Add godoc to pkg/util/configz.

Document the intended use of this package. In particular, document the
fact that it is intended for ComponentConfig.

hack/.golint_failures

@@ -359,7 +359,6 @@ pkg/serviceaccount
 pkg/ssh
 pkg/util/bandwidth
 pkg/util/config
-pkg/util/configz
 pkg/util/ebtables
 pkg/util/env
 pkg/util/file

pkg/util/configz/configz.go

@@ -14,6 +14,29 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+// Package configz serves ComponentConfig objects from running components.
+//
+// Each component that wants to serve its ComponentConfig creates a Config
+// object, and the program should call InstallHandler once. e.g.,
+//  func main() {
+//  	boatConfig := getBoatConfig()
+//  	planeConfig := getPlaneConfig()
+//
+//  	bcz, err := configz.New("boat")
+//  	if err != nil {
+//  		panic(err)
+//  	}
+//  	bcz.Set(boatConfig)
+//
+//  	pcz, err := configz.New("plane")
+//  	if err != nil {
+//  		panic(err)
+//  	}
+//  	pcz.Set(planeConfig)
+//
+//  	configz.InstallHandler(http.DefaultServeMux)
+//  	http.ListenAndServe(":8080", http.DefaultServeMux)
+//  }
 package configz
 
 import (
@@ -28,10 +51,14 @@ var (
 	configs      = map[string]*Config{}
 )
 
+// Config is a handle to a ComponentConfig object. Don't create these directly;
+// use New() instead.
 type Config struct {
 	val interface{}
 }
 
+// InstallHandler adds an HTTP handler on the given mux for the "/configz"
+// endpoint which serves all registered ComponentConfigs in JSON format.
 func InstallHandler(m mux) {
 	m.Handle("/configz", http.HandlerFunc(handle))
 }
@@ -40,6 +67,8 @@ type mux interface {
 	Handle(string, http.Handler)
 }
 
+// New creates a Config object with the given name. Each Config is registered
+// with this package's "/configz" handler.
 func New(name string) (*Config, error) {
 	configsGuard.Lock()
 	defer configsGuard.Unlock()
@@ -51,18 +80,22 @@ func New(name string) (*Config, error) {
 	return &newConfig, nil
 }
 
+// Delete removes the named ComponentConfig from this package's "/configz"
+// handler.
 func Delete(name string) {
 	configsGuard.Lock()
 	defer configsGuard.Unlock()
 	delete(configs, name)
 }
 
+// Set sets the ComponentConfig for this Config.
 func (v *Config) Set(val interface{}) {
 	configsGuard.Lock()
 	defer configsGuard.Unlock()
 	v.val = val
 }
 
+// MarshalJSON marshals the ComponentConfig as JSON data.
 func (v *Config) MarshalJSON() ([]byte, error) {
 	return json.Marshal(v.val)
 }