feat(xds): initial crate structure

Cargo.toml

@@ -13,6 +13,7 @@ members = [
   "examples",
   "codegen",
   "grpc",
+  "xds-client",
   "interop", # Tests
   "tests/disable_comments",
   "tests/wellknown",

xds-client/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "xds-client"
+description = "An xDS client implementation in Rust"
+version = "0.1.0-alpha.1"
+edition = "2021"
+homepage = "https://github.com/hyperium/tonic"
+repository = "https://github.com/hyperium/tonic"
+license = "MIT"
+rust-version = { workspace = true }
+
+[lints]
+workspace = true
+
+[dependencies]
+
+[features]
+default = ["transport-tonic"]
+transport-tonic = ["rt-tokio", "codegen-prost"]
+rt-tokio = []
+codegen-prost = []

xds-client/src/client/mod.rs

@@ -0,0 +1 @@
+//! Client interface through which the user can watch and receive updates for xDS resources.

xds-client/src/error.rs

@@ -0,0 +1 @@
+//! Error types for the xDS client.

xds-client/src/lib.rs

@@ -0,0 +1,13 @@
+//! A Rust implementation of [xDS](https://www.envoyproxy.io/docs/envoy/latest/api-docs/xds_protocol) client.
+//!
+//! # Feature Flags
+//!
+//! - `transport-tonic`: Enables the use of the `tonic` transport. This enables `rt-tokio` and `codegen-prost` features. Enabled by default.
+//! - `rt-tokio`: Enables the use of the `tokio` runtime. Enabled by default.
+//! - `codegen-prost`: Enables the use of the `prost` codec generated resources. Enabled by default.
+
+pub mod client;
+pub mod error;
+pub mod resource;
+pub mod runtime;
+pub mod transport;

xds-client/src/resource/mod.rs

@@ -0,0 +1,4 @@
+//! Provides abstraction for xDS resources.
+
+#[cfg(feature = "codegen-prost")]
+pub mod prost;

xds-client/src/resource/prost.rs

@@ -0,0 +1 @@
+//! `prost` codec-specific resources.

xds-client/src/runtime/mod.rs

@@ -0,0 +1,4 @@
+//! Provides abstraction for async runtimes.
+
+#[cfg(feature = "rt-tokio")]
+pub mod tokio;

xds-client/src/runtime/tokio.rs

@@ -0,0 +1 @@
+//! `tokio` based runtime implementation.

xds-client/src/transport/mod.rs

@@ -0,0 +1,4 @@
+//! Provides abstraction for transport layers.
+
+#[cfg(feature = "transport-tonic")]
+pub mod tonic;

xds-client/src/transport/tonic.rs

@@ -0,0 +1 @@
+//! `tonic` based transport implementation.