feat: return 429 if request queue full

runtime/src/global_request_scheduler.c

@@ -43,6 +43,7 @@ global_request_scheduler_initialize(struct global_request_scheduler_config *conf
 /**
  * Adds a sandbox to the request scheduler
  * @param sandbox
+ * @returns pointer to sandbox if added. NULL otherwise
  */
 struct sandbox *
 global_request_scheduler_add(struct sandbox *sandbox)

runtime/src/global_request_scheduler_deque.c

@@ -12,7 +12,7 @@ static pthread_mutex_t global_request_scheduler_deque_mutex = PTHREAD_MUTEX_INIT
 /**
  * Pushes a sandbox to the global deque
  * @param sandbox_raw
- * @returns pointer to request if added. NULL otherwise
+ * @returns pointer to sandbox if added. NULL otherwise
  */
 static struct sandbox *
 global_request_scheduler_deque_add(struct sandbox *sandbox)

runtime/src/global_request_scheduler_minheap.c

@@ -12,7 +12,7 @@ static struct priority_queue *global_request_scheduler_minheap;
 /**
  * Pushes a sandbox to the global deque
  * @param sandbox
- * @returns pointer to request if added. Panics runtime otherwise
+ * @returns pointer to sandbox if added. NULL otherwise
  */
 static struct sandbox *
 global_request_scheduler_minheap_add(struct sandbox *sandbox)
@@ -22,8 +22,8 @@ global_request_scheduler_minheap_add(struct sandbox *sandbox)
 	if (unlikely(!listener_thread_is_running())) panic("%s is only callable by the listener thread\n", __func__);
 
 	int return_code = priority_queue_enqueue(global_request_scheduler_minheap, sandbox);
-	/* TODO: Propagate -1 to caller. Issue #91 */
-	if (return_code == -ENOSPC) panic("Request Queue is full\n");
+
+	if (return_code != 0) return NULL;
 	return sandbox;
 }
 

runtime/src/listener_thread.c

@@ -189,8 +189,14 @@ listener_thread_main(void *dummy)
 					                    &sandbox->client_address);
 				}
 
-				/* Add to the Global Sandbox Request Scheduler */
-				global_request_scheduler_add(sandbox);
+				/* If the global request scheduler is full, return a 429 to the client */
+				sandbox = global_request_scheduler_add(sandbox);
+				if (unlikely(sandbox == NULL)) {
+					client_socket_send_oneshot(sandbox->client_socket_descriptor,
+					                           http_header_build(429), http_header_len(429));
+					client_socket_close(sandbox->client_socket_descriptor,
+					                    &sandbox->client_address);
+				}
 
 			} /* while true */
 		}         /* for loop */