Create new response API codes for specific Leave/Join failures (#388)

src/k8s/pkg/k8sd/api/cluster_join.go

@@ -22,6 +22,10 @@ func (e *Endpoints) postClusterJoin(s *state.State, r *http.Request) response.Re
 		return response.BadRequest(fmt.Errorf("invalid hostname %q: %w", req.Name, err))
 	}
 
+	if _, err := e.provider.MicroCluster().Status(r.Context()); err == nil {
+		return NodeInUse(fmt.Errorf("node %q is part of the cluster", hostname))
+	}
+
 	config := map[string]string{}
 	internalToken := types.InternalWorkerNodeToken{}
 	// Check if token is worker token

src/k8s/pkg/k8sd/api/cluster_remove.go

@@ -38,7 +38,7 @@ func (e *Endpoints) postClusterRemove(s *state.State, r *http.Request) response.
 
 	isWorker, err := databaseutil.IsWorkerNode(r.Context(), s, req.Name)
 	if err != nil {
-		return response.InternalError(fmt.Errorf("failed to check if node is control-plane: %w", err))
+		return response.InternalError(fmt.Errorf("failed to check if node is worker: %w", err))
 	}
 	if isWorker {
 		// For worker nodes, we need to manually clean up the kubernetes node and db entry.
@@ -57,7 +57,7 @@ func (e *Endpoints) postClusterRemove(s *state.State, r *http.Request) response.
 	}
 
 	if !isWorker && !isControlPlane {
-		return response.InternalError(fmt.Errorf("node %q is not part of the cluster", req.Name))
+		return NodeUnavailable(fmt.Errorf("node %q is not part of the cluster", req.Name))
 	}
 	return response.SyncResponse(true, nil)
 }

src/k8s/pkg/k8sd/api/response.go

@@ -0,0 +1,20 @@
+package api
+
+import (
+	"github.com/canonical/lxd/lxd/response"
+)
+
+const (
+	// StatusNodeUnavailable is the Http status code that the API returns if the node isn't in the cluster
+	StatusNodeUnavailable = 520
+	// StatusNodeInUse is the Http status code that the API returns if the node is already in the cluster
+	StatusNodeInUse = 521
+)
+
+func NodeUnavailable(err error) response.Response {
+	return response.ErrorResponse(StatusNodeUnavailable, err.Error())
+}
+
+func NodeInUse(err error) response.Response {
+	return response.ErrorResponse(StatusNodeInUse, err.Error())
+}