Dynamic Configuration Refactoring

old/middlewares/errorpages/error_pages.go

@@ -0,0 +1,236 @@
+package errorpages
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"github.com/containous/traefik/old/log"
+	"github.com/containous/traefik/old/middlewares"
+	"github.com/containous/traefik/old/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)
+			}
+
+			pageReq, err := newRequest(h.backendURL + query)
+			if err != nil {
+				log.Error(err)
+				w.WriteHeader(recorder.GetCode())
+				fmt.Fprint(w, http.StatusText(recorder.GetCode()))
+				return
+			}
+
+			recorderErrorPage := newResponseRecorder(w)
+			utils.CopyHeaders(pageReq.Header, req.Header)
+
+			h.backendHandler.ServeHTTP(recorderErrorPage, pageReq.WithContext(req.Context()))
+
+			utils.CopyHeaders(w.Header(), recorderErrorPage.Header())
+			w.WriteHeader(recorder.GetCode())
+
+			if _, err = w.Write(recorderErrorPage.GetBody().Bytes()); err != nil {
+				log.Error(err)
+			}
+			return
+		}
+	}
+
+	// did not catch a configured status code so proceed with the request
+	utils.CopyHeaders(w.Header(), recorder.Header())
+	w.WriteHeader(recorder.GetCode())
+	w.Write(recorder.GetBody().Bytes())
+}
+
+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(), http.NoBody)
+	if err != nil {
+		return nil, fmt.Errorf("error pages: error when create query: %v", err)
+	}
+
+	req.RequestURI = u.RequestURI()
+	return req, nil
+}
+
+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 (r *responseRecorderWithCloseNotify) CloseNotify() <-chan bool {
+	return r.responseWriter.(http.CloseNotifier).CloseNotify()
+}
+
+// Header returns the response headers.
+func (r *responseRecorderWithoutCloseNotify) Header() http.Header {
+	if r.HeaderMap == nil {
+		r.HeaderMap = make(http.Header)
+	}
+
+	return r.HeaderMap
+}
+
+func (r *responseRecorderWithoutCloseNotify) GetCode() int {
+	return r.Code
+}
+
+func (r *responseRecorderWithoutCloseNotify) GetBody() *bytes.Buffer {
+	return r.Body
+}
+
+func (r *responseRecorderWithoutCloseNotify) IsStreamingResponseStarted() bool {
+	return r.streamingResponseStarted
+}
+
+// Write always succeeds and writes to rw.Body, if not nil.
+func (r *responseRecorderWithoutCloseNotify) Write(buf []byte) (int, error) {
+	if r.err != nil {
+		return 0, r.err
+	}
+	return r.Body.Write(buf)
+}
+
+// WriteHeader sets rw.Code.
+func (r *responseRecorderWithoutCloseNotify) WriteHeader(code int) {
+	r.Code = code
+}
+
+// Hijack hijacks the connection
+func (r *responseRecorderWithoutCloseNotify) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	return r.responseWriter.(http.Hijacker).Hijack()
+}
+
+// Flush sends any buffered data to the client.
+func (r *responseRecorderWithoutCloseNotify) Flush() {
+	if !r.streamingResponseStarted {
+		utils.CopyHeaders(r.responseWriter.Header(), r.Header())
+		r.responseWriter.WriteHeader(r.Code)
+		r.streamingResponseStarted = true
+	}
+
+	_, err := r.responseWriter.Write(r.Body.Bytes())
+	if err != nil {
+		log.Errorf("Error writing response in responseRecorder: %v", err)
+		r.err = err
+	}
+	r.Body.Reset()
+
+	if flusher, ok := r.responseWriter.(http.Flusher); ok {
+		flusher.Flush()
+	}
+}