Currently, the mock controller, which is used in tests, takes all of its
updates a priori, which makes it hard to control when an update occurs within a
test.
Now, the controller exposes a `DstSender`, which wraps an unbounded channel of
destination updates. This allows tests to trigger updates at a specific point
in the test.
In order to accomplish this, the controller's hand-rolled gRPC server
implementation has been discarded in favor of a real gRPC destination service.
This requires that the `controller-grpc` project now builds both clients
and servers for the destination service. Additionally, we now build a tap
client as well (assuming that we'll want to write tests against our tap
server).
The proxy depends on `protoc`-generated gRPC bindings to communicate
with the controller. In order to generate these bindings, build-time
dependencies must be compiled.
In order to support a more granular, cacheable build scheme, a new crate
has been created to house these gRPC bindings,
`conduit-proxy-controller-grpc`.
Because `TryFrom` and `TryInto` conversions are implemented for
protobuf-defined types, the `convert` module also had to be moved to
into a dedicated crate.
Furthermore, because the proxy's tests require that
`quickcheck::Aribtrary` be implemented for protobuf types, the
`conduit-proxy-controller-grpc` crate supports an _arbitrary_ feature
fla protobuf types, the `conduit-proxy-controller-grpc` crate supports
an _arbitrary_ feature flag.
While we're moving these libraries around, the `tower-router` crate has
been moved to `proxy/router` and renamed to `conduit-proxy-router.`
`futures-mpsc-lossy` has been moved into the proxy directory but has not
been renamed.
Finally, the `proxy/Dockerfile-deps` image has been updated to avoid the
wasteful building of dependency artifacts, as they are not actually used
by `proxy/Dockerfile`.
Oliver Gould