[V1][Metrics] Allow V1 AsyncLLM to use custom logger

tests/v1/engine/test_async_llm.py

@@ -3,16 +3,19 @@
 import asyncio
 from contextlib import ExitStack
 from typing import Optional
+from unittest.mock import MagicMock
 
 import pytest
 
 from vllm import SamplingParams
 from vllm.assets.image import ImageAsset
+from vllm.config import VllmConfig
 from vllm.engine.arg_utils import AsyncEngineArgs
 from vllm.inputs import PromptType
 from vllm.platforms import current_platform
 from vllm.sampling_params import RequestOutputKind
 from vllm.v1.engine.async_llm import AsyncLLM
+from vllm.v1.metrics.loggers import LoggingStatLogger
 
 if not current_platform.is_cuda():
     pytest.skip(reason="V1 currently only supported on CUDA.",
@@ -216,3 +219,33 @@ async def test_finished_flag(monkeypatch: pytest.MonkeyPatch, n: int,
         # Assert only the last output has the finished flag set
         assert all(not out.finished for out in outputs[:-1])
         assert outputs[-1].finished
+
+
+class MockLoggingStatLogger(LoggingStatLogger):
+
+    def __init__(self, vllm_config: VllmConfig, engine_index: int = 0):
+        super().__init__(vllm_config, engine_index)
+        self.log = MagicMock()
+
+
+@pytest.mark.asyncio
+async def test_customize_loggers(monkeypatch):
+    """Test that we can customize the loggers.
+    If a customized logger is provided at the init, it should
+    be used directly.
+    """
+
+    with monkeypatch.context() as m, ExitStack() as after:
+        m.setenv("VLLM_USE_V1", "1")
+
+        engine = AsyncLLM.from_engine_args(
+            TEXT_ENGINE_ARGS,
+            stat_loggers=[MockLoggingStatLogger],
+        )
+        after.callback(engine.shutdown)
+
+        await engine.do_log_stats()
+
+        assert len(engine.stat_loggers) == 1
+        assert len(engine.stat_loggers[0]) == 1
+        engine.stat_loggers[0][0].log.assert_called_once()

vllm/v1/engine/async_llm.py

@@ -1,6 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
 import asyncio
-import logging
 from collections.abc import AsyncGenerator, Mapping
 from copy import copy
 from typing import Optional, Union
@@ -33,8 +32,8 @@
 from vllm.v1.engine.parallel_sampling import ParentRequest
 from vllm.v1.engine.processor import Processor
 from vllm.v1.executor.abstract import Executor
-from vllm.v1.metrics.loggers import (LoggingStatLogger, PrometheusStatLogger,
-                                     StatLoggerBase)
+from vllm.v1.metrics.loggers import (StatLoggerBase, StatLoggerFactory,
+                                     setup_default_loggers)
 from vllm.v1.metrics.stats import IterationStats, SchedulerStats
 
 logger = init_logger(__name__)
@@ -52,7 +51,28 @@ def __init__(
         use_cached_outputs: bool = False,
         log_requests: bool = True,
         start_engine_loop: bool = True,
+        stat_loggers: Optional[list[StatLoggerFactory]] = None,
     ) -> None:
+        """
+        Create an AsyncLLM.
+
+        Args:
+            vllm_config: global configuration.
+            executor_class: an Executor impl, e.g. MultiprocExecutor.
+            log_stats: Whether to log stats.
+            usage_context: Usage context of the LLM.
+            mm_registry: Multi-modal registry.
+            use_cached_outputs: Whether to use cached outputs.
+            log_requests: Whether to log requests.
+            start_engine_loop: Whether to start the engine loop.
+            stat_loggers: customized stat loggers for the engine.
+                If not provided, default stat loggers will be used.
+                PLEASE BE AWARE THAT STAT LOGGER IS NOT STABLE
+                IN V1, AND ITS BASE CLASS INTERFACE MIGHT CHANGE.
+
+        Returns:
+            None
+        """
         if not envs.VLLM_USE_V1:
             raise ValueError(
                 "Using V1 AsyncLLMEngine, but envs.VLLM_USE_V1=False. "
@@ -66,15 +86,12 @@ def __init__(
         self.log_stats = log_stats
 
