[serve] collect request metrics at handles (ray-project#42578)

Collect request metrics for autoscaling at handles instead of replicas. This will allow queued metrics to be taken into account instead of just ongoing requests.

(3x) DeploymentHandle streaming throughput (ASYNC) (num_replicas=1, tokens_per_request=1000, batch_size=10)
| Collect on handles | Original |
| --- | --- |
| 12140.58 +- 431.94 tokens/s | 12365.42 +- 353.48 tokens/s |
| 12119.03 +- 255.58 tokens/s | 12395.43 +- 642.92 tokens/s |
| 12168.44 +- 653.06 tokens/s | 12365.76 +- 680.51 tokens/s |

(5x) HTTP streaming throughput (num_replicas=1, tokens_per_request=1000, batch_size=10, use_intermediate_deployment=False)
| Collect on handles | Original |
| --- | --- |
| 141118.93 +- 103940.74 tokens/s | 143454.65 +- 103615.47 tokens/s |
| 225063.66 +- 5347.35 tokens/s | 228244.37 +- 6209.89 tokens/s |
| 225684.1 +- 3262.97 tokens/s | 221354.73 +- 2928.82 tokens/s |
| 220755.65 +- 6837.1 tokens/s | 188224.32 +- 78546.09 tokens/s |
| 221404.26 +- 3427.73 tokens/s | 223172.25 +- 4064.79 tokens/s |

(4x) DeploymentHandle throughput (num_replicas=1, batch_size=100)
| Collect on handles | Original |
| --- | --- |
| 1766.19 +- 15.25 requests/s | 1819.54 +- 5.26 requests/s |
| 1760.92 +- 51.87 requests/s | 1762.08 +- 21.04 requests/s |
| 1796.22 +- 10.52 requests/s | 1750.08 +- 31.73 requests/s |
| 1788.1 +- 29.98 requests/s | 1779.63 +- 24.86 requests/s |


Signed-off-by: Cindy Zhang <cindyzyx9@gmail.com>
Streaming HTTP throughput

python/ray/serve/_private/constants.py

@@ -268,3 +268,9 @@
 
 # The default autoscaling policy to use if none is specified.
 DEFAULT_AUTOSCALING_POLICY = "ray.serve.autoscaling_policy:default_autoscaling_policy"
+
+# Feature flag to enable collecting all queued and ongoing request
+# metrics at handles instead of replicas. OFF by default.
+RAY_SERVE_COLLECT_AUTOSCALING_METRICS_ON_HANDLE = (
+    os.environ.get("RAY_SERVE_COLLECT_AUTOSCALING_METRICS_ON_HANDLE", "0") == "1"
+)

python/ray/serve/_private/controller.py

@@ -260,7 +260,7 @@ def record_autoscaling_metrics(self, data: Dict[str, float], send_timestamp: flo
         )
         self.deployment_state_manager.record_autoscaling_metrics(data, send_timestamp)
 
-    def record_handle_metrics(self, data: Dict[str, float], send_timestamp: float):
+    def record_handle_metrics(self, data, send_timestamp: float):
         logger.debug(f"Received handle metrics: {data} at timestamp {send_timestamp}")
         self.deployment_state_manager.record_handle_metrics(data, send_timestamp)
 

python/ray/serve/_private/deployment_state.py

@@ -35,6 +35,7 @@
 from ray.serve._private.config import DeploymentConfig
 from ray.serve._private.constants import (
     MAX_DEPLOYMENT_CONSTRUCTOR_RETRY_COUNT,
+    RAY_SERVE_COLLECT_AUTOSCALING_METRICS_ON_HANDLE,
     RAY_SERVE_FORCE_STOP_UNHEALTHY_REPLICAS,
     REPLICA_HEALTH_CHECK_UNHEALTHY_THRESHOLD,
     SERVE_LOGGER_NAME,
@@ -187,6 +188,13 @@ class DeploymentStateUpdateResult:
 _SCALING_LOG_ENABLED = os.environ.get("SERVE_ENABLE_SCALING_LOG", "0") != "0"
 
 
+@dataclass
+class HandleRequestMetric:
+    queued_requests: float
+    running_requests: Dict[str, float]
+    timestamp: float
+
+
 def print_verbose_scaling_log():
     assert _SCALING_LOG_ENABLED
 
