Add example for nginx custom error pages

images/custom-error-pages/main.go

@@ -0,0 +1,94 @@
+/*
+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 (
+	"fmt"
+	"io"
+	"log"
+	"mime"
+	"net/http"
+	"os"
+	"strconv"
+)
+
+const (
+	FormatHeader = "X-Format"
+
+	CodeHeader = "X-Code"
+
+	ContentType = "Content-Type"
+)
+
+func main() {
+	path := "/www"
+	if os.Getenv("PATH") != "" {
+		path = os.Getenv("PATH")
+	}
+	http.HandleFunc("/", errorHandler(path))
+	http.ListenAndServe(fmt.Sprintf(":8080"), nil)
+}
+
+func errorHandler(path string) func(http.ResponseWriter, *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		ext := "html"
+
+		format := r.Header.Get(FormatHeader)
+		if format == "" {
+			format = "text/html"
+			log.Printf("forma not specified. Using %v\n", format)
+		}
+
+		mediaType, _, _ := mime.ParseMediaType(format)
+		cext, err := mime.ExtensionsByType(mediaType)
+		if err != nil {
+			log.Printf("unexpected error reading media type extension: %v. Using %v\n", err, ext)
+		} else {
+			ext = cext[0]
+		}
+		w.Header().Set(ContentType, format)
+
+		errCode := r.Header.Get(CodeHeader)
+		code, err := strconv.Atoi(errCode)
+		if err != nil {
+			code = 404
+			log.Printf("unexpected error reading return code: %v. Using %v\n", err, code)
+		}
+		w.WriteHeader(code)
+
+		file := fmt.Sprintf("%v/%v%v", path, code, ext)
+		f, err := os.Open(file)
+		if err != nil {
+			log.Printf("unexpected error opening file: %v\n", err)
+			scode := strconv.Itoa(code)
+			file := fmt.Sprintf("%v/%cxx%v", path, scode[0], ext)
+			f, err := os.Open(file)
+			if err != nil {
+				log.Printf("unexpected error opening file: %v\n", err)
+				http.NotFound(w, r)
+				return
+			}
+			defer f.Close()
+			log.Printf("serving custom error response for code %v and format %v from file %v\n", code, format, file)
+			io.Copy(w, f)
+			return
+		}
+		defer f.Close()
+		log.Printf("serving custom error response for code %v and format %v from file %v\n", code, format, file)
+		io.Copy(w, f)
+	}
+}