diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go index 92d7f63af5..0e0731b08f 100644 --- a/src/net/http/httputil/reverseproxy.go +++ b/src/net/http/httputil/reverseproxy.go @@ -389,6 +389,11 @@ func (p *ReverseProxy) copyResponse(dst io.Writer, src io.Reader, flushInterval latency: flushInterval, } defer mlw.stop() + + // set up initial timer so headers get flushed even if body writes are delayed + mlw.flushPending = true + mlw.t = time.AfterFunc(flushInterval, mlw.delayedFlush) + dst = mlw } } diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go index 5edefa08e5..367ba73ae2 100644 --- a/src/net/http/httputil/reverseproxy_test.go +++ b/src/net/http/httputil/reverseproxy_test.go @@ -9,6 +9,7 @@ package httputil import ( "bufio" "bytes" + "context" "errors" "fmt" "io" @@ -317,6 +318,47 @@ func TestReverseProxyFlushInterval(t *testing.T) { } } +func TestReverseProxyFlushIntervalHeaders(t *testing.T) { + const expected = "hi" + stopCh := make(chan struct{}) + backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { + w.Header().Add("MyHeader", expected) + w.WriteHeader(200) + w.(http.Flusher).Flush() + <-stopCh + })) + defer backend.Close() + defer close(stopCh) + + backendURL, err := url.Parse(backend.URL) + if err != nil { + t.Fatal(err) + } + + proxyHandler := NewSingleHostReverseProxy(backendURL) + proxyHandler.FlushInterval = time.Microsecond + + frontend := httptest.NewServer(proxyHandler) + defer frontend.Close() + + req, _ := http.NewRequest("GET", frontend.URL, nil) + req.Close = true + + ctx, cancel := context.WithTimeout(req.Context(), 10*time.Second) + defer cancel() + req = req.WithContext(ctx) + + res, err := frontend.Client().Do(req) + if err != nil { + t.Fatalf("Get: %v", err) + } + defer res.Body.Close() + + if res.Header.Get("MyHeader") != expected { + t.Errorf("got header %q; expected %q", res.Header.Get("MyHeader"), expected) + } +} + func TestReverseProxyCancelation(t *testing.T) { const backendResponse = "I am the backend"