Add gRPC reverse proxy server example

[trustin]

.. which is similar to our HTTP reverse proxy server example.

[anuraaga]

@trustin Could you define more what a gRPC reverse proxy is? Would it just be a normal service implementation that delegates to another stub? In general, I make reverse proxies for gRPC services by using a normal HTTP reverse proxy since it's not dependent on the stub's definition.

[ikhoon]

It was originally requested in https://line-armeria.slack.com/archives/C1NGPBUH2/p1577719334033400

[anuraaga]

Thanks for the link! It does look like the original request was just for a normal HTTP proxy so maybe we already have the example, or it could be extended with rule matching.

For reference, here's an Armeria reverse proxy that allows simple path-based routing (perfect for gRPC) - https://github.com/curioswitch/curiostack/tree/master/gateway/server

[antongocode]

Apologies for commenting on a fairly old ticket, but where can I find the HTTP reverse proxy examples for armeria? This ticket is the top search result.

[ikhoon]

@antongocode You might want to see https://github.com/line/armeria-examples/blob/master/proxy-server/src/main/java/example/armeria/proxy/ProxyService.java

[roeniss]

Is there any work left to be done on this issue? As anuraaga said it's not obvious what reverse proxy for gprc is compared to normal one. To be more specific, I wonder why this issue got good first issue tag later.

[jrhee17]

I'm not sure what the original request was as the slack post seems to have expired. Having said this, I think it could be meaningful if we can add an example of a grpc-gateway type reverse-proxy implementation using armeria's grpc-json transcoding features.

[roeniss]

I'll try it, thank you for the advice @jrhee17

[roeniss]

After half a year, I realize that I don't want to resolve this issue. Sorry for others who wanted to take this issue for such a delayed decision

[Bue-von-hon]

I'll create a PR for this issue until this weekend 🙂