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Merge pull request #71413 from liggitt/backend-error-1.12

Cherry pick of #71412: Handle error responses from backends
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k8s-ci-robot committed Nov 26, 2018
2 parents 4be525c + 774585f commit 435f92c719f279a3a67808c80521ea17d5715c66
Showing with 37 additions and 0 deletions.
  1. +37 −0 staging/src/
@@ -17,6 +17,7 @@ limitations under the License.
package proxy
import (
@@ -271,6 +272,18 @@ func (h *UpgradeAwareHandler) tryUpgrade(w http.ResponseWriter, req *http.Reques
defer backendConn.Close()
// determine the http response code from the backend by reading from rawResponse+backendConn
rawResponseCode, headerBytes, err := getResponseCode(io.MultiReader(bytes.NewReader(rawResponse), backendConn))
if err != nil {
glog.V(6).Infof("Proxy connection error: %v", err)
h.Responder.Error(w, req, err)
return true
if len(headerBytes) > len(rawResponse) {
// we read beyond the bytes stored in rawResponse, update rawResponse to the full set of bytes read from the backend
rawResponse = headerBytes
// Once the connection is hijacked, the ErrorResponder will no longer work, so
// hijacking should be the last step in the upgrade.
requestHijacker, ok := w.(http.Hijacker)
@@ -295,6 +308,17 @@ func (h *UpgradeAwareHandler) tryUpgrade(w http.ResponseWriter, req *http.Reques
if rawResponseCode != http.StatusSwitchingProtocols {
// If the backend did not upgrade the request, finish echoing the response from the backend to the client and return, closing the connection.
glog.V(6).Infof("Proxy upgrade error, status code %d", rawResponseCode)
_, err := io.Copy(requestHijackedConn, backendConn)
if err != nil && !strings.Contains(err.Error(), "use of closed network connection") {
glog.Errorf("Error proxying data from backend to client: %v", err)
// Indicate we handled the request
return true
// Proxy the connection. This is bidirectional, so we need a goroutine
// to copy in each direction. Once one side of the connection exits, we
// exit the function which performs cleanup and in the process closes
@@ -356,6 +380,19 @@ func (h *UpgradeAwareHandler) DialForUpgrade(req *http.Request) (net.Conn, error
return dial(updatedReq, h.UpgradeTransport)
// getResponseCode reads a http response from the given reader, returns the status code,
// the bytes read from the reader, and any error encountered
func getResponseCode(r io.Reader) (int, []byte, error) {
rawResponse := bytes.NewBuffer(make([]byte, 0, 256))
// Save the bytes read while reading the response headers into the rawResponse buffer
resp, err := http.ReadResponse(bufio.NewReader(io.TeeReader(r, rawResponse)), nil)
if err != nil {
return 0, nil, err
// return the http status code and the raw bytes consumed from the reader in the process
return resp.StatusCode, rawResponse.Bytes(), nil
// dial dials the backend at req.URL and writes req to it.
func dial(req *http.Request, transport http.RoundTripper) (net.Conn, error) {
conn, err := DialURL(req.Context(), req.URL, transport)

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