cloudinit: merge cloudconfig info from user-data and meta-data

This attempts to retrieve cloudconfigs from two sources: the meta-data
service, and the user-data service. If only one cloudconfig is found,
that is applied to the system. If both services return a cloudconfig,
the two are merged into a single cloudconfig which is then applied to
the system.

Only a subset of parameters are merged (because the meta-data service
currently only partially populates a cloudconfig). In the event of any
conflicts, parameters in the user-data cloudconfig take precedence over
those in the meta-data cloudconfig.

initialize/meta_data.go

@@ -3,8 +3,8 @@ package initialize
 import "encoding/json"
 
 // ParseMetaData parses a JSON blob in the OpenStack metadata service format, and
-// converts it to a CloudConfig
-func ParseMetaData(contents string) (cfg CloudConfig, err error) {
+// converts it to a partially hydrated CloudConfig
+func ParseMetaData(contents string) (cfg *CloudConfig, err error) {
 	var metadata struct {
 		SSHAuthorizedKeyMap map[string]string `json:"public_keys"`
 		Hostname            string            `json:"hostname"`

initialize/user_data.go

@@ -19,14 +19,9 @@ func ParseUserData(contents string) (interface{}, error) {
 	if strings.HasPrefix(header, "#!") {
 		log.Printf("Parsing user-data as script")
 		return system.Script(contents), nil
-
 	} else if header == "#cloud-config" {
 		log.Printf("Parsing user-data as cloud-config")
-		cfg, err := NewCloudConfig(contents)
-		if err != nil {
-			log.Fatal(err.Error())
-		}
-		return *cfg, nil
+		return NewCloudConfig(contents)
 	} else {
 		return nil, fmt.Errorf("Unrecognized user-data header: %s", header)
 	}

initialize/user_data_test.go

@@ -37,7 +37,7 @@ func TestParseConfigCRLF(t *testing.T) {
 		t.Fatalf("Failed parsing config: %v", err)
 	}
 
-	cfg := ud.(CloudConfig)
+	cfg := ud.(*CloudConfig)
 
 	if cfg.Hostname != "foo" {
 		t.Error("Failed parsing hostname from config")