collector: permit cross origin requests (#1398)

crates/ott-collector/src/cors.rs

@@ -0,0 +1,30 @@
+use rocket::fairing::{Fairing, Info, Kind};
+use rocket::http::Header;
+use rocket::response::status::NoContent;
+use rocket::{Request, Response};
+
+pub struct Cors;
+
+#[rocket::async_trait]
+impl Fairing for Cors {
+    fn info(&self) -> Info {
+        Info {
+            name: "Add CORS headers to responses",
+            kind: Kind::Response,
+        }
+    }
+
+    async fn on_response<'r>(&self, _request: &'r Request<'_>, response: &mut Response<'r>) {
+        response.set_header(Header::new("Access-Control-Allow-Origin", "*"));
+        response.set_header(Header::new("Access-Control-Allow-Methods", "*"));
+        response.set_header(Header::new("Access-Control-Allow-Headers", "*"));
+        response.set_header(Header::new("Access-Control-Expose-Headers", "*"));
+        response.set_header(Header::new("Access-Control-Allow-Credentials", "true"));
+        response.set_header(Header::new("Access-Control-Max-Age", "7200"));
+    }
+}
+
+#[options("/<_..>")]
+pub fn handle_preflight() -> NoContent {
+    NoContent
+}

crates/ott-collector/src/main.rs

@@ -1,6 +1,8 @@
 #[macro_use]
 extern crate rocket;
 
+mod cors;
+
 /// Serve the current system state
 #[get("/state")]
 fn serve_state() {
@@ -12,8 +14,8 @@ fn rocket() -> _ {
     // TODO: spawn discovery tokio task here
 
     rocket::build()
-        .mount("/", routes![status])
-        .mount("/", routes![serve_state])
+        .attach(cors::Cors)
+        .mount("/", routes![status, cors::handle_preflight, serve_state])
 }
 
 #[get("/status")]