[ BugFix ] Move `zmq` frontend to IPC instead of TCP (#7222)

vllm/entrypoints/openai/api_server.py

@@ -43,7 +43,7 @@ from vllm.entrypoints.openai.serving_tokenization import (
     OpenAIServingTokenization)
 from vllm.logger import init_logger
 from vllm.usage.usage_lib import UsageContext
-from vllm.utils import FlexibleArgumentParser, get_open_port
+from vllm.utils import FlexibleArgumentParser, get_open_zmq_ipc_path
 from vllm.version import __version__ as VLLM_VERSION
 
 TIMEOUT_KEEP_ALIVE = 5  # seconds
@@ -106,16 +106,20 @@ async def build_async_engine_client(args) -> AsyncIterator[AsyncEngineClient]:
 
     # Otherwise, use the multiprocessing AsyncLLMEngine.
     else:
+        # Select random path for IPC.
+        rpc_path = get_open_zmq_ipc_path()
+        logger.info("Multiprocessing frontend to use %s for RPC Path.",
+                    rpc_path)
+
         # Start RPCServer in separate process (holds the AsyncLLMEngine).
-        port = get_open_port(envs.VLLM_RPC_PORT)
         rpc_server_process = Process(target=run_rpc_server,
                                      args=(engine_args,
                                            UsageContext.OPENAI_API_SERVER,
-                                           port))
+                                           rpc_path))
         rpc_server_process.start()
 
         # Build RPCClient, which conforms to AsyncEngineClient Protocol.
-        async_engine_client = AsyncEngineRPCClient(port)
+        async_engine_client = AsyncEngineRPCClient(rpc_path)
         await async_engine_client.setup()
 
         try:

vllm/entrypoints/openai/rpc/client.py

@@ -21,9 +21,9 @@ from vllm.transformers_utils.tokenizer_group import init_tokenizer_from_configs
 
 class AsyncEngineRPCClient:
 
-    def __init__(self, port: int):
+    def __init__(self, rpc_path: str):
         self.context = zmq.asyncio.Context()
-        self.path = f"tcp://localhost:{port}"
+        self.rpc_path = rpc_path
 
     async def setup(self):
         """Setup the client before it starts sending server requests."""
@@ -58,7 +58,7 @@ class AsyncEngineRPCClient:
         # to enable streaming.
         socket = self.context.socket(zmq.constants.DEALER)
         try:
-            socket.connect(self.path)
+            socket.connect(self.rpc_path)
             yield socket
         finally:
             socket.close()

vllm/entrypoints/openai/rpc/server.py

@@ -20,7 +20,7 @@ logger = init_logger(__name__)
 class AsyncEngineRPCServer:
 
     def __init__(self, async_engine_args: AsyncEngineArgs,
-                 usage_context: UsageContext, port: int):
+                 usage_context: UsageContext, rpc_path: str):
         # Initialize engine first.
         self.engine = AsyncLLMEngine.from_engine_args(async_engine_args,
                                                       usage_context)
@@ -30,9 +30,7 @@ class AsyncEngineRPCServer:
 
         # Init socket for readiness state.
         self.socket = self.context.socket(zmq.constants.ROUTER)
-        # Note numeric form of localhost should be used for zmq bind(),
-        # see https://stackoverflow.com/a/8958414
-        self.socket.bind(f"tcp://127.0.0.1:{port}")
+        self.socket.bind(rpc_path)
 
     def cleanup(self):
         """Cleanup all resources."""
@@ -213,6 +211,6 @@ async def run_server(server: AsyncEngineRPCServer):
 
 
 def run_rpc_server(async_engine_args: AsyncEngineArgs,
-                   usage_context: UsageContext, port: int):
-    server = AsyncEngineRPCServer(async_engine_args, usage_context, port)
+                   usage_context: UsageContext, rpc_path: str):
+    server = AsyncEngineRPCServer(async_engine_args, usage_context, rpc_path)
     asyncio.run(run_server(server))

vllm/envs.py

 import os
+import tempfile
 from typing import TYPE_CHECKING, Any, Callable, Dict, Optional
 
 if TYPE_CHECKING:
     VLLM_HOST_IP: str = ""
     VLLM_PORT: Optional[int] = None
-    VLLM_RPC_PORT: int = 5570
+    VLLM_RPC_BASE_PATH: str = tempfile.gettempdir()
     VLLM_USE_MODELSCOPE: bool = False
     VLLM_RINGBUFFER_WARNING_INTERVAL: int = 60
     VLLM_INSTANCE_ID: Optional[str] = None
@@ -142,10 +143,10 @@ environment_variables: Dict[str, Callable[[], Any]] = {
     lambda: int(os.getenv('VLLM_PORT', '0'))
     if 'VLLM_PORT' in os.environ else None,
 
-    # used when the frontend api server is running in multi-processing mode,
-    # to communicate with the backend engine process over ZMQ.
-    'VLLM_RPC_PORT':
-    lambda: int(os.getenv('VLLM_RPC_PORT', '5570')),
+    # path used for ipc when the frontend api server is running in
+    # multi-processing mode to communicate with the backend engine process.
+    'VLLM_RPC_BASE_PATH':
+    lambda: os.getenv('VLLM_RPC_BASE_PATH', tempfile.gettempdir()),
 
     # If true, will load models from ModelScope instead of Hugging Face Hub.
     # note that the value is true or false, not numbers

vllm/utils.py

@@ -19,6 +19,7 @@ from platform import uname
 from typing import (Any, AsyncGenerator, Awaitable, Callable, Dict, Generic,
                     Hashable, List, Optional, OrderedDict, Set, Tuple, TypeVar,
                     Union, overload)
+from uuid import uuid4
 
 import numpy as np
 import numpy.typing as npt
@@ -484,10 +485,13 @@ def get_distributed_init_method(ip: str, port: int) -> str:
     return f"tcp://[{ip}]:{port}" if ":" in ip else f"tcp://{ip}:{port}"
 
 
-def get_open_port(port: Optional[int] = None) -> int:
-    if port is None:
-        # Default behavior here is to return a port for multi-gpu communication
-        port = envs.VLLM_PORT
+def get_open_zmq_ipc_path() -> str:
+    base_rpc_path = envs.VLLM_RPC_BASE_PATH
+    return f"ipc://{base_rpc_path}/{uuid4()}"
+
+
+def get_open_port() -> int:
+    port = envs.VLLM_PORT
     if port is not None:
         while True:
             try: