Add exitOnWait flag

This enables the exitOnWait behavior from the commandline so most
users don't need to define two different config files.

Signed-off-by: Kevin Fox <[email protected]>

README.md

@@ -13,6 +13,8 @@ The SPIFFE Helper is a simple utility for fetching X.509 SVID certificates from
 
 If `-config` is not specified, the default value `helper.conf` is assumed. 
 
+The flag `-exitWhenReady` is also supported.
+
 ## Configuration
 The configuration file is an [HCL](https://github.com/hashicorp/hcl) formatted file that defines the following configurations:
 

cmd/spiffe-helper/main.go

@@ -17,24 +17,25 @@ func main() {
 	// 2. Run Sidecar's Daemon
 
 	configFile := flag.String("config", "helper.conf", "<configFile> Configuration file path")
+	exitWhenReady := flag.Bool("exitWhenReady", false, "Exit once the requested objects are retrieved")
 	flag.Parse()
 
 	log := logrus.WithField("system", "spiffe-helper")
 	log.Infof("Using configuration file: %q\n", *configFile)
 
-	if err := startSidecar(*configFile, log); err != nil {
+	if err := startSidecar(*configFile, *exitWhenReady, log); err != nil {
 		log.WithError(err).Error("Exiting due this error")
 		os.Exit(1)
 	}
 
 	log.Infof("Exiting")
 }
 
-func startSidecar(configPath string, log logrus.FieldLogger) error {
+func startSidecar(configPath string, exitWhenReady bool, log logrus.FieldLogger) error {
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
 	defer stop()
 
-	spiffeSidecar, err := sidecar.New(configPath, log)
+	spiffeSidecar, err := sidecar.New(configPath, exitWhenReady, log)
 	if err != nil {
 		return fmt.Errorf("Failed to create sidecar: %w", err)
 	}

pkg/sidecar/sidecar.go

@@ -41,7 +41,7 @@ type Sidecar struct {
 }
 
 // New creates a new SPIFFE sidecar
-func New(configPath string, log logrus.FieldLogger) (*Sidecar, error) {
+func New(configPath string, exitWhenReady bool, log logrus.FieldLogger) (*Sidecar, error) {
 	config, err := ParseConfig(configPath)
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse %q: %w", configPath, err)
@@ -68,6 +68,8 @@ func New(configPath string, log logrus.FieldLogger) (*Sidecar, error) {
 		config.Log.Warn("No cmd defined to execute.")
 	}
 
+	config.ExitWhenReady = config.ExitWhenReady || exitWhenReady
+
 	return &Sidecar{
 		config:        config,
 		certReadyChan: make(chan struct{}, 1),