fix serve start namespace issue and add test (#16291)

python/ray/serve/BUILD

@@ -229,6 +229,14 @@ py_test(
     deps = [":serve_lib"],
 )
 
+py_test(
+    name = "test_cli",
+    size = "small",
+    srcs = serve_tests_srcs,
+    tags = ["exclusive"],
+    deps = [":serve_lib"],
+)
+
 # Runs test_api and test_failure with injected failures in the controller.
 py_test(
    name = "test_controller_crashes",

python/ray/serve/scripts.py

@@ -18,8 +18,15 @@ from ray.serve.constants import DEFAULT_HTTP_HOST, DEFAULT_HTTP_PORT
     type=str,
     help="Address of the running Ray cluster to connect to. "
     "Defaults to \"auto\".")
-def cli(address):
-    ray.init(address=address)
+@click.option(
+    "--namespace",
+    "-n",
+    default="serve",
+    required=False,
+    type=str,
+    help="Ray namespace to connect to. Defaults to \"serve\".")
+def cli(address, namespace):
+    ray.init(address=address, namespace=namespace)
 
 
 @cli.command(help="Start a detached Serve instance on the Ray cluster.")

python/ray/serve/tests/test_cli.py

@@ -0,0 +1,31 @@
+import subprocess
+import sys
+
+import pytest
+
+
+@pytest.fixture
+def ray_start_stop():
+    subprocess.check_output(["ray", "start", "--head"])
+    yield
+    subprocess.check_output(["ray", "stop", "--force"])
+
+
+def test_start_shutdown(ray_start_stop):
+    with pytest.raises(subprocess.CalledProcessError):
+        subprocess.check_output(["serve", "shutdown"])
+
+    subprocess.check_output(["serve", "start"])
+    subprocess.check_output(["serve", "shutdown"])
+
+
+def test_start_shutdown_in_namespace(ray_start_stop):
+    with pytest.raises(subprocess.CalledProcessError):
+        subprocess.check_output(["serve", "-n", "test", "shutdown"])
+
+    subprocess.check_output(["serve", "-n", "test", "start"])
+    subprocess.check_output(["serve", "-n", "test", "shutdown"])
+
+
+if __name__ == "__main__":
+    sys.exit(pytest.main(["-v", "-s", __file__]))