rsc minikube dashboard subcommand

minikube will open default browser and navigate to Kubernetes UI when run minikube dashboard.
Or just print url of Kubernetes UI if run minikube dashboard --url.

Before doing dashboard, minikube checks local cluster’s status, which uses below’s pkgs:

• minikube/pkg/minikube/machine
• minikube/pkg/minikube/cluster

First, new a machine client api, client api is a struct which has certsDir、 storePath and libmachine.API.
Second cluster pkg checks if local cluster is running by cluster.EnsureMinikubeRunningOrExit(api, 1).

In dashboard subcommand, minikube will retry 20 times to CheckService:

if err = commonutil.RetryAfter(20, func() error { return service.CheckService(namespace, svc) }, 6*time.Second); err != nil {
    fmt.Fprintf(os.Stderr, "Could not find finalized endpoint being pointed to by %s: %s\n", svc, err)
    os.Exit(1)
}

Let’s dive into the commonutil.RetryAfter function:

func RetryAfter(attempts int, callback func() error, d time.Duration) (err error) {
	m := MultiError{}
	for i := 0; i < attempts; i++ {
		err = callback()
		if err == nil {
			return nil
		}
		m.Collect(err)
		if _, ok := err.(*RetriableError); !ok {
			return m.ToError()
		}
		time.Sleep(d)
	}
	return m.ToError()
}

Beyond my exception, RetryAfter function is simple. It uses for-loop. In each loop,it runs callback function, if runs into error, handles it.

MultiError is a wrapper of golang error type, in ToError(), MultiError ranges its errors and join error strings together:

return errors.New(strings.Join(errStrings, "\n"))

Because each invoke of minikube dashboard is sync, so we do not meet high-currency challenge.

For operating browser, minikube uses browser pkg.