[Core] Add HOST_CONTROLLERS check for clouds (#3407)

* host_controllers

* host_controllers

* host_controllers

sky/clouds/cloud.py

@@ -42,6 +42,7 @@ class CloudImplementationFeatures(enum.Enum):
     CUSTOM_DISK_TIER = 'custom_disk_tier'
     OPEN_PORTS = 'open_ports'
     STORAGE_MOUNTING = 'storage_mounting'
+    HOST_CONTROLLERS = 'host_controllers'  # Can run spot/serve controllers
 
 
 class Region(collections.namedtuple('Region', ['name'])):

sky/clouds/kubernetes.py

@@ -64,6 +64,13 @@ class Kubernetes(clouds.Cloud):
                                                              'tiers are not '
                                                              'supported in '
                                                              'Kubernetes.',
+        # Kubernetes may be using exec-based auth, which may not work by
+        # directly copying the kubeconfig file to the controller.
+        # Support for service accounts for auth will be added in #3377, which
+        # will allow us to support hosting controllers.
+        clouds.CloudImplementationFeatures.HOST_CONTROLLERS: 'Kubernetes can '
+                                                             'not host '
+                                                             'controllers.',
     }
 
     IMAGE_CPU = 'skypilot:cpu-ubuntu-2004'

sky/execution.py

@@ -234,6 +234,10 @@ def _execute(
     # Requested features that some clouds support and others don't.
     requested_features = set()
 
+    if controller_utils.Controllers.from_name(cluster_name) is not None:
+        requested_features.add(
+            clouds.CloudImplementationFeatures.HOST_CONTROLLERS)
+
     # Add requested features from the task
     requested_features |= task.get_required_cloud_features()