[Misc]: allow user to specify port in distributed setting (#4914)

vllm/envs.py

@@ -3,6 +3,7 @@ from typing import TYPE_CHECKING, Any, Callable, Dict, Optional
 
 if TYPE_CHECKING:
     VLLM_HOST_IP: str = ""
+    VLLM_PORT: Optional[int] = None
     VLLM_USE_MODELSCOPE: bool = False
     VLLM_INSTANCE_ID: Optional[str] = None
     VLLM_NCCL_SO_PATH: Optional[str] = None
@@ -96,6 +97,12 @@ environment_variables: Dict[str, Callable[[], Any]] = {
     'VLLM_HOST_IP':
     lambda: os.getenv('VLLM_HOST_IP', "") or os.getenv("HOST_IP", ""),
 
+    # used in distributed environment to manually set the communication port
+    # '0' is used to make mypy happy
+    'VLLM_PORT':
+    lambda: int(os.getenv('VLLM_PORT', '0'))
+    if 'VLLM_PORT' in os.environ else None,
+
     # 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":