configdrive: Use the EC2 metadata over OpenStack

Standardize on specific EC2 and OpenStack versions and add tests.

datasource/configdrive.go

@@ -8,10 +8,11 @@ import (
 
 type configDrive struct {
 	root     string
+	readFile func(filename string) ([]byte, error)
 }
 
 func NewConfigDrive(root string) *configDrive {
-	return &configDrive{path.Join(root, "openstack")}
+	return &configDrive{root, ioutil.ReadFile}
 }
 
 func (cd *configDrive) IsAvailable() bool {
@@ -24,23 +25,38 @@ func (cd *configDrive) AvailabilityChanges() bool {
 }
 
 func (cd *configDrive) ConfigRoot() string {
-	return cd.root
+	return cd.openstackRoot()
 }
 
+// FetchMetadata attempts to retrieve metadata from ec2/2009-04-04/meta_data.json.
 func (cd *configDrive) FetchMetadata() ([]byte, error) {
-	return cd.readFile("meta_data.json")
+	return cd.tryReadFile(path.Join(cd.ec2Root(), "meta_data.json"))
 }
 
+// FetchUserdata attempts to retrieve the userdata from ec2/2009-04-04/user_data.
+// If no data is found, it will attempt to read from openstack/latest/user_data.
 func (cd *configDrive) FetchUserdata() ([]byte, error) {
-	return cd.readFile("user_data")
+	bytes, err := cd.tryReadFile(path.Join(cd.ec2Root(), "user_data"))
+	if bytes == nil && err == nil {
+		bytes, err = cd.tryReadFile(path.Join(cd.openstackRoot(), "user_data"))
+	}
+	return bytes, err
 }
 
 func (cd *configDrive) Type() string {
 	return "cloud-drive"
 }
 
-func (cd *configDrive) readFile(filename string) ([]byte, error) {
+func (cd *configDrive) ec2Root() string {
-	data, err := ioutil.ReadFile(path.Join(cd.root, "latest", filename))
+	return path.Join(cd.root, "ec2", Ec2ApiVersion)
+}
+
+func (cd *configDrive) openstackRoot() string {
+	return path.Join(cd.root, "openstack", "latest")
+}
+
+func (cd *configDrive) tryReadFile(filename string) ([]byte, error) {
+	data, err := cd.readFile(filename)
 	if os.IsNotExist(err) {
 		err = nil
 	}

