Enable adding the gRPC API to tonic without serving

[maximelenoir]

What problem are you trying to solve?

I would like the Server to optionally serve the InstrumentServer after it's been added as a service to the tonic Builder. As of now, the Server implementation starts the aggregator, add the service to tonic and start the gRPC service. Ideally, this last step could be optional, leaving the user the choice of adding more services or using this tonic service in a larger set of services: in my case, I would like to transform the tonic service to a tower service and multiplex it with an Axum service.

How should the problem be solved?

Probably by extending the Service API so that the aggregation is started and the InstrumentService is properly added to tonic, returning a tonic Router. I have a fork that I'm using for production here: 700b80a

There can be a few drawbacks with this:

• The builder can be configured with a listening port / Unix socket so it might feel surprising to have an API that completely ignores it
• We lose the fine grained control of the aggregator thread handle (either by dropping it in this new API body or by leaking it to the user)

Any alternatives you've considered?

I did not consider another solution yet.

How would users interact with this feature?

No response

Would you like to work on this feature?

maybe

[hds]

I've been thinking about this issue and your use case and I think I have a solution.

I'm going to need a bit more time to work through it though.

I just wanted to let you know that this issue hasn't fallen on deaf ears.

[maximelenoir]

Wonderful! Thanks a lot for your work