Feature: Sharing connection between service clients

[drmontgomery]

Most gRPC client libraries allow multiple service clients to share a single HTTP connection to a server. This is typically presented as a separate "channel" abstraction, which used to initialize the service client. (For example, see https://grpc.io/docs/languages/java/basics/#client)

In akka-grpc, on the other hand, each service client creates its own connection to the server (via creating a ClientState, which creates an InternalChannel). While this works, it does mean that an akka-grpc client that uses multiple services will use many more HTTP connections than clients using other gRPC implementations. In some contexts (e.g. load testing), this difference can be significant.

Would it be possible to add support for reusing a single HTTP connection with multiple service clients? I think exposing a channel abstraction, like other gRPC libraries, would be best, since it allows the library user to control how connections are shared between services.

[drmontgomery]

Added pull request as a more concrete example of what I'm proposing.

[raboof]

The feature has been merged, but we'd stll like to add a code example to the docs - perhaps let's leave the issue open for that?