Adding generate-config functionality

README.md

@@ -143,6 +143,7 @@ Flags:
       --debug-api                         [ENV: CA_DEBUG_API] Enable Circonus API debug messages
       --debug-cgm                         [ENV: CA_DEBUG_CGM] Enable CGM debug messages
       --debug-dump-metrics string         [ENV: CA_DEBUG_DUMP_METRICS] Directory to dump sent metrics
+      --generate-config string            Generate config file (json|toml|yaml) and exit
   -h, --help                              help for circonus-agent
       --host-etc string                   [ENV: HOST_ETC] Host /etc directory
       --host-proc string                  [ENV: HOST_PROC] Host /proc directory

cmd/root.go

@@ -68,6 +68,21 @@ in JSON format.`,
 			return
 		}
 
+		//
+		// generate tmp config file in etc/ and exit
+		//
+		if viper.GetString(config.KeyGenerateConfig) != "" {
+			f, err := os.Create(fmt.Sprintf("%s/circonus-agent.%s.tmp", defaults.EtcPath, viper.GetString(config.KeyGenerateConfig)))
+			if err != nil {
+				log.Fatal().Err(err).Msg("generate-config")
+			}
+			defer f.Close()
+			if err := config.GenerateConfig(f); err != nil {
+				log.Fatal().Err(err).Msg("generate-config")
+			}
+			return
+		}
+
 		log.Info().
 			Int("pid", os.Getpid()).
 			Str("name", release.NAME).
@@ -1286,6 +1301,19 @@ func init() {
 		}
 	}
 
+	{
+		const (
+			key         = config.KeyGenerateConfig
+			longOpt     = "generate-config"
+			description = "Generate config file (json|toml|yaml) and exit"
+		)
+
+		RootCmd.Flags().String(longOpt, "", description)
+		if err := viper.BindPFlag(key, RootCmd.Flags().Lookup(longOpt)); err != nil {
+			bindFlagError(longOpt, err)
+		}
+	}
+
 	//
 	// Hidden, deprecated flags so old configs don't break - the flags are just ignored
 	//

etc/README.md

@@ -6,10 +6,12 @@ The `etc` directory is used for the main configuration of the Circonus agent, as
 
 File name: `circonus-agent.(json|toml|yaml)`
 
-An example configuration, with default values, can be retrieved using the `--show-config=(json|toml|yaml)`.
+An example configuration, with default values, can be retrieved using the `--show-config=(json|toml|yaml)` or `--generate-config=(json|toml|yaml)`.
 
 ## Configuration file quick start
 
+### Using show-config
+
 Run one of the following (from the base directory where the agent was installed) and edit the resulting configuration file:
 
 
@@ -29,6 +31,26 @@ sbin\circonus-agentd.exe --show-config=yaml > etc\circonus-agent.yaml.tmp
 
 Edit the resulting file to customize configuration settings. When done, rename file to remove the `.tmp` extension. (e.g. `mv etc/circonus-agent.json.tmp` `etc/circonus-agent.json`)
 
+### Using generate-config
+
+Run one of the following (from the base directory where the agent was installed) and edit the resulting configuration file:
+
+```
+sbin/circonus-agentd --generate-config=json
+sbin/circonus-agentd --generate-config=toml
+sbin/circonus-agentd --generate-config=yaml
+```
+
+or, on Windows:
+
+```
+sbin\circonus-agentd.exe --generate-config=json
+sbin\circonus-agentd.exe --generate-config=toml
+sbin\circonus-agentd.exe --generate-config=yaml
+```
+
+Edit the resulting file to customize configuration settings. When done, rename file to remove the `.tmp` extension. (e.g. `mv etc/circonus-agent.json.tmp` `etc/circonus-agent.json`)
+
 ---
 
 # Builtin Collector Configurations

internal/config/config.go

@@ -212,6 +212,9 @@ const (
 	// KeyShowConfig - show configuration and exit
 	KeyShowConfig = "show-config"
 
+	// KeyGenerateConfig - generate temporary config file in given format and exit
+	KeyGenerateConfig = "generate-config"
+
 	// KeyShowVersion - show version information and exit
 	KeyShowVersion = "version"
 
@@ -451,3 +454,35 @@ func ShowConfig(w io.Writer) error {
 	fmt.Fprintln(w, string(data))
 	return nil
 }
+
+// GenerateConfig creates a temp config file in etc/
+func GenerateConfig(w io.Writer) error {
+	var cfg *Config
+	var err error
+	var data []byte
+
+	cfg, err = getConfig()
+	if err != nil {
+		return err
+	}
+
+	format := viper.GetString(KeyGenerateConfig)
+
+	switch format {
+	case "json":
+		data, err = json.MarshalIndent(cfg, " ", "  ")
+	case "yaml":
+		data, err = yaml.Marshal(cfg)
+	case "toml":
+		data, err = toml.Marshal(*cfg)
+	default:
+		return errors.Errorf("unknown config format '%s'", format)
+	}
+
+	if err != nil {
+		return errors.Wrapf(err, "formatting config (%s)", format)
+	}
+
+	fmt.Fprintln(w, string(data))
+	return nil
+}

internal/config/config_test.go

@@ -68,6 +68,38 @@ func TestShowConfig(t *testing.T) {
 	}
 }
 
+func TestGenerateConfig(t *testing.T) {
+	t.Log("Testing ShowConfig")
+	zerolog.SetGlobalLevel(zerolog.Disabled)
+
+	t.Log("YAML")
+	{
+		viper.Set(KeyGenerateConfig, "yaml")
+		err := GenerateConfig(ioutil.Discard)
+		if err != nil {
+			t.Fatalf("expected no error, got %s", err)
+		}
+	}
+
+	t.Log("TOML")
+	{
+		viper.Set(KeyGenerateConfig, "toml")
+		err := GenerateConfig(ioutil.Discard)
+		if err != nil {
+			t.Fatalf("expected no error, got %s", err)
+		}
+	}
+
+	t.Log("JSON")
+	{
+		viper.Set(KeyGenerateConfig, "json")
+		err := GenerateConfig(ioutil.Discard)
+		if err != nil {
+			t.Fatalf("expected no error, got %s", err)
+		}
+	}
+}
+
 func TestGetConfig(t *testing.T) {
 	t.Log("Testing getConfig")
 	zerolog.SetGlobalLevel(zerolog.Disabled)