[V1] Simplify stats logging (#14082)

Signed-off-by: Nick Hill <nhill@redhat.com>

vllm/v1/engine/async_llm.py

 # SPDX-License-Identifier: Apache-2.0
 
 import asyncio
+import logging
 import os
 from collections.abc import AsyncGenerator, Mapping
 from typing import Optional, Union
@@ -57,10 +58,9 @@ class AsyncLLM(EngineClient):
         self.log_stats = log_stats
         self.stat_loggers: list[StatLoggerBase] = []
         if self.log_stats:
-            self.stat_loggers.extend([
-                LoggingStatLogger(),
-                PrometheusStatLogger(vllm_config),
-            ])
+            if logger.isEnabledFor(logging.INFO):
+                self.stat_loggers.append(LoggingStatLogger())
+            self.stat_loggers.append(PrometheusStatLogger(vllm_config))
 
         # Tokenizer (+ ensure liveness if running in another process).
         self.tokenizer = init_tokenizer_from_configs(
@@ -287,7 +287,7 @@ class AsyncLLM(EngineClient):
                 # 4) Logging.
                 # TODO(rob): make into a coroutine and launch it in
                 # background thread once Prometheus overhead is non-trivial.
-                self._log_stats(
+                self._record_stats(
                     scheduler_stats=outputs.scheduler_stats,
                     iteration_stats=iteration_stats,
                 )
@@ -306,7 +306,7 @@ class AsyncLLM(EngineClient):
         if self.log_requests:
             logger.info("Aborted request %s.", request_id)
 
-    def _log_stats(
+    def _record_stats(
         self,
         scheduler_stats: Optional[SchedulerStats],
         iteration_stats: Optional[IterationStats],
@@ -316,8 +316,8 @@ class AsyncLLM(EngineClient):
 
         assert scheduler_stats is not None
         assert iteration_stats is not None
-        for logger in self.stat_loggers:
-            logger.log(scheduler_stats=scheduler_stats,
+        for stat_logger in self.stat_loggers:
+            stat_logger.record(scheduler_stats=scheduler_stats,
                                iteration_stats=iteration_stats)
 
     def encode(
@@ -354,7 +354,8 @@ class AsyncLLM(EngineClient):
         scheduler_outputs=None,
         model_output=None,
     ) -> None:
-        logger.debug("Called do_log_stats.")
+        for stat_logger in self.stat_loggers:
+            stat_logger.log()
 
     async def check_health(self) -> None:
         logger.debug("Called check_health.")

vllm/v1/engine/core.py

@@ -316,19 +316,10 @@ class EngineCoreProc(EngineCore):
         # Loop until process is sent a SIGINT or SIGTERM
         while True:
             # 1) Poll the input queue until there is work to do.
-            if not self.scheduler.has_unfinished_requests():
-                while True:
-                    try:
-                        req = self.input_queue.get(timeout=POLLING_TIMEOUT_S)
-                        self._handle_client_request(*req)
-                        break
-                    except queue.Empty:
+            while not self.scheduler.has_unfinished_requests():
                 logger.debug("EngineCore busy loop waiting.")
-                        # Break out the loop so we can log_stats in step().
-                        if self.log_stats:
-                            break
-                    except BaseException:
-                        raise
+                req = self.input_queue.get()
+                self._handle_client_request(*req)
 
             # 2) Handle any new client requests.
             while not self.input_queue.empty():

vllm/v1/metrics/loggers.py

@@ -21,15 +21,19 @@ _LOCAL_LOGGING_INTERVAL_SEC = 5.0
 class StatLoggerBase(ABC):
 
     @abstractmethod
-    def log(self, scheduler_stats: SchedulerStats,
+    def record(self, scheduler_stats: SchedulerStats,
                iteration_stats: IterationStats):
         ...
 
+    def log(self):  # noqa
+        pass
+
 
 class LoggingStatLogger(StatLoggerBase):
 
     def __init__(self):
         self._reset(time.monotonic())
+        self.last_scheduler_stats = SchedulerStats()
 
     def _reset(self, now):
         self.last_log_time = now
@@ -41,11 +45,6 @@ class LoggingStatLogger(StatLoggerBase):
         # Prefix cache metrics. TODO: Make the interval configurable.
         self.prefix_caching_metrics = PrefixCachingMetrics()
 
-    def _local_interval_elapsed(self, now: float) -> bool:
-        # Log every _LOCAL_LOGGING_INTERVAL_SEC.
-        elapsed_time = now - self.last_log_time
-        return elapsed_time > _LOCAL_LOGGING_INTERVAL_SEC
-
     def _track_iteration_stats(self, iteration_stats: IterationStats):
         # Save tracked stats for token counters.
         self.num_prompt_tokens.append(iteration_stats.num_prompt_tokens)
@@ -56,7 +55,7 @@ class LoggingStatLogger(StatLoggerBase):
         # Compute summary metrics for tracked stats
         return float(np.sum(tracked_stats) / (now - self.last_log_time))
 
-    def log(self, scheduler_stats: SchedulerStats,
+    def record(self, scheduler_stats: SchedulerStats,
                iteration_stats: IterationStats):
         """Log Stats to standard output."""
 
@@ -64,16 +63,18 @@ class LoggingStatLogger(StatLoggerBase):
 
         self.prefix_caching_metrics.observe(scheduler_stats.prefix_cache_stats)
 
-        now = time.monotonic()
-        if not self._local_interval_elapsed(now):
-            return
+        self.last_scheduler_stats = scheduler_stats
 
+    def log(self):
+        now = time.monotonic()
         prompt_throughput = self._get_throughput(self.num_prompt_tokens, now)
         generation_throughput = self._get_throughput(
             self.num_generation_tokens, now)
 
         self._reset(now)
 
+        scheduler_stats = self.last_scheduler_stats
+
         # Format and print output.
         logger.info(
             "Avg prompt throughput: %.1f tokens/s, "
@@ -274,7 +275,7 @@ class PrometheusStatLogger(StatLoggerBase):
             labelnames=metrics_info.keys()).labels(**metrics_info)
         info_gauge.set(1)
 
-    def log(self, scheduler_stats: SchedulerStats,
+    def record(self, scheduler_stats: SchedulerStats,
                iteration_stats: IterationStats):
         """Log to prometheus."""
         self.gauge_scheduler_running.set(scheduler_stats.num_running_reqs)