Created
July 3, 2019 11:50
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Some changes in https://github.com/golang/go/issues/29162#issuecomment-445888885
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package main | |
import ( | |
"bufio" | |
"bytes" | |
"compress/gzip" | |
"crypto/tls" | |
"fmt" | |
"io" | |
"io/ioutil" | |
"log" | |
"net" | |
"net/http" | |
"net/http/httptest" | |
"net/textproto" | |
"strings" | |
"time" | |
) | |
func main() { | |
getResponseWithCustomClient() | |
getWithDefaultClient() | |
} | |
func healthCheckHandler(w http.ResponseWriter, r *http.Request) { | |
w.Header().Set("Content-Type", "application/json") | |
encoding := r.Header.Get("Accept-Encoding") | |
if strings.Contains(encoding, "gzip") { | |
encoder, _ := gzip.NewWriterLevel(w, 6) | |
encodingName := "gzip" | |
w.Header().Set("Transfer-Encoding", encodingName ) | |
w.Header().Set("Accept-Encoding", encodingName) | |
w.Header().Add("Vary", "Accept-Encoding") | |
fmt.Fprint(encoder, `{"alive": true, "query": "`+r.URL.RawQuery+`"}`) | |
} else { | |
fmt.Fprint(w, `{"alive": true, "query": "`+r.URL.RawQuery+`"}`) | |
} | |
} | |
// Test to check if the server will exit gracefully when client exits | |
func getWithDefaultClient() { | |
handler := http.HandlerFunc(healthCheckHandler) | |
server := httptest.NewServer(handler) | |
defer server.Close() | |
serverURL := server.URL + "?test=true" | |
req, err := http.NewRequest("GET", serverURL, nil) | |
if err != nil { | |
log.Println("http request error", err.Error()) | |
return | |
} | |
req.Header.Set("Accept-Encoding", "gzip") | |
res, err := http.DefaultClient.Do(req) | |
if err != nil && !strings.Contains(err.Error(), "context canceled") { | |
log.Println("http client error", err.Error()) | |
return | |
} | |
contents, err := ioutil.ReadAll(res.Body) | |
fmt.Println("response", string(contents)) | |
} | |
func getResponseWithCustomClient() { | |
handler := http.HandlerFunc(healthCheckHandler) | |
server := httptest.NewServer(handler) | |
defer server.Close() | |
serverURL := server.URL + "?test=true" | |
req, err := http.NewRequest("GET", serverURL, nil) | |
if err != nil { | |
log.Println("http request error", err.Error()) | |
return | |
} | |
req.Header.Set("Accept-Encoding", "gzip") | |
netClient := &http.Client{ | |
Timeout: time.Second * 10, | |
Transport: &transferEncodingRedactor{base: http.DefaultTransport.(*http.Transport)}, | |
} | |
res, err := netClient.Do(req) | |
if err != nil && !strings.Contains(err.Error(), "context canceled") { | |
log.Println("http client error", err.Error()) | |
return | |
} | |
contents, err := ioutil.ReadAll(res.Body) | |
fmt.Println("response", string(contents)) | |
} | |
type transferEncodingRedactor struct { | |
base *http.Transport | |
} | |
func (rt *transferEncodingRedactor) RoundTrip(req *http.Request) (*http.Response, error) { | |
// Optimistic route i.e common case. | |
res, err := rt.base.RoundTrip(req) | |
if err == nil || res != nil { | |
return res, err | |
} | |
// An error occured here but now time ot examine the contents | |
if !strings.Contains(err.Error(), "unsupported transfer encoding") { | |
return res, err | |
} | |
u := req.URL | |
var conn net.Conn | |
switch req.URL.Scheme { | |
case "https": | |
tr := rt.base | |
if tr == nil { | |
tr = http.DefaultTransport.(*http.Transport) | |
} | |
host := req.URL.Host | |
if !strings.Contains(host, ":") { | |
host += ":443" | |
} | |
conn, err = tls.Dial("tcp", host, tr.TLSClientConfig) | |
default: | |
host := req.URL.Host | |
if !strings.Contains(host, ":") { | |
host += ":80" | |
} | |
conn, err = net.Dial("tcp", host) | |
} | |
if err != nil { | |
return nil, fmt.Errorf("dial error: %v", err) | |
} | |
// Ensure we close the connection after. | |
// Perhaps you might want to reuse it per host? | |
defer conn.Close() | |
s := u.Path | |
if q := u.RawQuery; len(q) > 0 { | |
s += "?" + q | |
} | |
intro := fmt.Sprintf("%s /%s HTTP/1.1\r\nHost:%s\r\n\r\n", req.Method, s, u.Host) | |
fmt.Fprint(conn, intro) | |
br := bufio.NewReader(conn) | |
// And now we've got the case of an unsupported transfer | |
// encoding time for a raw fetch and header rewrite. | |
tp := textproto.NewReader(br) | |
protoLine, err := tp.ReadLine() | |
if err != nil { | |
return nil, fmt.Errorf("ReadLine error: %v", err) | |
} | |
// Time to parse the headers | |
rhdr, err := tp.ReadMIMEHeader() | |
if err != nil { | |
return nil, fmt.Errorf("ReadMIMEHeader: %v", err) | |
} | |
hdr := http.Header(rhdr) | |
// Now rewrite the header | |
if te := hdr.Get("Transfer-Encoding"); te == "gzip" { | |
hdr.Set("Content-Encoding", "gzip") | |
delete(hdr, "Transfer-Encoding") | |
} | |
// After this rewrite, reassemble the already read parts back | |
// and then get them to ReadResponse | |
hdrBuf := new(bytes.Buffer) | |
if err := hdr.Write(hdrBuf); err != nil { | |
return nil, fmt.Errorf("Rewriting header to wire: %v", err) | |
} | |
reconstructed := io.MultiReader(strings.NewReader(protoLine+"\r\n"), hdrBuf, strings.NewReader("\r\n"), br) | |
return http.ReadResponse(bufio.NewReader(reconstructed), req) | |
} | |
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