[BugFix] Fix multiple/duplicate stdout prefixes (#36822)

Signed-off-by: Nick Hill <nickhill123@gmail.com>

vllm/entrypoints/cli/serve.py

@@ -21,7 +21,6 @@ from vllm.usage.usage_lib import UsageContext
 from vllm.utils.argparse_utils import FlexibleArgumentParser
 from vllm.utils.network_utils import get_tcp_uri
 from vllm.utils.system_utils import decorate_logs, set_process_title
-from vllm.v1.engine.core import EngineCoreProc
 from vllm.v1.engine.utils import CoreEngineProcManager, launch_core_engines
 from vllm.v1.executor import Executor
 from vllm.v1.executor.multiproc_executor import MultiprocExecutor
@@ -210,7 +209,6 @@ def run_headless(args: argparse.Namespace):
 
     # Create the engines.
     engine_manager = CoreEngineProcManager(
-        target_fn=EngineCoreProc.run_engine_core,
         local_engine_count=local_engine_count,
         start_index=vllm_config.parallel_config.data_parallel_rank,
         local_start_index=0,

vllm/utils/system_utils.py

@@ -204,7 +204,8 @@ def _add_prefix(file: TextIO, worker_name: str, pid: int) -> None:
         prefix = f"({worker_name} pid={pid}) "
     else:
         prefix = f"{CYAN}({worker_name} pid={pid}){RESET} "
-    file_write = file.write
+    # Use the original write to avoid nesting prefixes on repeated calls.
+    file_write = getattr(file, "_original_write", file.write)
 
     def write_with_prefix(s: str):
         if not s:
@@ -224,6 +225,7 @@ def _add_prefix(file: TextIO, worker_name: str, pid: int) -> None:
         file.start_new_line = False  # type: ignore[attr-defined]
 
     file.start_new_line = True  # type: ignore[attr-defined]
+    file._original_write = file_write  # type: ignore[attr-defined]
     file.write = write_with_prefix  # type: ignore[method-assign]
 
 

vllm/v1/engine/core.py

@@ -1045,19 +1045,11 @@ class EngineCoreProc(EngineCore):
             data_parallel = parallel_config.data_parallel_size > 1 or dp_rank > 0
             if data_parallel:
                 parallel_config.data_parallel_rank_local = local_dp_rank
-                maybe_init_worker_tracer(
-                    instrumenting_module_name="vllm.engine_core",
-                    process_kind="engine_core",
-                    process_name=f"EngineCore_DP{dp_rank}",
-                )
-                set_process_title("EngineCore", f"DP{dp_rank}")
+                process_title = f"EngineCore_DP{dp_rank}"
             else:
-                maybe_init_worker_tracer(
-                    instrumenting_module_name="vllm.engine_core",
-                    process_kind="engine_core",
-                    process_name="EngineCore",
-                )
-                set_process_title("EngineCore")
+                process_title = "EngineCore"
+            set_process_title(process_title)
+            maybe_init_worker_tracer("vllm.engine_core", "engine_core", process_title)
             decorate_logs()
 
             if data_parallel and vllm_config.kv_transfer_config is not None:

vllm/v1/engine/utils.py

@@ -4,7 +4,7 @@
 import contextlib
 import os
 import weakref
-from collections.abc import Callable, Iterator
+from collections.abc import Iterator
 from dataclasses import dataclass
 from enum import Enum, auto
 from multiprocessing import Process, connection
@@ -85,7 +85,6 @@ class CoreEngineProcManager:
 
     def __init__(
         self,
-        target_fn: Callable,
         local_engine_count: int,
         start_index: int,
         local_start_index: int,
@@ -108,6 +107,10 @@ class CoreEngineProcManager:
         if client_handshake_address:
             common_kwargs["client_handshake_address"] = client_handshake_address
 
+        is_dp = vllm_config.parallel_config.data_parallel_size > 1
+
+        from vllm.v1.engine.core import EngineCoreProc
+
         self.processes: list[BaseProcess] = []
         local_dp_ranks = []
         for index in range(local_engine_count):
@@ -118,35 +121,27 @@ class CoreEngineProcManager:
             local_dp_ranks.append(local_index)
             self.processes.append(
                 context.Process(
-                    target=target_fn,
-                    name=f"EngineCore_DP{global_index}",
+                    target=EngineCoreProc.run_engine_core,
+                    name=f"EngineCore_DP{global_index}" if is_dp else "EngineCore",
                     kwargs=common_kwargs
-                    | {
-                        "dp_rank": global_index,
-                        "local_dp_rank": local_index,
-                    },
+                    | {"dp_rank": global_index, "local_dp_rank": local_index},
                 )
             )
 
         self._finalizer = weakref.finalize(self, shutdown, self.processes)
 
-        data_parallel = vllm_config.parallel_config.data_parallel_size > 1
         try:
             for proc, local_dp_rank in zip(self.processes, local_dp_ranks):
                 # Adjust device control in DP for non-CUDA platforms
                 # as well as external and ray launchers
                 # For CUDA platforms, we use torch.cuda.set_device()
-                with (
-                    set_device_control_env_var(vllm_config, local_dp_rank)
-                    if (
-                        data_parallel
-                        and (
+                if is_dp and (
                     not current_platform.is_cuda_alike()
                     or vllm_config.parallel_config.use_ray
-                        )
-                    )
-                    else contextlib.nullcontext()
                 ):
+                    with set_device_control_env_var(vllm_config, local_dp_rank):
+                        proc.start()
+                else:
                     proc.start()
         finally:
             # Kill other procs if not all are running.
@@ -926,12 +921,9 @@ def launch_core_engines(
     with zmq_socket_ctx(
         local_handshake_address, zmq.ROUTER, bind=True
     ) as handshake_socket:
-        from vllm.v1.engine.core import EngineCoreProc
-
         # Start local engines.
         if local_engine_count:
             local_engine_manager = CoreEngineProcManager(
-                EngineCoreProc.run_engine_core,
                 vllm_config=vllm_config,
                 executor_class=executor_class,
                 log_stats=log_stats,