datasource/configdrive_test.go

@@ -0,0 +1,114 @@
+package datasource
+
+import (
+	"os"
+	"testing"
+)
+
+type mockFilesystem []string
+
+func (m mockFilesystem) readFile(filename string) ([]byte, error) {
+	for _, file := range m {
+		if file == filename {
+			return []byte(filename), nil
+		}
+	}
+	return nil, os.ErrNotExist
+}
+
+func TestCDFetchMetadata(t *testing.T) {
+	for _, tt := range []struct {
+		root     string
+		filename string
+		files    mockFilesystem
+	}{
+		{
+			"/",
+			"",
+			mockFilesystem{},
+		},
+		{
+			"/",
+			"/ec2/2009-04-04/meta_data.json",
+			mockFilesystem([]string{"/ec2/2009-04-04/meta_data.json"}),
+		},
+		{
+			"/media/configdrive",
+			"/media/configdrive/ec2/2009-04-04/meta_data.json",
+			mockFilesystem([]string{"/media/configdrive/ec2/2009-04-04/meta_data.json"}),
+		},
+	} {
+		cd := configDrive{tt.root, tt.files.readFile}
+		filename, err := cd.FetchMetadata()
+		if err != nil {
+			t.Fatalf("bad error for %q: want %q, got %q", tt, nil, err)
+		}
+		if string(filename) != tt.filename {
+			t.Fatalf("bad path for %q: want %q, got %q", tt, tt.filename, filename)
+		}
+	}
+}
+
+func TestCDFetchUserdata(t *testing.T) {
+	for _, tt := range []struct {
+		root     string
+		filename string
+		files    mockFilesystem
+	}{
+		{
+			"/",
+			"",
+			mockFilesystem{},
+		},
+		{
+			"/",
+			"/ec2/2009-04-04/user_data",
+			mockFilesystem([]string{"/ec2/2009-04-04/user_data"}),
+		},
+		{
+			"/",
+			"/openstack/latest/user_data",
+			mockFilesystem([]string{"/openstack/latest/user_data"}),
+		},
+		{
+			"/",
+			"/ec2/2009-04-04/user_data",
+			mockFilesystem([]string{"/openstack/latest/user_data", "/ec2/2009-04-04/user_data"}),
+		},
+		{
+			"/media/configdrive",
+			"/media/configdrive/ec2/2009-04-04/user_data",
+			mockFilesystem([]string{"/media/configdrive/ec2/2009-04-04/user_data"}),
+		},
+	} {
+		cd := configDrive{tt.root, tt.files.readFile}
+		filename, err := cd.FetchUserdata()
+		if err != nil {
+			t.Fatalf("bad error for %q: want %q, got %q", tt, nil, err)
+		}
+		if string(filename) != tt.filename {
+			t.Fatalf("bad path for %q: want %q, got %q", tt, tt.filename, filename)
+		}
+	}
+}
+
+func TestCDConfigRoot(t *testing.T) {
+	for _, tt := range []struct {
+		root       string
+		configRoot string
+	}{
+		{
+			"/",
+			"/openstack/latest",
+		},
+		{
+			"/media/configdrive",
+			"/media/configdrive/openstack/latest",
+		},
+	} {
+		cd := configDrive{tt.root, nil}
+		if configRoot := cd.ConfigRoot(); configRoot != tt.configRoot {
+			t.Fatalf("bad config root for %q: want %q, got %q", tt, tt.configRoot, configRoot)
+		}
+	}
+}

datasource/datasource.go

@@ -1,5 +1,10 @@
 package datasource
 
+const (
+	Ec2ApiVersion       = "2009-04-04"
+	OpenstackApiVersion = "2012-08-10"
+)
+
 type Datasource interface {
 	IsAvailable() bool
 	AvailabilityChanges() bool

datasource/metadata_service.go

@@ -22,11 +22,9 @@ import (
 
 const (
 	BaseUrl              = "http://169.254.169.254/"
-	Ec2ApiVersion        = "2009-04-04"
 	Ec2UserdataUrl       = BaseUrl + Ec2ApiVersion + "/user-data"
 	Ec2MetadataUrl       = BaseUrl + Ec2ApiVersion + "/meta-data"
-	OpenstackApiVersion  = "openstack/2012-08-10"
+	OpenstackUserdataUrl = BaseUrl + "openstack/" + OpenstackApiVersion + "/user_data"
-	OpenstackUserdataUrl = BaseUrl + OpenstackApiVersion + "/user_data"
 )
 
 type metadataService struct{}

datasource/metadata_service_test.go

@@ -25,7 +25,7 @@ func (t *TestHttpClient) GetRetry(url string) ([]byte, error) {
 	}
 }
 
-func TestFetchAttributes(t *testing.T) {
+func TestMSFetchAttributes(t *testing.T) {
 	for _, s := range []struct {
 		metadata map[string]string
 		err      error
@@ -77,7 +77,7 @@ func TestFetchAttributes(t *testing.T) {
 	}
 }
 
-func TestFetchAttribute(t *testing.T) {
+func TestMSFetchAttribute(t *testing.T) {
 	for _, s := range []struct {
 		metadata map[string]string
 		err      error
@@ -129,7 +129,7 @@ func TestFetchAttribute(t *testing.T) {
 	}
 }
 
-func TestFetchMetadata(t *testing.T) {
+func TestMSFetchMetadata(t *testing.T) {
 	for _, tt := range []struct {
 		metadata map[string]string
 		err      error