pkg/asset/cluster: stop re-entry in capi installs

This commit prevents users from restarting an aborted install,
i.e. from running create cluster multiple times. This check
is a guardrail that parallels the functionality with terraform
installs.

CAPI installs should be re-entrant, and in my experience this
has generally worked fine, but it is not (yet) well tested. Because
this functionality can work and is useful, the commit includes
an environment variable to allow opting in for re-entry.

Author: patrickdillon

pkg/asset/cluster/cluster.go

@@ -3,6 +3,7 @@ package cluster
 import (
 	"context"
 	"fmt"
+	"os"
 	"path/filepath"
 	"strings"
 
@@ -24,6 +25,7 @@ import (
 	"github.com/openshift/installer/pkg/asset/password"
 	"github.com/openshift/installer/pkg/asset/quota"
 	"github.com/openshift/installer/pkg/asset/rhcos"
+	"github.com/openshift/installer/pkg/clusterapi"
 	infra "github.com/openshift/installer/pkg/infrastructure/platform"
 	typesaws "github.com/openshift/installer/pkg/types/aws"
 	typesazure "github.com/openshift/installer/pkg/types/azure"
@@ -161,9 +163,21 @@ func (c *Cluster) Load(f asset.FileFetcher) (found bool, err error) {
 		return true, err
 	}
 	if len(matches) != 0 {
-		return true, errors.Errorf("terraform state files alread exist.  There may already be a running cluster")
+		return true, fmt.Errorf("terraform state files already exist.  There may already be a running cluster")
 	}
 
+	matches, err = filepath.Glob(filepath.Join(InstallDir, clusterapi.ArtifactsDir, "envtest.kubeconfig"))
+	if err != nil {
+		return true, fmt.Errorf("error checking for existence of envtest.kubeconfig: %w", err)
+	}
+
+	// Cluster-API based installs can be re-entered, but this is an experimental feature
+	// that should be opted into and only used for testing and development.
+	reentrant := strings.EqualFold(os.Getenv("OPENSHIFT_INSTALL_REENTRANT"), "true")
+
+	if !reentrant && len(matches) != 0 {
+		return true, fmt.Errorf("local infrastructure provisioning artifacts already exist. There may already be a running cluster")
+	}
 	return false, nil
 }