@@ -1246,7 +1254,9 @@ def __init__(
         self.replica_average_ongoing_requests: Dict[str, float] = dict()
 
         # Map from handle ID to (# requests recorded at handle, recording timestamp)
-        self.handle_requests: Dict[str, Tuple(float, float)] = dict()
+        self.handle_requests: Dict[str, HandleRequestMetric] = dict()
+        self.requests_queued_at_handles: Dict[str, float] = dict()
+        # Number of ongoing requests reported by replicas
         self.replica_average_ongoing_requests: Dict[str, float] = dict()
 
         self.health_check_gauge = metrics.Gauge(
@@ -1586,23 +1596,37 @@ def deploy(self, deployment_info: DeploymentInfo) -> bool:
         self._backoff_time_s = 1
         return True
 
-    def get_total_num_requests(self) -> int:
-        """Return total number of ongoing requests in Serve.
+    def get_total_num_requests(self) -> float:
+        """Get average total number of requests aggregated over the past
+        `look_back_period_s` number of seconds.
 
         If there are 0 running replicas, then returns the total number
-        of requests queued at handles.
+        of requests queued at handles
+
+        If the flag RAY_SERVE_COLLECT_AUTOSCALING_METRICS_ON_HANDLE is
+        set to 1, the returned average includes both queued and ongoing
+        requests. Otherwise, the returned average includes only ongoing
+        requests.
         """
 
         total_requests = 0
         running_replicas = self._replicas.get([ReplicaState.RUNNING])
-        for replica in running_replicas:
-            replica_tag = replica.replica_tag
-            if replica_tag in self.replica_average_ongoing_requests:
-                total_requests += self.replica_average_ongoing_requests[replica_tag][1]
 
-        if len(running_replicas) == 0:
-            for handle_metrics in self.handle_requests.values():
-                total_requests += handle_metrics[1]
+        if (
+            RAY_SERVE_COLLECT_AUTOSCALING_METRICS_ON_HANDLE
+            or len(running_replicas) == 0
+        ):
+            for handle_metric in self.handle_requests.values():
+                total_requests += handle_metric.queued_requests
+                for replica in running_replicas:
+                    id = replica.replica_tag
+                    if id in handle_metric.running_requests:
+                        total_requests += handle_metric.running_requests[id]
+        else:
+            for replica in running_replicas:
+                id = replica.replica_tag
+                if id in self.replica_average_ongoing_requests:
+                    total_requests += self.replica_average_ongoing_requests[id][1]
 
         return total_requests
 
@@ -1613,11 +1637,12 @@ def autoscale(self) -> int:
             return
 
         total_num_requests = self.get_total_num_requests()
+        num_running_replicas = len(self.get_running_replica_infos())
         autoscaling_policy_manager = self.autoscaling_policy_manager
         decision_num_replicas = autoscaling_policy_manager.get_decision_num_replicas(
             curr_target_num_replicas=self._target_state.target_num_replicas,
             total_num_requests=total_num_requests,
-            num_running_replicas=len(self.get_running_replica_infos()),
+            num_running_replicas=num_running_replicas,
             target_capacity=self._target_state.info.target_capacity,
             target_capacity_direction=self._target_state.info.target_capacity_direction,
         )
@@ -1631,7 +1656,8 @@ def autoscale(self) -> int:
         logger.info(
             f"Autoscaling replicas for deployment '{self.deployment_name}' in "
             f"application '{self.app_name}' to {decision_num_replicas}. "
-            f"Current number of requests: {total_num_requests}."
+            f"Current number of requests: {total_num_requests}. Current number of "
+            f"running replicas: {num_running_replicas}."
         )
 
         new_info = copy(self._target_state.info)
@@ -2279,15 +2305,23 @@ def record_autoscaling_metrics(
             )
 
     def record_request_metrics_for_handle(
-        self, handle_id: str, num_requests: float, send_timestamp: float
+        self,
+        handle_id: str,
+        queued_requests: float,
+        running_requests: Dict[str, float],
+        send_timestamp: float,
     ) -> None:
         """Update request metric for a specific handle."""
 
