Add add_logger API to AsyncLLM

tests/v1/metrics/test_ray_metrics.py

@@ -43,8 +43,8 @@ async def run(self):
                 disable_log_stats=False,
             )
 
-            engine = AsyncLLM.from_engine_args(
-                engine_args, stat_loggers=[RayPrometheusStatLogger])
+            engine = AsyncLLM.from_engine_args(engine_args)
+            await engine.add_logger(RayPrometheusStatLogger)
 
             for i, prompt in enumerate(example_prompts):
                 results = engine.generate(

vllm/v1/engine/async_llm.py

@@ -608,6 +608,25 @@ async def collective_rpc(self,
         return await self.engine_core.collective_rpc_async(
             method, timeout, args, kwargs)
 
+    async def add_logger(self, logger_factory: StatLoggerFactory) -> None:
+        if not self.log_stats:
+            raise RuntimeError(
+                "Stat logging is disabled. Set `disable_log_stats=False` "
+                "argument to enable.")
+
+        engine_num = self.vllm_config.parallel_config.data_parallel_size
+        if len(self.stat_loggers) == 0:
+            self.stat_loggers = [[] for _ in range(engine_num)]
+
+        logger_type = type(logger_factory)
+        for logger in self.stat_loggers[0]:
+            if type(logger) is logger_type:
+                raise KeyError(
+                    f"Logger with type {logger_type} already exists.")
+
+        for i, logger_list in enumerate(self.stat_loggers):
+            logger_list.append(logger_factory(self.vllm_config, i))
+
     @property
     def is_running(self) -> bool:
         # Is None before the loop is started.