[Doc] add env vars to the doc (#4572)

Author: youkaichao

docs/source/index.rst

@@ -75,6 +75,7 @@ Documentation
    serving/deploying_with_docker
    serving/distributed_serving
    serving/metrics
+   serving/env_vars
    serving/usage_stats
    serving/integrations
 

docs/source/serving/env_vars.rst

@@ -0,0 +1,9 @@
+Environment Variables
+========================
+
+vLLM uses the following environment variables to configure the system:
+
+.. literalinclude:: ../../../vllm/envs.py
+    :language: python
+    :start-after: begin-env-vars-definition
+    :end-before: end-env-vars-definition

vllm/envs.py

@@ -28,6 +28,11 @@
     VLLM_USE_RAY_COMPILED_DAG: bool = False
     VLLM_WORKER_MULTIPROC_METHOD: str = "spawn"
 
+# The begin-* and end* here are used by the documentation generator
+# to extract the used env vars.
+
+# begin-env-vars-definition
+
 environment_variables: Dict[str, Callable[[], Any]] = {
     # used in distributed environment to determine the master address
     'VLLM_HOST_IP':
@@ -148,6 +153,8 @@
     lambda: os.getenv("VLLM_WORKER_MULTIPROC_METHOD", "spawn"),
 }
 
+# end-env-vars-definition
+
 
 def __getattr__(name):
     # lazy evaluation of environment variables