Allow control of some serve configuration via env vars (ray-project#4…

…7533)

When a serve app is launched, serve will startup automatically. In
certain places like k8s, it can be difficult to preconfigure serve (e.g.
in the [ray-cluster helm
chart](https://github.com/ray-project/kuberay/blob/master/helm-chart/ray-cluster/values.yaml)
there is no ability to set the default serve arguments).

This means you need to either be explicit when you start serve, or if it
starts up automatically you may need to shut it down, then restart it,
which is inconvenient.

Signed-off-by: Tim Paine <[email protected]>
Signed-off-by: ujjawal-khare <[email protected]>

python/ray/serve/_private/constants.py

@@ -16,19 +16,21 @@
 SERVE_NAMESPACE = "serve"
 
 #: HTTP Address
-DEFAULT_HTTP_ADDRESS = "http://127.0.0.1:8000"
+DEFAULT_HTTP_ADDRESS = os.environ.get(
+    "RAY_SERVE_DEFAULT_HTTP_ADDRESS", "http://127.0.0.1:8000"
+)
 
 #: HTTP Host
-DEFAULT_HTTP_HOST = "127.0.0.1"
+DEFAULT_HTTP_HOST = os.environ.get("RAY_SERVE_DEFAULT_HTTP_HOST", "127.0.0.1")
 
 #: HTTP Port
-DEFAULT_HTTP_PORT = 8000
+DEFAULT_HTTP_PORT = int(os.environ.get("RAY_SERVE_DEFAULT_HTTP_PORT", 8000))
 
 #: Uvicorn timeout_keep_alive Config
 DEFAULT_UVICORN_KEEP_ALIVE_TIMEOUT_S = 5
 
 #: gRPC Port
-DEFAULT_GRPC_PORT = 9000
+DEFAULT_GRPC_PORT = int(os.environ.get("RAY_SERVE_DEFAULT_GRPC_PORT", 9000))
 
 #: Default Serve application name
 SERVE_DEFAULT_APP_NAME = "default"