traefik/middlewares/errorpages/error_pages.go

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package errorpages
import (
"bufio"
"bytes"
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"errors"
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"fmt"
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"net"
"net/http"
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"net/url"
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"strconv"
"strings"
"github.com/containous/traefik/log"
"github.com/containous/traefik/middlewares"
"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 _ middlewares.Stateful = &responseRecorderWithCloseNotify{}
// Handler is a middleware that provides the custom error pages
type Handler struct {
BackendName string
backendHandler http.Handler
httpCodeRanges types.HTTPCodeRanges
backendURL string
backendQuery string
FallbackURL string // Deprecated
}
// NewHandler initializes the utils.ErrorHandler for the custom error pages
func NewHandler(errorPage *types.ErrorPage, backendName string) (*Handler, error) {
if len(backendName) == 0 {
return nil, errors.New("error pages: backend name is mandatory ")
}
httpCodeRanges, err := types.NewHTTPCodeRanges(errorPage.Status)
if err != nil {
return nil, err
}
return &Handler{
BackendName: backendName,
httpCodeRanges: httpCodeRanges,
backendQuery: errorPage.Query,
backendURL: "http://0.0.0.0",
}, nil
}
// PostLoad adds backend handler if available
func (h *Handler) PostLoad(backendHandler http.Handler) error {
if backendHandler == nil {
fwd, err := forward.New()
if err != nil {
return err
}
h.backendHandler = fwd
h.backendURL = h.FallbackURL
} else {
h.backendHandler = backendHandler
}
return nil
}
func (h *Handler) ServeHTTP(w http.ResponseWriter, req *http.Request, next http.HandlerFunc) {
if h.backendHandler == nil {
log.Error("Error pages: no backend handler.")
next.ServeHTTP(w, req)
return
}
recorder := newResponseRecorder(w)
next.ServeHTTP(recorder, req)
// check the recorder code against the configured http status code ranges
for _, block := range h.httpCodeRanges {
if recorder.GetCode() >= block[0] && recorder.GetCode() <= block[1] {
log.Errorf("Caught HTTP Status Code %d, returning error page", recorder.GetCode())
var query string
if len(h.backendQuery) > 0 {
query = "/" + strings.TrimPrefix(h.backendQuery, "/")
query = strings.Replace(query, "{status}", strconv.Itoa(recorder.GetCode()), -1)
}
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pageReq, err := newRequest(h.backendURL + query)
if err != nil {
log.Error(err)
w.WriteHeader(recorder.GetCode())
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fmt.Fprint(w, http.StatusText(recorder.GetCode()))
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return
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}
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recorderErrorPage := newResponseRecorder(w)
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utils.CopyHeaders(pageReq.Header, req.Header)
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h.backendHandler.ServeHTTP(recorderErrorPage, pageReq.WithContext(req.Context()))
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utils.CopyHeaders(w.Header(), recorder.Header())
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for key := range recorderErrorPage.Header() {
w.Header().Del(key)
}
utils.CopyHeaders(w.Header(), recorderErrorPage.Header())
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w.WriteHeader(recorder.GetCode())
w.Write(recorderErrorPage.GetBody().Bytes())
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return
}
}
// did not catch a configured status code so proceed with the request
utils.CopyHeaders(w.Header(), recorder.Header())
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w.WriteHeader(recorder.GetCode())
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w.Write(recorder.GetBody().Bytes())
}
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func newRequest(baseURL string) (*http.Request, error) {
u, err := url.Parse(baseURL)
if err != nil {
return nil, fmt.Errorf("error pages: error when parse URL: %v", err)
}
req, err := http.NewRequest(http.MethodGet, u.String(), nil)
if err != nil {
return nil, fmt.Errorf("error pages: error when create query: %v", err)
}
req.RequestURI = u.RequestURI()
return req, nil
}
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type responseRecorder interface {
http.ResponseWriter
http.Flusher
GetCode() int
GetBody() *bytes.Buffer
IsStreamingResponseStarted() bool
}
// newResponseRecorder returns an initialized responseRecorder.
func newResponseRecorder(rw http.ResponseWriter) responseRecorder {
recorder := &responseRecorderWithoutCloseNotify{
HeaderMap: make(http.Header),
Body: new(bytes.Buffer),
Code: http.StatusOK,
responseWriter: rw,
}
if _, ok := rw.(http.CloseNotifier); ok {
return &responseRecorderWithCloseNotify{recorder}
}
return recorder
}
// responseRecorderWithoutCloseNotify is an implementation of http.ResponseWriter that
// records its mutations for later inspection.
type responseRecorderWithoutCloseNotify 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 responseRecorderWithCloseNotify struct {
*responseRecorderWithoutCloseNotify
}
// CloseNotify returns a channel that receives at most a
// single value (true) when the client connection has gone away.
func (rw *responseRecorderWithCloseNotify) CloseNotify() <-chan bool {
return rw.responseWriter.(http.CloseNotifier).CloseNotify()
}
// Header returns the response headers.
func (rw *responseRecorderWithoutCloseNotify) Header() http.Header {
if rw.HeaderMap == nil {
rw.HeaderMap = make(http.Header)
}
return rw.HeaderMap
}
func (rw *responseRecorderWithoutCloseNotify) GetCode() int {
return rw.Code
}
func (rw *responseRecorderWithoutCloseNotify) GetBody() *bytes.Buffer {
return rw.Body
}
func (rw *responseRecorderWithoutCloseNotify) IsStreamingResponseStarted() bool {
return rw.streamingResponseStarted
}
// Write always succeeds and writes to rw.Body, if not nil.
func (rw *responseRecorderWithoutCloseNotify) Write(buf []byte) (int, error) {
if rw.err != nil {
return 0, rw.err
}
return rw.Body.Write(buf)
}
// WriteHeader sets rw.Code.
func (rw *responseRecorderWithoutCloseNotify) WriteHeader(code int) {
rw.Code = code
}
// Hijack hijacks the connection
func (rw *responseRecorderWithoutCloseNotify) Hijack() (net.Conn, *bufio.ReadWriter, error) {
return rw.responseWriter.(http.Hijacker).Hijack()
}
// Flush sends any buffered data to the client.
func (rw *responseRecorderWithoutCloseNotify) 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()
if flusher, ok := rw.responseWriter.(http.Flusher); ok {
flusher.Flush()
}
}