feat(RateLimit): add Retry-After header for 429 errors

src/middleware/rate_limit.rs

@@ -6,7 +6,7 @@
 
 use std::{net::IpAddr, num::NonZeroU32, sync::Arc, time::Duration};
 
-use governor::{Quota, RateLimiter, clock::DefaultClock, state::keyed::DefaultKeyedStateStore};
+use governor::{Quota, RateLimiter, clock::{Clock, DefaultClock}, state::keyed::DefaultKeyedStateStore};
 use poem::{Endpoint, Error, IntoResponse, Middleware, Request, Response, Result};
 
 type BakitRateLimiter = RateLimiter<IpAddr, DefaultKeyedStateStore<IpAddr>, DefaultClock>;
@@ -104,20 +104,20 @@ impl<E: Endpoint> Endpoint for RateLimitEndpoint<E> {
         // Check rate limit
         let client_ip =
             Self::get_client_ip(&req).unwrap_or(IpAddr::V4(std::net::Ipv4Addr::UNSPECIFIED));
-        if self.limiter.check_key(&client_ip).is_err() {
-            let client_ip = Self::get_client_ip(&req)
-                .map_or_else(|| "unknown".to_string(), |ip| ip.to_string());
-
+        if let Err(negative) = self.limiter.check_key(&client_ip) {
             tracing::event!(
                 target: "backend::middleware::rate_limit",
                 tracing::Level::WARN,
                 client_ip = %client_ip,
                 "Rate limit exceeded"
             );
-
-            return Err(Error::from_status(
-                poem::http::StatusCode::TOO_MANY_REQUESTS,
-            ));
+            let clock = DefaultClock::default();
+            let wait = negative.wait_time_from(clock.now());
+            let response = Response::builder()
+                .status(poem::http::StatusCode::TOO_MANY_REQUESTS)
+                .header("Retry-After", wait.as_secs().to_string())
+                .finish();
+            return Err(Error::from_response(response));
         }
 
         // Process the request