> about User-Agent for response customization. >> >> Posting it here to get more ideas about how to resolve this. >> >> quoting the conversation below: >> >> Asad @asadali Jun 04 13:10 >> What was the underlying reason for the restriction on not allowing >> User-Agent >> to be overridden on a per-call basis? can't seem to find a spec which >> reserves >> the User-Agent string for gRPC/HTTP2 and yet there is code in place in the >> libraries (grpc-java/ grpc-go ..) to discard any user-supplied metadata >> regarding User-Agent and always use the channel's value eg: >> Utils.convertServerHeaders >> >> Asad @asadali Jun 04 13:16 >> use-case: >> client ---> httpSVC-A ---> grpcSVC-B ---> httpSVC-C >> how can the client's user-agent be conveyed to httpSVC-C? if A-B have >> ONLY one >> channel open between them with a channel-level User-Agent that can't be >> overridden >> @ejona86 ^ question regarding user-agent behavior >> >> Eric Anderson @ejona86 Jun 04 14:34 >> @asadali, user-agent is a built-in feature as gRPC itself sends it. >> There is >> an API to change what gRPC sends, but there didn't seem to be any need to >> allow >> it to be changed per-RPC. >> >> Asad @asadali Jun 04 14:43 >> @ejona86 we seem to have a use-case in which a per-RPC user-agent will >> make >> things easier for us. The alternate is to use custom metadata fields to >> preserve this information. that approach seems non-standard and we were >> hoping >> to avoid it. Will it be possible to include a per-RPC user-agent in >> gRPC? i >> will be happy to code it up. but based on what i read in past issues, this >> request was repeatedly turned down. >> >> Eric Anderson @ejona86 Jun 04 14:44 >> That is a cross-language decision. You would need to make clear what the >> use-case for it is. Right now, it isn't clear what the use-case is. >> Oh. I see now. >> You want to communicate the origin client's user-agent to SVC-C >> Yeah. That's not appropriate for user-agent. >> >> Asad @asadali Jun 04 14:45 >> ack >> >> Eric Anderson @ejona86 Jun 04 14:46 >> .... unless you are making something closer to a proxy. Maybe. It sort of >> seems like a can of worms. It just makes a mess of things. >> But I think I understand now. >> >> Asad @asadali Jun 04 14:48 >> so the intermediate gateways aren't pure proxies but maybe more like >> aggregators. in the non-GRPC world, the implementation made an assumption >> that >> User-Agent is the originating client's user-agent. and all intermediate >> hops >> honored that. I agree, that this is a very loose reading of the spec. I >> feel >> the more logical method is to update the user-agent on each hop >> however, systems built around that assumption aren't happy when they lose >> this >> info :( IMO, gRPC clients can default to per-channel behavior but the >> choice >> should ultimately be left to the user if they want to override it >> >> Eric Anderson @ejona86 Jun 04 14:51 >> Well, today the application can't set the entire user-agent. gRPC will >> always >> include itself in the user-agent. I'm trying to check what HTTP says to >> do for >> user-agent and proxies. >> >> Asad @asadali Jun 04 14:52 >> yeah i can use another opinion on this. and current gRPC behavior is what >> I am >> trying to rationalize. does it need to always include its user-agent? >> >> Eric Anderson @ejona86 Jun 04 17:31 >> @asadali, proxies do forward the user-agent. We do want to enable grpc >> proxies, >> so that does mean we should forward the user-agent. Although on the >> server, any >> compatibility quirks would generally be with the proxy, not the >> end-client. So >> it still seems muddled, but it does seem we should consider it. >> >> >> >>> -- You received this message because you are subscribed to the Google Groups "grpc.io" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/grpc-io/1a4a2f68-18f4-4295-815b-df0aef8ca63b%40googlegroups.com.
