// still alive. As ztunnel shouldn't send anything unless we send
			// something first, we expect to get an os.ErrDeadlineExceeded error
			// here if the connection is still alive.
			// note that unlike tcp connections, reading is a good enough test here.
			_, err := conn.readMessage(time.Second / 100)
			switch {
			case !errors.Is(err, os.ErrDeadlineExceeded):
				log.Debugf("ztunnel keepalive failed: %v", err)

  // It is provided as a write-only input field for convenience.
  // All keys and values are merged into the data field on write, overwriting any existing values.
  // The stringData field is never output when reading from the API.
  // +k8s:conversion-gen=false
  // +optional
  map<string, string> stringData = 4;

  // Used to facilitate programmatic handling of secret data.

# Controllers

Istio has a variety of [controllers](https://kubernetes.io/docs/concepts/architecture/controller/), which basically watch some inputs and do something.
This can be reading from Kubernetes and writing other objects back, writing to proxies over XDS, etc.

Unfortunately, writing controllers is very error prone, even for seemingly simple cases.
To work around this, Istio has a variety of abstractions meant to make writing controllers easier.

## Clients

	viper.SetConfigName(configName)
	viper.SetConfigType(configType)
	viper.AddConfigPath(configPath)
	viper.SetEnvKeyReplacer(strings.NewReplacer("-", "_"))
	err := viper.ReadInConfig()
	// Ignore errors reading the configuration unless the file is explicitly customized
	if root.IstioConfig != defaultIstioctlConfig {
		return err
	}

	return nil
}

func init() {

```mermaid
graph TD
    subgraph ConfigStore
        xcs(XDS Client)
        ccs(CRD Client)
        fcs(Filesystem Client)
        acs(Aggregate)

the policy propagation from Istiod to Envoy and the final AuthorizationPolicy list merged
from multiple sources (mesh-level, namespace-level and workload-level).

The command also supports reading from a standalone config dump file with flag -f.`,
		Example: `  # Check AuthorizationPolicy applied to pod httpbin-88ddbcfdd-nt5jb:
  istioctl x authz check httpbin-88ddbcfdd-nt5jb

  // singularResource is the singular name of the resource.  This allows clients to handle plural and singular opaquely.
  // For many clients the singular form of the resource will be more understandable to users reading messages and should be used when integrating the name of the resource into a sentence.
  // The command line tool kubectl, for example, allows use of the singular resource name in place of plurals.

	for _, f := range args {
		var r *os.File

		// Handle "-" as stdin as a special case.
		if f == "-" {
			if isatty.IsTerminal(os.Stdin.Fd()) && !isJSONorYAMLOutputFormat() {
				fmt.Fprint(cmd.OutOrStdout(), "Reading from stdin:\n")
			}
			r = os.Stdin
			readers = append(readers, local.ReaderSource{Name: f, Reader: r})
			continue
		}

		fi, err := os.Stat(f)
		if err != nil {
			return nil, err
		}