         if (
             handle_id not in self.handle_requests
-            or send_timestamp > self.handle_requests[handle_id][0]
+            or send_timestamp > self.handle_requests[handle_id].timestamp
         ):
-            self.handle_requests[handle_id] = (send_timestamp, num_requests)
+            self.handle_requests[handle_id] = HandleRequestMetric(
+                queued_requests=queued_requests,
+                running_requests=running_requests,
+                timestamp=send_timestamp,
+            )
 
     def record_multiplexed_model_ids(
         self, replica_name: str, multiplexed_model_ids: List[str]
@@ -2367,18 +2401,14 @@ def record_autoscaling_metrics(self, data, send_timestamp: float):
                 replica_name.deployment_id
             ].record_autoscaling_metrics(replica_tag, window_avg, send_timestamp)
 
-    def record_handle_metrics(self, data: Dict[str, float], send_timestamp: float):
-        id, num_requests = data
-        if num_requests is not None:
-            deployment_id, handle_id = id
-            # There can be handles to deleted deployments still sending
-            # metrics to the controller
-            if deployment_id in self._deployment_states:
-                self._deployment_states[
-                    deployment_id
-                ].record_request_metrics_for_handle(
-                    handle_id, num_requests, send_timestamp
-                )
+    def record_handle_metrics(self, data, send_timestamp: float):
+        deployment_id, handle_id, queued_requests, running_requests = data
+        # NOTE(zcin): There can be handles to deleted deployments still
+        # sending metrics to the controller
+        if deployment_id in self._deployment_states:
+            self._deployment_states[deployment_id].record_request_metrics_for_handle(
+                handle_id, queued_requests, running_requests, send_timestamp
+            )
 
     def get_autoscaling_metrics(self):
         """Return autoscaling metrics (used for dumping from controller)"""

python/ray/serve/_private/replica.py

@@ -33,6 +33,7 @@
     DEFAULT_LATENCY_BUCKET_MS,
     GRPC_CONTEXT_ARG_NAME,
     HEALTH_CHECK_METHOD,
+    RAY_SERVE_COLLECT_AUTOSCALING_METRICS_ON_HANDLE,
     RAY_SERVE_GAUGE_METRIC_SET_PERIOD_S,
     RAY_SERVE_REPLICA_AUTOSCALING_METRIC_RECORD_PERIOD_S,
     RECONFIGURE_METHOD,
@@ -180,7 +181,10 @@ def set_autoscaling_config(self, autoscaling_config: Optional[AutoscalingConfig]
 
         self._autoscaling_config = autoscaling_config
 
-        if self._autoscaling_config:
+        if (
+            not RAY_SERVE_COLLECT_AUTOSCALING_METRICS_ON_HANDLE
+            and self._autoscaling_config
+        ):
             # Push autoscaling metrics to the controller periodically.
             self._metrics_pusher.register_or_update_task(
                 self.PUSH_METRICS_TO_CONTROLLER_TASK_NAME,

python/ray/serve/_private/replica_scheduler/pow_2_scheduler.py

@@ -6,7 +6,17 @@
 import time
 from collections import defaultdict, deque
 from dataclasses import dataclass
-from typing import AsyncGenerator, DefaultDict, Deque, Dict, List, Optional, Set, Union
+from typing import (
+    AsyncGenerator,
+    DefaultDict,
+    Deque,
+    Dict,
+    List,
+    Optional,
+    Set,
+    Tuple,
+    Union,
+)
 
 import ray
 from ray.exceptions import RayActorError
@@ -657,11 +667,11 @@ async def choose_replica_for_query(self, query: Query) -> ReplicaWrapper:
 
     async def assign_replica(
         self, query: Query
-    ) -> Union[ray.ObjectRef, "ray._raylet.ObjectRefGenerator"]:
+    ) -> Tuple[Union[ray.ObjectRef, "ray._raylet.ObjectRefGenerator"], str]:
         """Choose a replica for the request and send it.
 
         This will block indefinitely if no replicas are available to handle the
         request, so it's up to the caller to time out or cancel the request.
         """
         replica = await self.choose_replica_for_query(query)
-        return replica.send_query(query)
+        return replica.send_query(query), replica.replica_id