         # Set up stat loggers; independent set for each DP rank.
-        self.stat_loggers: list[list[StatLoggerBase]] = []
-        if self.log_stats:
-            for i in range(vllm_config.parallel_config.data_parallel_size):
-                loggers: list[StatLoggerBase] = []
-                if logger.isEnabledFor(logging.INFO):
-                    loggers.append(LoggingStatLogger(engine_index=i))
-                loggers.append(
-                    PrometheusStatLogger(vllm_config, engine_index=i))
-                self.stat_loggers.append(loggers)
+        self.stat_loggers: list[list[StatLoggerBase]] = setup_default_loggers(
+            vllm_config=vllm_config,
+            log_stats=self.log_stats,
+            engine_num=vllm_config.parallel_config.data_parallel_size,
+            custom_stat_loggers=stat_loggers,
+        )
 
         # Tokenizer (+ ensure liveness if running in another process).
         self.tokenizer = init_tokenizer_from_configs(
@@ -118,7 +135,7 @@ def from_vllm_config(
         vllm_config: VllmConfig,
         start_engine_loop: bool = True,
         usage_context: UsageContext = UsageContext.ENGINE_CONTEXT,
-        stat_loggers: Optional[dict[str, StatLoggerBase]] = None,
+        stat_loggers: Optional[list[StatLoggerFactory]] = None,
         disable_log_requests: bool = False,
         disable_log_stats: bool = False,
     ) -> "AsyncLLM":
@@ -129,17 +146,12 @@ def from_vllm_config(
                 "AsyncLLMEngine.from_vllm_config(...) or explicitly set "
                 "VLLM_USE_V1=0 or 1 and report this issue on Github.")
 
-        # FIXME(rob): refactor VllmConfig to include the StatLoggers
-        # include StatLogger in the Oracle decision.
-        if stat_loggers is not None:
-            raise ValueError("Custom StatLoggers are not yet supported on V1. "
-                             "Explicitly set VLLM_USE_V1=0 to disable V1.")
-
         # Create the LLMEngine.
         return cls(
             vllm_config=vllm_config,
             executor_class=Executor.get_class(vllm_config),
             start_engine_loop=start_engine_loop,
+            stat_loggers=stat_loggers,
             log_requests=not disable_log_requests,
             log_stats=not disable_log_stats,
             usage_context=usage_context,
@@ -151,6 +163,7 @@ def from_engine_args(
         engine_args: AsyncEngineArgs,
         start_engine_loop: bool = True,
         usage_context: UsageContext = UsageContext.ENGINE_CONTEXT,
+        stat_loggers: Optional[list[StatLoggerFactory]] = None,
     ) -> "AsyncLLM":
         """Create an AsyncLLM from the EngineArgs."""
 
@@ -166,6 +179,7 @@ def from_engine_args(
             log_stats=not engine_args.disable_log_stats,
             start_engine_loop=start_engine_loop,
             usage_context=usage_context,
+            stat_loggers=stat_loggers,
         )
 
     def __del__(self):

vllm/v1/engine/llm_engine.py

@@ -10,7 +10,6 @@
 from vllm.config import ParallelConfig, VllmConfig
 from vllm.distributed import stateless_destroy_torch_distributed_process_group
 from vllm.engine.arg_utils import EngineArgs
-from vllm.engine.metrics_types import StatLoggerBase
 from vllm.inputs import PromptType
 from vllm.logger import init_logger
 from vllm.lora.request import LoRARequest
@@ -28,6 +27,7 @@
 from vllm.v1.engine.parallel_sampling import ParentRequest
 from vllm.v1.engine.processor import Processor
 from vllm.v1.executor.abstract import Executor
+from vllm.v1.metrics.loggers import StatLoggerFactory
 
 logger = init_logger(__name__)
 
@@ -43,7 +43,7 @@ def __init__(
         executor_class: type[Executor],
         log_stats: bool,
         usage_context: UsageContext = UsageContext.ENGINE_CONTEXT,
-        stat_loggers: Optional[dict[str, StatLoggerBase]] = None,
+        stat_loggers: Optional[list[StatLoggerFactory]] = None,
         mm_registry: MultiModalRegistry = MULTIMODAL_REGISTRY,
         use_cached_outputs: bool = False,
         multiprocess_mode: bool = False,
@@ -55,6 +55,11 @@ def __init__(
                 "LLMEngine.from_vllm_config(...) or explicitly set "
                 "VLLM_USE_V1=0 or 1 and report this issue on Github.")
 
