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main.go
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main.go
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/*
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"
"strings"
"time"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
const (
// FormatHeader name of the header used to extract the format
FormatHeader = "X-Format"
// CodeHeader name of the header used as source of the HTTP statu code to return
CodeHeader = "X-Code"
// ContentType name of the header that defines the format of the reply
ContentType = "Content-Type"
// OriginalURI name of the header with the original URL from NGINX
OriginalURI = "X-Original-URI"
// Namespace name of the header that contains information about the Ingress namespace
Namespace = "X-Namespace"
// IngressName name of the header that contains the matched Ingress
IngressName = "X-Ingress-Name"
// ServiceName name of the header that contains the matched Service in the Ingress
ServiceName = "X-Service-Name"
// ServicePort name of the header that contains the matched Service port in the Ingress
ServicePort = "X-Service-Port"
// ErrFilesPathVar is the name of the environment variable indicating
// the location on disk of files served by the handler.
ErrFilesPathVar = "ERROR_FILES_PATH"
)
func main() {
errFilesPath := "/www"
if os.Getenv(ErrFilesPathVar) != "" {
errFilesPath = os.Getenv(ErrFilesPathVar)
}
http.HandleFunc("/", errorHandler(errFilesPath))
http.Handle("/metrics", promhttp.Handler())
http.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(http.StatusOK)
})
http.ListenAndServe(fmt.Sprintf(":8080"), nil)
}
func errorHandler(path string) func(http.ResponseWriter, *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
start := time.Now()
ext := "html"
if os.Getenv("DEBUG") != "" {
w.Header().Set(FormatHeader, r.Header.Get(FormatHeader))
w.Header().Set(CodeHeader, r.Header.Get(CodeHeader))
w.Header().Set(ContentType, r.Header.Get(ContentType))
w.Header().Set(OriginalURI, r.Header.Get(OriginalURI))
w.Header().Set(Namespace, r.Header.Get(Namespace))
w.Header().Set(IngressName, r.Header.Get(IngressName))
w.Header().Set(ServiceName, r.Header.Get(ServiceName))
w.Header().Set(ServicePort, r.Header.Get(ServicePort))
}
format := r.Header.Get(FormatHeader)
if format == "" {
format = "text/html"
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)
} else if len(cext) == 0 {
log.Printf("couldn't get media type extension. Using %v", 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", err, code)
}
w.WriteHeader(code)
if !strings.HasPrefix(ext, ".") {
ext = "." + ext
}
file := fmt.Sprintf("%v/%v%v", path, code, ext)
f, err := os.Open(file)
if err != nil {
log.Printf("unexpected error opening file: %v", 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", err)
http.NotFound(w, r)
return
}
defer f.Close()
log.Printf("serving custom error response for code %v and format %v from file %v", 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", code, format, file)
io.Copy(w, f)
duration := time.Now().Sub(start).Seconds()
proto := strconv.Itoa(r.ProtoMajor)
proto = fmt.Sprintf("%s.%s", proto, strconv.Itoa(r.ProtoMinor))
requestCount.WithLabelValues(proto).Inc()
requestDuration.WithLabelValues(proto).Observe(duration)
}
}