[Serve] Skip routing stats collection for deployments without record_routing_stats

python/ray/serve/_private/deployment_state.py

@@ -341,6 +341,7 @@ def __init__(
         self._routing_stats: Dict[str, Any] = {}
         self._record_routing_stats_ref: Optional[ObjectRef] = None
         self._last_record_routing_stats_time: float = 0.0
+        self._has_user_routing_stats_method: bool = False
         self._ingress: bool = False
 
         # Outbound deployments polling state
@@ -914,6 +915,7 @@ def check_ready(self) -> Tuple[ReplicaStartupStatus, Optional[str]]:
                         self._rank,
                         self._route_patterns,
                         self._outbound_deployments,
+                        self._has_user_routing_stats_method,
                     ) = ray.get(self._ready_obj_ref)
             except RayTaskError as e:
                 logger.exception(
@@ -1075,14 +1077,22 @@ def _should_record_routing_stats(self) -> bool:
         """Determines if a new record routing stats should be kicked off.
 
         A record routing stats will be started if:
-            1) There is not already an active record routing stats.
-            2) It has been more than request_routing_stats_period_s since
+            1) The user has defined a record_routing_stats method on their
+               deployment class. If not, skip entirely to avoid unnecessary
+               remote calls that would just return empty dicts.
+            2) There is not already an active record routing stats.
+            3) It has been more than request_routing_stats_period_s since
                the previous record routing stats was *started*.
 
         This assumes that self._record_routing_stats_ref is reset to `None`
         when an active record routing stats succeeds or fails (due to
         returning or timeout).
         """
+        if not self._has_user_routing_stats_method:
+            # The user hasn't defined a record_routing_stats method, so
+            # there's no point in making remote calls to collect stats.
+            return False
+
         if self._record_routing_stats_ref is not None:
             # There's already an active record routing stats.
             return False

python/ray/serve/_private/replica.py

@@ -260,6 +260,7 @@ async def gen_wrapper(
     ReplicaRank,  # rank
     Optional[List[str]],  # route_patterns
     Optional[List[DeploymentID]],  # outbound_deployments
+    bool,  # has_user_routing_stats_method
 ]
 
 
@@ -1073,6 +1074,11 @@ def get_metadata(self) -> ReplicaMetadata:
             if hasattr(self._user_callable_asgi_app, "routes"):
                 route_patterns = extract_route_patterns(self._user_callable_asgi_app)
 
+        has_user_routing_stats_method = (
+            self._user_callable_wrapper is not None
+            and self._user_callable_wrapper.has_user_routing_stats_method
+        )
+
         return (
             self._version.deployment_config,
             self._version,
@@ -1084,6 +1090,7 @@ def get_metadata(self) -> ReplicaMetadata:
             current_rank,
             route_patterns,
             self.list_outbound_deployments(),
+            has_user_routing_stats_method,
         )
 
     def get_dynamically_created_handles(self) -> Set[DeploymentID]:
@@ -3019,6 +3026,11 @@ def call_user_health_check(self) -> Optional[concurrent.futures.Future]:
 
         return None
 
+    @property
+    def has_user_routing_stats_method(self) -> bool:
+        """Whether the user has defined a record_routing_stats method."""
+        return self._user_record_routing_stats is not None
+
     def call_user_record_routing_stats(self) -> Optional[concurrent.futures.Future]:
         self._raise_if_not_initialized("call_user_record_routing_stats")
 

python/ray/serve/tests/test_controller_recovery.py

@@ -65,7 +65,7 @@ def __call__(self, *args):
     replica_version_hash = None
     for replica in deployment_dict[id]:
         ref = replica.get_actor_handle().initialize_and_get_metadata.remote()
-        _, version, _, _, _, _, _, _, _, _ = ray.get(ref)
+        _, version, _, _, _, _, _, _, _, _, _ = ray.get(ref)
         if replica_version_hash is None:
             replica_version_hash = hash(version)
         assert replica_version_hash == hash(version), (
@@ -118,7 +118,7 @@ def __call__(self, *args):
     for replica_name in recovered_replica_names:
         actor_handle = ray.get_actor(replica_name, namespace=SERVE_NAMESPACE)
         ref = actor_handle.initialize_and_get_metadata.remote()
-        _, version, _, _, _, _, _, _, _, _ = ray.get(ref)
+        _, version, _, _, _, _, _, _, _, _, _ = ray.get(ref)
         assert replica_version_hash == hash(
             version
         ), "Replica version hash should be the same after recover from actor names"

python/ray/serve/tests/test_metrics.py

@@ -1221,6 +1221,9 @@ class Model:
         def __call__(self):
             return "hello"
 
+        async def record_routing_stats(self):
+            return {}
+
     serve.run(Model.bind(), name="app")
     timeseries = PrometheusTimeseries()