Merge pull request #58549 from dims/backup-default-location-for-cloud-config

Automatic merge from submit-queue (batch tested with PRs 58480, 58549). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Use backup location to load cloud config for OpenStack

**What this PR does / why we need it**:

Since we are transitioning to external cloud provider, we need a way
to use the existing cinder volume plugin (from kubelet). With external
cloud manager kubelet will be run with --cloud=provider=external and
no --cloud-config file will be in the command line. So we need a way
to load the openstack config file from somewhere.

Taking a cue from kubeadm, which currently is picking up "/etc/kubernetes/cloud-config"
https://github.com/kubernetes/kubernetes/blob/master/cmd/kubeadm/app/phases/controlplane/manifests.go#L44

let's support the scenario where we fall back to this static location if
there is no cloud provider specified in the command line.

This has been tested with local-up-cluster using the following params:
EXTERNAL_CLOUD_PROVIDER=true
CLOUD_PROVIDER=openstack
CLOUD_CONFIG=/etc/kubernetes/cloud-config


**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

Author: Kubernetes Submit Queue

pkg/volume/cinder/attacher.go

@@ -57,7 +57,7 @@ const (
 )
 
 func (plugin *cinderPlugin) NewAttacher() (volume.Attacher, error) {
-	cinder, err := getCloudProvider(plugin.host.GetCloudProvider())
+	cinder, err := plugin.getCloudProvider()
 	if err != nil {
 		return nil, err
 	}
@@ -305,7 +305,7 @@ type cinderDiskDetacher struct {
 var _ volume.Detacher = &cinderDiskDetacher{}
 
 func (plugin *cinderPlugin) NewDetacher() (volume.Detacher, error) {
-	cinder, err := getCloudProvider(plugin.host.GetCloudProvider())
+	cinder, err := plugin.getCloudProvider()
 	if err != nil {
 		return nil, err
 	}

pkg/volume/cinder/cinder.go

@@ -37,6 +37,10 @@ import (
 	"k8s.io/kubernetes/pkg/volume/util/volumehelper"
 )
 
+const (
+	DefaultCloudConfigPath = "/etc/kubernetes/cloud-config"
+)
+
 // This is the primary entrypoint for volume plugins.
 func ProbeVolumePlugins() []volume.VolumePlugin {
 	return []volume.VolumePlugin{&cinderPlugin{}}
@@ -188,25 +192,31 @@ func (plugin *cinderPlugin) newProvisionerInternal(options volume.VolumeOptions,
 	}, nil
 }
 
-func getCloudProvider(cloudProvider cloudprovider.Interface) (CinderProvider, error) {
-	if cloud, ok := cloudProvider.(*openstack.OpenStack); ok && cloud != nil {
-		return cloud, nil
-	}
-	return nil, fmt.Errorf("wrong cloud type")
-}
-
 func (plugin *cinderPlugin) getCloudProvider() (CinderProvider, error) {
 	cloud := plugin.host.GetCloudProvider()
 	if cloud == nil {
-		glog.Errorf("Cloud provider not initialized properly")
-		return nil, errors.New("Cloud provider not initialized properly")
+		if _, err := os.Stat(DefaultCloudConfigPath); err == nil {
+			var config *os.File
+			config, err = os.Open(DefaultCloudConfigPath)
+			if err != nil {
+				return nil, errors.New(fmt.Sprintf("unable to load OpenStack configuration from default path : %v", err))
+			} else {
+				defer config.Close()
+				cloud, err = cloudprovider.GetCloudProvider(openstack.ProviderName, config)
+				if err != nil {
+					return nil, errors.New(fmt.Sprintf("unable to create OpenStack cloud provider from default path : %v", err))
+				}
+			}
+		} else {
+			return nil, errors.New(fmt.Sprintf("OpenStack cloud provider was not initialized properly : %v", err))
+		}
 	}
 
 	switch cloud := cloud.(type) {
 	case *openstack.OpenStack:
 		return cloud, nil
 	default:
-		return nil, errors.New("Invalid cloud provider: expected OpenStack.")
+		return nil, errors.New("invalid cloud provider: expected OpenStack")
 	}
 }