Export function template (#11923)

A new subcommand is added under `export` named `function`. This command prints the loadable template to stdout for enabled functions.

```
$ ./functionbeat export function cloudwatch
```

I extracted generating templates from `CLIManager`. Now it has a `TemplateBuilder` which constructs the template for the manager. A template builder can be retrieved from a provider, as generating templates is specific to providers. Thus, `CLIManager` does not need to know about the provider anymore.

CHANGELOG.next.asciidoc

@@ -237,6 +237,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 *Functionbeat*
 
 - New options to configure roles and VPC. {pull}11779[11779]
+- Export automation templates used to create functions. {pull}11923[11923]
 
 *Winlogbeat*
 

libbeat/tests/system/beat/beat.py

@@ -360,6 +360,18 @@ def get_log(self, logfile=None):
 
         return data
 
+    def get_log_lines(self, logfile=None):
+        """
+        Returns the log lines as a list of strings
+        """
+        if logfile is None:
+            logfile = self.beat_name + ".log"
+
+        with open(os.path.join(self.working_dir, logfile), 'r') as f:
+            data = f.readlines()
+
+        return data
+
     def wait_log_contains(self, msg, logfile=None,
                           max_timeout=10, poll_interval=0.1,
                           name="log_contains",

x-pack/functionbeat/cmd/provider_cmd.go

@@ -5,6 +5,7 @@
 package cmd
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 
@@ -18,8 +19,7 @@ import (
 
 var output string
 
-// TODO: Add List() subcommand.
-func handler() (*cliHandler, error) {
+func initProvider() (provider.Provider, error) {
 	b, err := instance.NewInitializedBeat(instance.Settings{Name: Name})
 	if err != nil {
 		return nil, err
@@ -35,7 +35,12 @@ func handler() (*cliHandler, error) {
 		return nil, err
 	}
 
-	provider, err := provider.NewProvider(cfg)
+	return provider.NewProvider(cfg)
+}
+
+// TODO: Add List() subcommand.
+func handler() (*cliHandler, error) {
+	provider, err := initProvider()
 	if err != nil {
 		return nil, err
 	}
@@ -99,3 +104,28 @@ func genPackageCmd() *cobra.Command {
 	cmd.Flags().StringVarP(&output, "output", "o", "", "full path to the package")
 	return cmd
 }
+
+func genExportFunctionCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "function",
+		Short: "Export function template",
+		Run: cli.RunWith(func(_ *cobra.Command, args []string) error {
+			p, err := initProvider()
+			if err != nil {
+				return err
+			}
+			builder, err := p.TemplateBuilder()
+			if err != nil {
+				return err
+			}
+			for _, name := range args {
+				template, err := builder.RawTemplate(name)
+				if err != nil {
+					return fmt.Errorf("error generating raw template for %s: %+v", name, err)
+				}
+				fmt.Println(template)
+			}
+			return nil
+		}),
+	}
+}

x-pack/functionbeat/cmd/root.go

@@ -27,4 +27,11 @@ func init() {
 	RootCmd.AddCommand(genUpdateCmd())
 	RootCmd.AddCommand(genRemoveCmd())
 	RootCmd.AddCommand(genPackageCmd())
+
+	addBeatSpecificSubcommands()
+}
+
+func addBeatSpecificSubcommands() {
+	RootCmd.ExportCmd.Short = "Export current config, index template or function"
+	RootCmd.ExportCmd.AddCommand(genExportFunctionCmd())
 }

x-pack/functionbeat/provider/aws/aws.go

@@ -12,7 +12,7 @@ import (
 // Bundle exposes the trigger supported by the AWS provider.
 var Bundle = provider.MustCreate(
 	"aws",
-	provider.NewDefaultProvider("aws", NewCLI),
+	provider.NewDefaultProvider("aws", NewCLI, NewTemplateBuilder),
 	feature.NewDetails("AWS Lambda", "listen to events on AWS lambda", feature.Stable),
 ).MustAddFunction("cloudwatch_logs",
 	NewCloudwatchLogs,