[serve] Prevent mixing single/multi-app config deployment

dashboard/modules/serve/serve_agent.py

@@ -12,6 +12,7 @@
     CURRENT_VERSION,
     VersionResponse,
 )
+from ray.exceptions import RayTaskError
 
 logger = logging.getLogger(__name__)
 logger.setLevel(logging.INFO)
@@ -228,9 +229,15 @@ def submit_config(self, config):
                 ),
             )
 
-        client.deploy_apps(config)
-
-        return Response()
+        try:
+            client.deploy_apps(config)
+        except RayTaskError as e:
+            return Response(
+                status=400,
+                text=str(e),
+            )
+        else:
+            return Response()
 
     async def get_serve_controller(self):
         """Gets the ServeController to the this cluster's Serve app.

dashboard/modules/serve/tests/test_serve_agent.py

@@ -557,6 +557,106 @@ def applications_running():
     print("Finished checking application details.")
 
 
+@pytest.mark.skipif(sys.platform == "darwin", reason="Flaky on OSX.")
+def test_deploy_single_then_multi(ray_start_stop):
+    world_import_path = "ray.serve.tests.test_config_files.world.DagNode"
+    pizza_import_path = "ray.serve.tests.test_config_files.pizza.serve_dag"
+    multi_app_config = {
+        "host": "127.0.0.1",
+        "port": 8000,
+        "applications": [
+            {
+                "name": "app1",
+                "route_prefix": "/app1",
+                "import_path": world_import_path,
+            },
+            {
+                "name": "app2",
+                "route_prefix": "/app2",
+                "import_path": pizza_import_path,
+            },
+        ],
+    }
+    single_app_config = {
+        "host": "127.0.0.1",
+        "port": 8000,
+        "import_path": world_import_path,
+    }
+
+    def check_app():
+        wait_for_condition(
+            lambda: requests.post("http://localhost:8000/").text == "wonderful world",
+            timeout=15,
+        )
+
+    # Deploy single app config
+    deploy_and_check_config(single_app_config)
+    check_app()
+
+    # Deploying multi app config afterwards should fail
+    put_response = requests.put(GET_OR_PUT_URL_V2, json=multi_app_config, timeout=5)
+    assert put_response.status_code == 400
+    print(put_response.text)
+
+    # The original application should still be up and running
+    check_app()
+
+
+@pytest.mark.skipif(sys.platform == "darwin", reason="Flaky on OSX.")
+def test_deploy_multi_then_single(ray_start_stop):
+    world_import_path = "ray.serve.tests.test_config_files.world.DagNode"
+    pizza_import_path = "ray.serve.tests.test_config_files.pizza.serve_dag"
+    multi_app_config = {
+        "host": "127.0.0.1",
+        "port": 8000,
+        "applications": [
+            {
+                "name": "app1",
+                "route_prefix": "/app1",
+                "import_path": world_import_path,
+            },
+            {
+                "name": "app2",
+                "route_prefix": "/app2",
+                "import_path": pizza_import_path,
+            },
+        ],
+    }
+    single_app_config = {
+        "host": "127.0.0.1",
+        "port": 8000,
+        "import_path": world_import_path,
+    }
+
+    def check_apps():
+        wait_for_condition(
+            lambda: requests.post("http://localhost:8000/app1").text
+            == "wonderful world",
+            timeout=15,
+        )
+        wait_for_condition(
+            lambda: requests.post("http://localhost:8000/app2", json=["ADD", 2]).json()
+            == "4 pizzas please!",
+            timeout=15,
+        )
+        wait_for_condition(
+            lambda: requests.post("http://localhost:8000/app2", json=["MUL", 2]).json()
+            == "6 pizzas please!",
+            timeout=15,
+        )
+
+    # Deploy multi app config
+    deploy_config_multi_app(multi_app_config)
+    check_apps()
+
+    # Deploying single app config afterwards should fail
+    put_response = requests.put(GET_OR_PUT_URL, json=single_app_config, timeout=5)
+    assert put_response.status_code == 400
+
+    # The original applications should still be up and running
+    check_apps()
+
+
 @pytest.mark.skipif(sys.platform == "darwin", reason="Flaky on OSX.")
 def test_serve_namespace(ray_start_stop):
     """

