enhancement(api): add dynamic API router based on runtime state

lib/saluki-api/Cargo.toml

@@ -12,3 +12,4 @@ workspace = true
 axum = { workspace = true, features = ["http1", "tokio"] }
 axum-extra = { workspace = true, features = ["query"] }
 http = { workspace = true }
+tonic = { workspace = true }

lib/saluki-api/src/lib.rs

@@ -2,6 +2,7 @@ pub use axum::response;
 pub use axum::routing;
 use axum::Router;
 pub use http::StatusCode;
+use tonic::service::Routes;
 
 pub mod extract {
     pub use axum::extract::*;
@@ -17,3 +18,100 @@ pub trait APIHandler {
     fn generate_initial_state(&self) -> Self::State;
     fn generate_routes(&self) -> Router<Self::State>;
 }
+
+/// API endpoint type.
+///
+/// Identifies whether or not a route should be exposed on the unprivileged or privileged API endpoint.
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub enum EndpointType {
+    /// The unprivileged (plain HTTP) API endpoint.
+    Unprivileged,
+
+    /// The privileged (TLS-protected) API endpoint.
+    Privileged,
+}
+
+impl EndpointType {
+    /// Returns a human-readable name for this endpoint type.
+    pub fn name(&self) -> &'static str {
+        match self {
+            Self::Unprivileged => "unprivileged",
+            Self::Privileged => "privileged",
+        }
+    }
+}
+
+/// API endpoint protocol.
+///
+/// Identifies which application protocol the route should be exposed to.
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub enum EndpointProtocol {
+    /// HTTP.
+    Http,
+
+    /// gRPC.
+    Grpc,
+}
+
+impl EndpointProtocol {
+    /// Returns a human-readable name for this endpoint protocol.
+    pub fn name(&self) -> &'static str {
+        match self {
+            Self::Http => "HTTP",
+            Self::Grpc => "gRPC",
+        }
+    }
+}
+
+/// A set of dynamic API routes.
+///
+/// Dynamic routes allow for processes to dynamically register/unregister themselves from running API endpoints,
+/// adapting to changes in the process state and without requiring all routes to be known and declared upfront.
+#[derive(Clone, Debug)]
+pub struct DynamicRoute {
+    /// Which API endpoint these routes target.
+    endpoint_type: EndpointType,
+
+    /// Which API protocol these routes target.
+    endpoint_protocol: EndpointProtocol,
+
+    /// The routes to serve.
+    router: Router<()>,
+}
+
+impl DynamicRoute {
+    /// Creates a dynamic HTTP route from the given API handler.
+    pub fn http<T: APIHandler>(endpoint_type: EndpointType, handler: T) -> Self {
+        let router = handler.generate_routes().with_state(handler.generate_initial_state());
+        Self::new(endpoint_type, EndpointProtocol::Http, router)
+    }
+
+    /// Creates a dynamic gRPC route from the given Tonic routes.
+    pub fn grpc(endpoint_type: EndpointType, routes: Routes) -> Self {
+        let router = routes.prepare().into_axum_router();
+        Self::new(endpoint_type, EndpointProtocol::Grpc, router)
+    }
+
+    fn new(endpoint_type: EndpointType, endpoint_protocol: EndpointProtocol, router: Router<()>) -> Self {
+        Self {
+            endpoint_type,
+            endpoint_protocol,
+            router,
+        }
+    }
+
+    /// Returns the type of endpoint these routes target.
+    pub fn endpoint_type(&self) -> EndpointType {
+        self.endpoint_type
+    }
+
+    /// Returns the protocol of endpoint these routes target.
+    pub fn endpoint_protocol(&self) -> EndpointProtocol {
+        self.endpoint_protocol
+    }
+
+    /// Consumes this route and returns the underlying router.
+    pub fn into_router(self) -> Router<()> {
+        self.router
+    }
+}

lib/saluki-app/Cargo.toml

@@ -12,11 +12,14 @@ workspace = true
 tls-fips = ["saluki-tls/fips"]
 
 [dependencies]
+arc-swap = { workspace = true }
+async-trait = { workspace = true }
 axum = { workspace = true }
 bytesize = { workspace = true }
 chrono = { workspace = true }
 chrono-tz = { workspace = true }
 http = { workspace = true }
+hyper = { workspace = true }
 iana-time-zone = { workspace = true }
 itoa = { workspace = true }
 memory-accounting = { workspace = true }