Support HTTP response status code prometheus metrics (#14710)

python/sglang/srt/entrypoints/http_server.py

@@ -122,6 +122,7 @@ from sglang.srt.server_args import PortArgs, ServerArgs
 from sglang.srt.utils import (
     add_api_key_middleware,
     add_prometheus_middleware,
+    add_prometheus_track_response_middleware,
     delete_directory,
     get_bool_env_var,
     kill_process_tree,
@@ -1397,6 +1398,9 @@ def launch_server(
         )
     )
 
+    if server_args.enable_metrics:
+        add_prometheus_track_response_middleware(app)
+
     # Pass additional arguments to the lifespan function.
     # They will be used for additional initialization setups.
     if server_args.tokenizer_worker_num == 1:

python/sglang/srt/utils/common.py

@@ -1502,6 +1502,31 @@ def add_prometheus_middleware(app):
     app.routes.append(metrics_route)
 
 
+def add_prometheus_track_response_middleware(app):
+    from prometheus_client import Counter
+
+    http_response_status_counter = Counter(
+        name="sglang:http_responses_total",
+        documentation="Total number of HTTP responses by endpoint and status code",
+        labelnames=["endpoint", "status_code", "method"],
+    )
+
+    @app.middleware("http")
+    async def track_http_status_code(request, call_next):
+        response = await call_next(request)
+
+        route = request.scope.get("route")
+        endpoint = route.path if route else "Unknown"
+
+        http_response_status_counter.labels(
+            endpoint=endpoint,
+            status_code=str(response.status_code),
+            method=request.method,
+        ).inc()
+
+        return response
+
+
 def bind_port(port):
     """Bind to a specific port, assuming it's available."""
     sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)