update static pages, dockerfile and add license info

Dockerfile

@@ -26,4 +26,4 @@ COPY --from=build /go/src/github.com/raspbernetes/custom-error-pages .
 
 USER nonroot:nonroot
 
-ENTRYPOINT ["/custom-error-pages"]
+ENTRYPOINT ["/custom-error-pages"]

main.go

@@ -1,3 +1,19 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 package main
 
 import (
@@ -10,7 +26,7 @@ import (
 	"strconv"
 	"strings"
 	"time"
-
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
@@ -45,31 +61,51 @@ const (
 	// ErrFilesPathVar is the name of the environment variable indicating
 	// the location on disk of files served by the handler.
 	ErrFilesPathVar = "ERROR_FILES_PATH"
+
+	// DefaultFormatVar is the name of the environment variable indicating
+	// the default error MIME type that should be returned if either the
+	// client does not specify an Accept header, or the Accept header provided
+	// cannot be mapped to a file extension.
+	DefaultFormatVar = "DEFAULT_RESPONSE_FORMAT"
 )
 
+func init() {
+	prometheus.MustRegister(requestCount)
+	prometheus.MustRegister(requestDuration)
+}
+
 func main() {
-	errFilesPath := "./pages"
+	errFilesPath := "/www"
 	if os.Getenv(ErrFilesPathVar) != "" {
 		errFilesPath = os.Getenv(ErrFilesPathVar)
 	}
 
-	http.HandleFunc("/", errorHandler(errFilesPath))
+	defaultFormat := "text/html"
+	if os.Getenv(DefaultFormatVar) != "" {
+		defaultFormat = os.Getenv(DefaultFormatVar)
+	}
+
+	http.HandleFunc("/", errorHandler(errFilesPath, defaultFormat))
 
 	http.Handle("/metrics", promhttp.Handler())
 
 	http.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusOK)
-		w.Write([]byte("OK"))
-		fmt.Fprint(w)
 	})
 
 	http.ListenAndServe(fmt.Sprintf(":8080"), nil)
 }
 
-func errorHandler(path string) func(http.ResponseWriter, *http.Request) {
+func errorHandler(path, defaultFormat string) func(http.ResponseWriter, *http.Request) {
+	defaultExts, err := mime.ExtensionsByType(defaultFormat)
+	if err != nil || len(defaultExts) == 0 {
+		panic("couldn't get file extension for default format")
+	}
+	defaultExt := defaultExts[0]
+
 	return func(w http.ResponseWriter, r *http.Request) {
 		start := time.Now()
-		ext := "html"
+		ext := defaultExt
 
 		if os.Getenv("DEBUG") != "" {
 			w.Header().Set(FormatHeader, r.Header.Get(FormatHeader))
@@ -85,14 +121,14 @@ func errorHandler(path string) func(http.ResponseWriter, *http.Request) {
 
 		format := r.Header.Get(FormatHeader)
 		if format == "" {
-			format = "text/html"
+			format = defaultFormat
 			log.Printf("format not specified. Using %v", format)
 		}
 
 		cext, err := mime.ExtensionsByType(format)
 		if err != nil {
 			log.Printf("unexpected error reading media type extension: %v. Using %v", err, ext)
-			format = "text/html"
+			format = defaultFormat
 		} else if len(cext) == 0 {
 			log.Printf("couldn't get media type extension. Using %v", ext)
 		} else {
@@ -111,6 +147,10 @@ func errorHandler(path string) func(http.ResponseWriter, *http.Request) {
 		if !strings.HasPrefix(ext, ".") {
 			ext = "." + ext
 		}
+		// special case for compatibility
+		if ext == ".htm" {
+			ext = ".html"
+		}
 		file := fmt.Sprintf("%v/%v%v", path, code, ext)
 		f, err := os.Open(file)
 		if err != nil {

metrics.go

@@ -1,3 +1,19 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 // Collect and display prometheus metrics
 
 package main

www/401.json

@@ -0,0 +1 @@
+{ "message": "You do not have permission to perform this request" }

www/404.json

@@ -0,0 +1 @@
+{ "message": "The page you're looking for could not be found" }

www/500.json

@@ -0,0 +1 @@
+{ "message": "An internal server error has been occured" }

www/503.json

@@ -0,0 +1 @@
+{ "message": "The server is temporarily unavailable due maintenance" }