+        if stat_loggers is not None:
+            raise NotImplementedError(
+                "Passing StatLoggers to LLMEngine in V1 is not yet supported. "
+                "Set VLLM_USE_V1=0 and file and issue on Github.")
+
         self.vllm_config = vllm_config
         self.model_config = vllm_config.model_config
         self.cache_config = vllm_config.cache_config
@@ -101,14 +106,9 @@ def from_vllm_config(
         cls,
         vllm_config: VllmConfig,
         usage_context: UsageContext = UsageContext.ENGINE_CONTEXT,
-        stat_loggers: Optional[dict[str, StatLoggerBase]] = None,
+        stat_loggers: Optional[list[StatLoggerFactory]] = None,
         disable_log_stats: bool = False,
     ) -> "LLMEngine":
-        if stat_loggers is not None:
-            raise NotImplementedError(
-                "Passing StatLoggers to V1 is not yet supported. "
-                "Set VLLM_USE_V1=0 and file and issue on Github.")
-
         return cls(vllm_config=vllm_config,
                    executor_class=Executor.get_class(vllm_config),
                    log_stats=(not disable_log_stats),
@@ -121,7 +121,7 @@ def from_engine_args(
         cls,
         engine_args: EngineArgs,
         usage_context: UsageContext = UsageContext.ENGINE_CONTEXT,
-        stat_loggers: Optional[dict[str, StatLoggerBase]] = None,
+        stat_loggers: Optional[list[StatLoggerFactory]] = None,
         enable_multiprocessing: bool = False,
     ) -> "LLMEngine":
         """Creates an LLM engine from the engine arguments."""

vllm/v1/metrics/loggers.py

@@ -1,8 +1,9 @@
 # SPDX-License-Identifier: Apache-2.0
 
+import logging
 import time
 from abc import ABC, abstractmethod
-from typing import Optional
+from typing import Callable, Optional
 
 import numpy as np
 import prometheus_client
@@ -18,8 +19,20 @@
 
 _LOCAL_LOGGING_INTERVAL_SEC = 5.0
 
+StatLoggerFactory = Callable[[VllmConfig, int], "StatLoggerBase"]
+
 
 class StatLoggerBase(ABC):
+    """Interface for logging metrics.
+
+    API users may define custom loggers that implement this interface.
+    However, note that the `SchedulerStats` and `IterationStats` classes
+    are not considered stable interfaces and may change in future versions.
+    """
+
+    @abstractmethod
+    def __init__(self, vllm_config: VllmConfig, engine_index: int = 0):
+        ...
 
     @abstractmethod
     def record(self, scheduler_stats: SchedulerStats,
@@ -32,7 +45,7 @@ def log(self):  # noqa
 
 class LoggingStatLogger(StatLoggerBase):
 
-    def __init__(self, engine_index: int = 0):
+    def __init__(self, vllm_config: VllmConfig, engine_index: int = 0):
         self.engine_index = engine_index
         self._reset(time.monotonic())
         self.last_scheduler_stats = SchedulerStats()
@@ -462,3 +475,31 @@ def build_cudagraph_buckets(vllm_config: VllmConfig) -> list[int]:
         return buckets
     else:
         return [1, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8096]
+
+
+def setup_default_loggers(
+    vllm_config: VllmConfig,
+    log_stats: bool,
+    engine_num: int,
+    custom_stat_loggers: Optional[list[StatLoggerFactory]] = None,
+) -> list[list[StatLoggerBase]]:
+    """Setup logging and prometheus metrics."""
+    if not log_stats:
+        return []
+
+    factories: list[StatLoggerFactory]
+    if custom_stat_loggers is not None:
+        factories = custom_stat_loggers
+    else:
+        factories = [PrometheusStatLogger]
+        if logger.isEnabledFor(logging.INFO):
+            factories.append(LoggingStatLogger)
+
+    stat_loggers: list[list[StatLoggerBase]] = []
+    for i in range(engine_num):
+        per_engine_stat_loggers: list[StatLoggerBase] = []
+        for logger_factory in factories:
+            per_engine_stat_loggers.append(logger_factory(vllm_config, i))
+        stat_loggers.append(per_engine_stat_loggers)
+
+    return stat_loggers