Tonic: Need a way to log specific message in interceptor

[dansgithubuser]

Feature Request

Motivation

Similar to typical web server log, just want a way to have a record of what's come in.

Proposal

Something like into_inner that doesn't move the request? I'm unclear on the larger architecture.

[dansgithubuser]

discord context: https://discordapp.com/channels/500028886025895936/628706823104626710/702239976602992691

[LucioFranco]

Yup, so basically if I understand correctly we want some way to know the type of the request and the service its on so we can correlate logs with that. Currently, with the Request<()> type you don't know what service or handler it is.

[ajguerrer]

@dansgithubuser Maybe you want get_ref?

Following the tracing example, you could do something like:

tracing::info!(messsage = ?request.get_ref());

[dansgithubuser]

@ajguerrer I'm not sure I'm following. Calling get_ref on a Request<()> gets me a &(). I want an interceptor to write generic log logic, like "gRPC server got request: {}" similar to a web server. Right now I write a log statement per handler.

The tracing example, if I understand correctly, shows me how to use spans for tracing. But I don't see where the interceptor (or some generic place to put code) is?

[LucioFranco]

Currently, this is not possible at the interceptor level. We plan on adding this type of feature.

For now you can write a tower service layer that intercepts at the http2 level and use the path in there to log the service and rpc.

[LucioFranco]

There is now a tower example https://github.com/hyperium/tonic/blob/master/examples/src/tower/server.rs, closing this, feel free to re-open if you have anymore questions!

[saschagrunert]

There is now a tower example https://github.com/hyperium/tonic/blob/master/examples/src/tower/server.rs, closing this, feel free to re-open if you have anymore questions!

If I collect the body into a Vec<u8>, how can I get the typed request message from it? :innocent:

[LucioFranco]

@saschagrunert what do you mean by typed request message?

[saschagrunert]

@saschagrunert what do you mean by typed request message?

My main goal was to automatically trace the request and print their fields. If I create a tower interceptor I can collect the body as Vec. But how do I get this vector to be represented as my proto message type? 💁🏻‍♂️ Maybe adding a trace log to each RPC is indeed the more easy solution here.

[LucioFranco]

I personally would go the route of per rpc method. There is a reason that the interceptor is limited. It is because it gets called before we even receive the body. So I think the later solution works the best or else you will do many avoidable copies and slowing everything down.

[saschagrunert]

Yes thank you for the clarification. I also thought waiting for the whole body and collecting it in a vector might have a bigger performance impact. I’ll stick to the typed RPC approach. 👍