BREAKING CHANGE(ts-api,rustproxy): remove deprecated TypeScript protocol and utility exports while hardening QUIC, HTTP/3, WebSocket, and rate limiter cleanup paths

rust/crates/rustproxy-metrics/src/collector.rs

@@ -411,11 +411,24 @@ impl MetricsCollector {
     }
 
     /// Record a backend connection closing.
+    /// Removes all per-backend tracking entries when the active count reaches 0.
     pub fn backend_connection_closed(&self, key: &str) {
         if let Some(counter) = self.backend_active.get(key) {
-            let val = counter.load(Ordering::Relaxed);
-            if val > 0 {
-                counter.fetch_sub(1, Ordering::Relaxed);
+            let prev = counter.fetch_sub(1, Ordering::Relaxed);
+            if prev <= 1 {
+                // Active count reached 0 — clean up all per-backend maps
+                drop(counter); // release DashMap ref before remove
+                self.backend_active.remove(key);
+                self.backend_total.remove(key);
+                self.backend_protocol.remove(key);
+                self.backend_connect_errors.remove(key);
+                self.backend_handshake_errors.remove(key);
+                self.backend_request_errors.remove(key);
+                self.backend_connect_time_us.remove(key);
+                self.backend_connect_count.remove(key);
+                self.backend_pool_hits.remove(key);
+                self.backend_pool_misses.remove(key);
+                self.backend_h2_failures.remove(key);
             }
         }
     }
@@ -1213,10 +1226,13 @@ mod tests {
         // No entry created
         assert!(collector.backend_active.get(key).is_none());
 
-        // Open one, close two — should saturate at 0
+        // Open one, close — entries are removed when active count reaches 0
         collector.backend_connection_opened(key, Duration::from_millis(1));
         collector.backend_connection_closed(key);
+        // Entry should be cleaned up (active reached 0)
+        assert!(collector.backend_active.get(key).is_none());
+        // Second close on missing entry is a no-op
         collector.backend_connection_closed(key);
-        assert_eq!(collector.backend_active.get(key).unwrap().load(Ordering::Relaxed), 0);
+        assert!(collector.backend_active.get(key).is_none());
     }
 }