[CI] Restore SMG e2e on 2-gpu-h100 / 4-gpu-h100 runners (#24222)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

python/sglang/srt/entrypoints/grpc_server.py

@@ -10,6 +10,7 @@ once the gRPC request manager is ready, regardless of whether --enable-metrics
 is set.
 """
 
+import inspect
 import json
 import logging
 import time
@@ -220,12 +221,37 @@ async def serve_grpc(server_args, model_info=None):
                 exc_info=True,
             )
 
-    try:
-        await _serve_grpc(
-            server_args,
-            model_info,
-            on_request_manager_ready=_on_request_manager_ready,
+    # Older smg-grpc-servicer releases (≤ 0.5.2) accept only (server_args,
+    # model_info) and reject the on_request_manager_ready hook. The hook is
+    # what calls _start_sidecar_server, so dropping the kwarg disables the
+    # entire HTTP sidecar (Prometheus /metrics and /start_profile +
+    # /stop_profile). Core gRPC serving still works without it.
+    serve_kwargs: dict = {}
+    sidecar_supported = (
+        "on_request_manager_ready" in inspect.signature(_serve_grpc).parameters
+    )
+    if sidecar_supported:
+        serve_kwargs["on_request_manager_ready"] = _on_request_manager_ready
+    elif server_args.enable_metrics:
+        # User explicitly asked for metrics but the installed servicer can't
+        # start the sidecar that serves them — fail loud rather than silently
+        # produce a server with no /metrics endpoint.
+        raise RuntimeError(
+            "--enable-metrics requires smg-grpc-servicer ≥ 0.5.3 (the version "
+            "that accepts 'on_request_manager_ready'); installed version "
+            "lacks the hook so the HTTP sidecar would never start. Upgrade "
+            "smg-grpc-servicer or remove --enable-metrics."
         )
+    else:
+        logger.warning(
+            "Installed smg-grpc-servicer does not accept "
+            "'on_request_manager_ready'; HTTP sidecar disabled "
+            "(no /metrics, /start_profile, /stop_profile). "
+            "Upgrade smg-grpc-servicer to ≥ 0.5.3 to enable it."
+        )
+
+    try:
+        await _serve_grpc(server_args, model_info, **serve_kwargs)
     finally:
         if sidecar_runner is not None:
             try: