config: recognize Ignition configs and no-op

config/ignition.go

@@ -0,0 +1,26 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package config
+
+import (
+	"encoding/json"
+)
+
+func IsIgnitionConfig(userdata string) bool {
+	var cfg struct {
+		Version *int `json:"ignitionVersion" yaml:"ignition_version"`
+	}
+	return (json.Unmarshal([]byte(userdata), &cfg) == nil && cfg.Version != nil)
+}

config/validate/validate.go

@@ -40,6 +40,8 @@ func Validate(userdataBytes []byte) (Report, error) {
 		return Report{}, nil
 	case config.IsScript(string(userdataBytes)):
 		return Report{}, nil
+	case config.IsIgnitionConfig(string(userdataBytes)):
+		return Report{}, nil
 	case config.IsCloudConfig(string(userdataBytes)):
 		return validateCloudConfig(userdataBytes, Rules)
 	default:

config/validate/validate_test.go

@@ -111,6 +111,16 @@ func TestValidate(t *testing.T) {
 		{
 			config: "#!/bin/bash\necho hey",
 		},
+		{
+			config: "{}",
+			report: Report{entries: []Entry{{entryError, `must be "#cloud-config" or begin with "#!"`, 1}}},
+		},
+		{
+			config: `{"ignitionVersion":0}`,
+		},
+		{
+			config: `{"ignitionVersion":1}`,
+		},
 	}
 
 	for i, tt := range tests {

coreos-cloudinit.go

@@ -200,16 +200,20 @@ func main() {
 
 	var ccu *config.CloudConfig
 	var script *config.Script
-	if ud, err := initialize.ParseUserData(userdata); err != nil {
-		fmt.Printf("Failed to parse user-data: %v\nContinuing...\n", err)
-		failure = true
-	} else {
+	switch ud, err := initialize.ParseUserData(userdata); err {
+	case initialize.ErrIgnitionConfig:
+		fmt.Printf("Detected an Ignition config. Exiting...")
+		os.Exit(0)
+	case nil:
 		switch t := ud.(type) {
 		case *config.CloudConfig:
 			ccu = t
 		case *config.Script:
 			script = t
 		}
+	default:
+		fmt.Printf("Failed to parse user-data: %v\nContinuing...\n", err)
+		failure = true
 	}
 
 	fmt.Println("Merging cloud-config from meta-data and user-data")

initialize/user_data.go

@@ -21,6 +21,10 @@ import (
 	"github.com/coreos/coreos-cloudinit/config"
 )
 
+var (
+	ErrIgnitionConfig = errors.New("not a config (found Ignition)")
+)
+
 func ParseUserData(contents string) (interface{}, error) {
 	if len(contents) == 0 {
 		return nil, nil
@@ -33,6 +37,8 @@ func ParseUserData(contents string) (interface{}, error) {
 	case config.IsCloudConfig(contents):
 		log.Printf("Parsing user-data as cloud-config")
 		return config.NewCloudConfig(contents)
+	case config.IsIgnitionConfig(contents):
+		return nil, ErrIgnitionConfig
 	default:
 		return nil, errors.New("Unrecognized user-data format")
 	}