feat(transport): add support for uds, unix domain socket

[adamcavendish]

Commit Message

Previously the uds support lives as an example in the example/src/uds folder. Endpoint is refactored to support multiple endpoint types, including Uri and Uds.

The supported unix domain socket URI follows RFC-3986 which is aligned with the gRPC naming convention.

• unix:relative_path
• unix:///absolute_path

References:

• https://datatracker.ietf.org/doc/html/rfc3986
• https://github.com/grpc/grpc/blob/master/doc/naming.md

Motivation

• Previously required custom connectors and explicit tower dependencies for UDS. Uds Connector Example

• Users can now use the same connect() API for both TCP and UDS:

  let client = GreeterClient::connect("unix:///tmp/tonic/helloworld").await?;

Solution

1. To implement the feature, Endpoint is refactored support multiple endpoint types:

   +#[derive(Clone, PartialEq, Eq, Hash)]
   +pub(crate) enum EndpointType {
   +    Uri(Uri),
   +    Uds(String),
   +}
   +
    /// Channel builder.
    ///
    /// This struct is used to build and configure HTTP/2 channels.
    #[derive(Clone)]
    pub struct Endpoint {
   -    pub(crate) uri: Uri,
   +    pub(crate) uri: EndpointType,
   +    fallback_uri: Uri,

2. To satisfy the backward compatibility of Endpoint::uri() method, the fallback_uri attribute is added and returned when user working with uds mode so the method will still be able to return a &Uri.

        pub fn uri(&self) -> &Uri {
   -        &self.uri
   +        match &self.uri {
   +            EndpointType::Uri(uri) => uri,
   +            EndpointType::Uds(_) => &self.fallback_uri,
   +        }
        }

[adamcavendish]

@tottoto @LucioFranco Please help review when you are available. Thanks!

[adamcavendish]

@tottoto @LucioFranco Kindly ping here to get some reviews and CI running. Thanks!

[adamcavendish]

The UdsConnector is the core part of this pull request.

[adamcavendish]

I have rebased to the latest master. @tottoto @LucioFranco would you like to have some discussions?

[LucioFranco]

This is unfortunate, this removes the ability to use the shared attributes because you allocate anyways. Can we just check the bytes instead of converting it to a string?

[LucioFranco]

Overall LGTM a few nits and CI to fix

[LucioFranco]

I will push some changes to get this over the finish line since I have some time right now.

[adamcavendish]

@LucioFranco Thanks for your revisions on making it work on Windows platforms. I really appreciated it.