python/ray/serve/_private/client.py

@@ -314,6 +314,18 @@ def deploy_apps(
         config: Union[ServeApplicationSchema, ServeDeploySchema],
         _blocking: bool = False,
     ) -> None:
+        """Starts a task on the controller that deploys application(s) from a config.
+
+        Args:
+            config: A single-application config (ServeApplicationSchema) or a
+                multi-application config (ServeDeploySchema)
+            _blocking: Whether to block until the application is running.
+
+        Raises:
+            RayTaskError: If the deploy task on the controller fails. This can be
+                because a single-app config was deployed after deploying a multi-app
+                config, or vice versa.
+        """
         ray.get(self._controller.deploy_apps.remote(config))
 
         if _blocking:

python/ray/serve/_private/common.py

@@ -326,3 +326,9 @@ def __eq__(self, other):
                 self._hash == other._hash,
             ]
         )
+
+
+class ServeDeployMode(str, Enum):
+    UNSET = "UNSET"
+    SINGLE_APP = "SINGLE_APP"
+    MULTI_APP = "MULTI_APP"

python/ray/serve/controller.py

@@ -23,6 +23,7 @@
     NodeId,
     RunningReplicaInfo,
     StatusOverview,
+    ServeDeployMode,
 )
 from ray.serve.config import DeploymentConfig, HTTPOptions, ReplicaConfig
 from ray.serve._private.constants import (
@@ -39,6 +40,7 @@
 from ray.serve._private.http_state import HTTPState
 from ray.serve._private.logging_utils import configure_component_logger
 from ray.serve._private.long_poll import LongPollHost
+from ray.serve.exceptions import RayServeException
 from ray.serve.schema import (
     ServeApplicationSchema,
     ServeDeploySchema,
@@ -153,6 +155,9 @@ async def __init__(
             self.deployment_state_manager
         )
 
+        # Keep track of single-app vs multi-app
+        self.deploy_mode = ServeDeployMode.UNSET
+
         run_background_task(self.run_control_loop())
 
         self._recover_config_from_checkpoint()
@@ -490,26 +495,31 @@ def deploy_apps(
         # deprecate such usage.
         if isinstance(config, ServeApplicationSchema):
             config = config.to_deploy_schema()
+            if self.deploy_mode == ServeDeployMode.MULTI_APP:
+                raise RayServeException(
+                    "You are trying to deploy a single-application config, however "
+                    "a multi-application config has been deployed to the current "
+                    "Serve instance already. Mixing single-app and multi-app is not "
+                    "allowed. Please either redeploy using the multi-application "
+                    "config format `ServeDeploySchema`, or shutdown and restart Serve "
+                    "to submit a single-app config of format `ServeApplicationSchema`. "
+                    "If you are using the REST API, you can submit a single-app config "
+                    "to the single-app API endpoint `/api/serve/deployments/`."
+                )
+            self.deploy_mode = ServeDeployMode.SINGLE_APP
         else:
-            # TODO (zcin): ServeApplicationSchema still needs to have host and port
-            # fields to support single-app mode, but in multi-app mode the host and port
-            # fields at the top-level deploy config is used instead. Eventually, after
-            # migration, we should remove these fields from ServeApplicationSchema.
-            host, port = config.host, config.port
-            for app_config in config.applications:
-                app_config_dict = app_config.dict(exclude_unset=True)
-                if "host" in app_config_dict:
-                    logger.info(
-                        f"Host {app_config_dict['host']} is set in the config for "
-                        f"application `{app_config.name}`. This will be ignored, as "
-                        f"the host {host} from the top level deploy config is used."
-                    )
-                if "port" in app_config:
-                    logger.info(
-                        f"Port {app_config_dict['port']} is set in the config for "
-                        f"application `{app_config.name}`. This will be ignored, as "
-                        f"the port {port} from the top level deploy config is used."
-                    )
+            if self.deploy_mode == ServeDeployMode.SINGLE_APP:
+                raise RayServeException(
+                    "You are trying to deploy a multi-application config, however "
+                    "a single-application config has been deployed to the current "
+                    "Serve instance already. Mixing single-app and multi-app is not "
+                    "allowed. Please either redeploy using the single-application "
+                    "config format `ServeApplicationSchema`, or shutdown and restart "
+                    "Serve to submit a multi-app config of format `ServeDeploySchema`. "
+                    "If you are using the REST API, you can submit a multi-app config "
+                    "to the the multi-app API endpoint `/api/serve/applications/`."
+                )
+            self.deploy_mode = ServeDeployMode.MULTI_APP
 
         if not deployment_time:
             deployment_time = time.time()