traefik/middlewares/error_pages.go

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package middlewares
import (
"bufio"
"bytes"
"net"
"net/http"
"strconv"
"strings"
"github.com/containous/traefik/log"
"github.com/containous/traefik/types"
"github.com/vulcand/oxy/forward"
"github.com/vulcand/oxy/utils"
)
// Compile time validation that the response recorder implements http interfaces correctly.
var _ Stateful = &errorPagesResponseRecorderWithCloseNotify{}
//ErrorPagesHandler is a middleware that provides the custom error pages
type ErrorPagesHandler struct {
HTTPCodeRanges [][2]int
BackendURL string
errorPageForwarder *forward.Forwarder
}
//NewErrorPagesHandler initializes the utils.ErrorHandler for the custom error pages
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func NewErrorPagesHandler(errorPage *types.ErrorPage, backendURL string) (*ErrorPagesHandler, error) {
fwd, err := forward.New()
if err != nil {
return nil, err
}
//Break out the http status code ranges into a low int and high int
//for ease of use at runtime
var blocks [][2]int
for _, block := range errorPage.Status {
codes := strings.Split(block, "-")
//if only a single HTTP code was configured, assume the best and create the correct configuration on the user's behalf
if len(codes) == 1 {
codes = append(codes, codes[0])
}
lowCode, err := strconv.Atoi(codes[0])
if err != nil {
return nil, err
}
highCode, err := strconv.Atoi(codes[1])
if err != nil {
return nil, err
}
blocks = append(blocks, [2]int{lowCode, highCode})
}
return &ErrorPagesHandler{
HTTPCodeRanges: blocks,
BackendURL: backendURL + errorPage.Query,
errorPageForwarder: fwd},
nil
}
func (ep *ErrorPagesHandler) ServeHTTP(w http.ResponseWriter, req *http.Request, next http.HandlerFunc) {
recorder := newErrorPagesResponseRecorder(w)
next.ServeHTTP(recorder, req)
w.WriteHeader(recorder.GetCode())
//check the recorder code against the configured http status code ranges
for _, block := range ep.HTTPCodeRanges {
if recorder.GetCode() >= block[0] && recorder.GetCode() <= block[1] {
log.Errorf("Caught HTTP Status Code %d, returning error page", recorder.GetCode())
finalURL := strings.Replace(ep.BackendURL, "{status}", strconv.Itoa(recorder.GetCode()), -1)
if newReq, err := http.NewRequest(http.MethodGet, finalURL, nil); err != nil {
w.Write([]byte(http.StatusText(recorder.GetCode())))
} else {
ep.errorPageForwarder.ServeHTTP(w, newReq)
}
return
}
}
//did not catch a configured status code so proceed with the request
utils.CopyHeaders(w.Header(), recorder.Header())
w.Write(recorder.GetBody().Bytes())
}
type errorPagesResponseRecorder interface {
http.ResponseWriter
http.Flusher
GetCode() int
GetBody() *bytes.Buffer
IsStreamingResponseStarted() bool
}
// newErrorPagesResponseRecorder returns an initialized responseRecorder.
func newErrorPagesResponseRecorder(rw http.ResponseWriter) errorPagesResponseRecorder {
recorder := &errorPagesResponseRecorderWithoutCloseNotify{
HeaderMap: make(http.Header),
Body: new(bytes.Buffer),
Code: http.StatusOK,
responseWriter: rw,
}
if _, ok := rw.(http.CloseNotifier); ok {
return &errorPagesResponseRecorderWithCloseNotify{recorder}
}
return recorder
}
// errorPagesResponseRecorderWithoutCloseNotify is an implementation of http.ResponseWriter that
// records its mutations for later inspection.
type errorPagesResponseRecorderWithoutCloseNotify struct {
Code int // the HTTP response code from WriteHeader
HeaderMap http.Header // the HTTP response headers
Body *bytes.Buffer // if non-nil, the bytes.Buffer to append written data to
responseWriter http.ResponseWriter
err error
streamingResponseStarted bool
}
type errorPagesResponseRecorderWithCloseNotify struct {
*errorPagesResponseRecorderWithoutCloseNotify
}
// CloseNotify returns a channel that receives at most a
// single value (true) when the client connection has gone
// away.
func (rw *errorPagesResponseRecorderWithCloseNotify) CloseNotify() <-chan bool {
return rw.responseWriter.(http.CloseNotifier).CloseNotify()
}
// Header returns the response headers.
func (rw *errorPagesResponseRecorderWithoutCloseNotify) Header() http.Header {
m := rw.HeaderMap
if m == nil {
m = make(http.Header)
rw.HeaderMap = m
}
return m
}
func (rw *errorPagesResponseRecorderWithoutCloseNotify) GetCode() int {
return rw.Code
}
func (rw *errorPagesResponseRecorderWithoutCloseNotify) GetBody() *bytes.Buffer {
return rw.Body
}
func (rw *errorPagesResponseRecorderWithoutCloseNotify) IsStreamingResponseStarted() bool {
return rw.streamingResponseStarted
}
// Write always succeeds and writes to rw.Body, if not nil.
func (rw *errorPagesResponseRecorderWithoutCloseNotify) Write(buf []byte) (int, error) {
if rw.err != nil {
return 0, rw.err
}
return rw.Body.Write(buf)
}
// WriteHeader sets rw.Code.
func (rw *errorPagesResponseRecorderWithoutCloseNotify) WriteHeader(code int) {
rw.Code = code
}
// Hijack hijacks the connection
func (rw *errorPagesResponseRecorderWithoutCloseNotify) Hijack() (net.Conn, *bufio.ReadWriter, error) {
return rw.responseWriter.(http.Hijacker).Hijack()
}
// Flush sends any buffered data to the client.
func (rw *errorPagesResponseRecorderWithoutCloseNotify) Flush() {
if !rw.streamingResponseStarted {
utils.CopyHeaders(rw.responseWriter.Header(), rw.Header())
rw.responseWriter.WriteHeader(rw.Code)
rw.streamingResponseStarted = true
}
_, err := rw.responseWriter.Write(rw.Body.Bytes())
if err != nil {
log.Errorf("Error writing response in responseRecorder: %s", err)
rw.err = err
}
rw.Body.Reset()
flusher, ok := rw.responseWriter.(http.Flusher)
if ok {
flusher.Flush()
}
}