Use random port for backend

vllm/entrypoints/openai/api_server.py

@@ -45,7 +45,7 @@
     OpenAIServingTokenization)
 from vllm.logger import init_logger
 from vllm.usage.usage_lib import UsageContext
-from vllm.utils import FlexibleArgumentParser
+from vllm.utils import FlexibleArgumentParser, get_open_port
 from vllm.version import __version__ as VLLM_VERSION
 
 TIMEOUT_KEEP_ALIVE = 5  # seconds
@@ -107,15 +107,18 @@ async def build_backend(args) -> AsyncIterator[VLLMBackend]:
     else:
         # remote backend
         ## First need to start the backend process
+        port = get_open_port(envs.VLLM_RPC_PORT)
         rpc_server_process = Process(target=run_rpc_server,
-                                     args=(engine_args, 
-                                           UsageContext.OPENAI_API_SERVER))
+                                     args=(engine_args,
+                                           UsageContext.OPENAI_API_SERVER,
+                                           port))
         rpc_server_process.start()
 
         ## Then build the client for the backend process
         # TODO: figure out a way around passing the tokenizer
-        backend = RPCClient(
-            tokenizer=AutoTokenizer.from_pretrained(args.model))
+        backend = RPCClient(tokenizer=AutoTokenizer.from_pretrained(
+            args.model),
+                            port=port)
         await backend.wait_for_server()
 
         try:

vllm/entrypoints/openai/rpc/__init__.py

@@ -7,7 +7,6 @@
 from vllm.prompt_adapter.request import PromptAdapterRequest
 from vllm.sampling_params import SamplingParams
 
-VLLM_RPC_PATH = "tcp://localhost:5570"
 VLLM_RPC_SUCCESS_STR = "SUCCESS"
 
 

vllm/entrypoints/openai/rpc/client.py

@@ -5,7 +5,7 @@
 import zmq.asyncio
 
 from vllm.config import DecodingConfig, ModelConfig
-from vllm.entrypoints.openai.rpc import (RPC_REQUEST_TYPE, VLLM_RPC_PATH,
+from vllm.entrypoints.openai.rpc import (RPC_REQUEST_TYPE,
                                          VLLM_RPC_SUCCESS_STR, RPCAbortRequest,
                                          RPCGenerateRequest, RPCUtilityRequest)
 from vllm.inputs import PromptInputs
@@ -18,13 +18,14 @@
 class RPCClient:
 
     # TODO: check if opening all these sockets is an antipattern?
-    def __init__(self, tokenizer):
+    def __init__(self, tokenizer, port: int):
         # ZMQ context.
         self.context = zmq.asyncio.Context()
 
         # TODO: do the tokenizer properly.
         self.tokenizer = tokenizer
         self.decoding_config = DecodingConfig()
+        self.path = f"tcp://localhost:{port}"
 
     def close(self):
         """Destroy the ZeroMQ Context."""
@@ -36,7 +37,7 @@ async def _send_one_way_rpc_request(self, request: RPC_REQUEST_TYPE,
 
         # Connect to socket.
         socket = self.context.socket(zmq.constants.DEALER)
-        socket.connect(VLLM_RPC_PATH)
+        socket.connect(self.path)
 
         # Ping RPC Server with request.
         socket.send(pickle.dumps(request, pickle.HIGHEST_PROTOCOL))
@@ -76,7 +77,7 @@ async def get_model_config(self) -> ModelConfig:
 
         # Connect to socket.
         socket = self.context.socket(zmq.constants.DEALER)
-        socket.connect(VLLM_RPC_PATH)
+        socket.connect(self.path)
 
         # Ping RPCServer with GET_MODEL_CONFIG request.
         socket.send(pickle.dumps(RPCUtilityRequest.GET_MODEL_CONFIG))
@@ -122,7 +123,7 @@ async def generate(
         # Note that we use DEALER to enable asynchronous communication
         # to enable streaming.
         socket = self.context.socket(zmq.constants.DEALER)
-        socket.connect(VLLM_RPC_PATH)
+        socket.connect(self.path)
 
         # Send RPCGenerateRequest to the RPCServer.
         socket.send_multipart([

vllm/entrypoints/openai/rpc/server.py

@@ -8,9 +8,8 @@
 from typing_extensions import Never
 
 from vllm import AsyncEngineArgs, AsyncLLMEngine
-from vllm.entrypoints.openai.rpc import (VLLM_RPC_PATH, VLLM_RPC_SUCCESS_STR,
-                                         RPCAbortRequest, RPCGenerateRequest,
-                                         RPCUtilityRequest)
+from vllm.entrypoints.openai.rpc import (VLLM_RPC_SUCCESS_STR, RPCAbortRequest,
+                                         RPCGenerateRequest, RPCUtilityRequest)
 from vllm.logger import init_logger
 from vllm.usage.usage_lib import UsageContext
 
@@ -23,7 +22,7 @@ class RPCServer:
     # Alternative, use a smaller number of sockets with conditioning on the
     # data that is passed through the socket.
     def __init__(self, async_engine_args: AsyncEngineArgs,
-                 usage_context: UsageContext):
+                 usage_context: UsageContext, port: int):
         # Initialize engine first.
         self.engine = AsyncLLMEngine.from_engine_args(async_engine_args,
                                                       usage_context)
@@ -33,7 +32,7 @@ def __init__(self, async_engine_args: AsyncEngineArgs,
 
         # Init socket for readiness state.
         self.socket = self.context.socket(zmq.constants.ROUTER)
-        self.socket.bind(VLLM_RPC_PATH)
+        self.socket.bind(f"tcp://localhost:{port}")
 
     def cleanup(self):
         """Cleanup all resources."""
@@ -51,10 +50,9 @@ async def get_model_config(self, identity):
         """Send the ModelConfig """
         model_config = await self.engine.get_model_config()
 
-        self.socket.send_multipart([
-            identity,
-            pickle.dumps(model_config, pickle.HIGHEST_PROTOCOL)
-        ])
+        self.socket.send_multipart(
+            [identity,
+             pickle.dumps(model_config, pickle.HIGHEST_PROTOCOL)])
 
     async def do_log_stats(self, identity):
         await self.engine.do_log_stats()
@@ -166,6 +164,6 @@ def signal_handler() -> None:
 
 
 def run_rpc_server(async_engine_args: AsyncEngineArgs,
-                   usage_context: UsageContext):
-    server = RPCServer(async_engine_args, usage_context)
+                   usage_context: UsageContext, port: int):
+    server = RPCServer(async_engine_args, usage_context, port)
     asyncio.run(run_server(server))

vllm/envs.py

@@ -4,6 +4,7 @@
 if TYPE_CHECKING:
     VLLM_HOST_IP: str = ""
     VLLM_PORT: Optional[int] = None
+    VLLM_RPC_PORT: int = 5570
     VLLM_USE_MODELSCOPE: bool = False
     VLLM_RINGBUFFER_WARNING_INTERVAL: int = 60
     VLLM_INSTANCE_ID: Optional[str] = None
@@ -142,6 +143,11 @@ def get_default_config_root():
     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_PORT', '5570')),
+
     # If true, will load models from ModelScope instead of Hugging Face Hub.
     # note that the value is true or false, not numbers
     "VLLM_USE_MODELSCOPE":

vllm/utils.py

@@ -384,8 +384,10 @@ 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() -> int:
-    port = envs.VLLM_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
     if port is not None:
         while True:
             try: