net/http/httputil: flush ReverseProxy immediately if Content-Length is -1

Finish up a prior TODO by making ReverseProxy flush immediately
if Content-Length is -1, which is a case that can occur if for
example we have a streamed response, or chunked encoding, or when
the body's length wasn't known.

Fixes #41642

Change-Id: I30babaaf3e14837b99e3ecdc562a0a0e50c579bf
GitHub-Last-Rev: efc019a9fe361082d40bee77317018c3b80451a3
GitHub-Pull-Request: golang/go#41858
Reviewed-on: https://go-review.googlesource.com/c/go/+/260637
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>
Trust: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go
index 3f48fab544e912506e94f78b4eed8b23b5f31019..46e5f68a843732beb3e0d779463b46fe6cd0fa49 100644 (file)
--- a/src/net/http/httputil/reverseproxy.go
+++ b/src/net/http/httputil/reverseproxy.go
@@ -58,9 +58,9 @@ type ReverseProxy struct {
        // A negative value means to flush immediately
        // after each write to the client.
        // The FlushInterval is ignored when ReverseProxy
-       // recognizes a response as a streaming response;
-       // for such responses, writes are flushed to the client
-       // immediately.
+       // recognizes a response as a streaming response, or
+       // if its ContentLength is -1; for such responses, writes
+       // are flushed to the client immediately.
        FlushInterval time.Duration
 
        // ErrorLog specifies an optional logger for errors
@@ -325,7 +325,7 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 
        rw.WriteHeader(res.StatusCode)
 
-       err = p.copyResponse(rw, res.Body, p.flushInterval(req, res))
+       err = p.copyResponse(rw, res.Body, p.flushInterval(res))
        if err != nil {
                defer res.Body.Close()
                // Since we're streaming the response, if we run into an error all we can do
@@ -397,7 +397,7 @@ func removeConnectionHeaders(h http.Header) {
 
 // flushInterval returns the p.FlushInterval value, conditionally
 // overriding its value for a specific request/response.
-func (p *ReverseProxy) flushInterval(req *http.Request, res *http.Response) time.Duration {
+func (p *ReverseProxy) flushInterval(res *http.Response) time.Duration {
        resCT := res.Header.Get("Content-Type")
 
        // For Server-Sent Events responses, flush immediately.
@@ -406,7 +406,11 @@ func (p *ReverseProxy) flushInterval(req *http.Request, res *http.Response) time
                return -1 // negative means immediately
        }
 
-       // TODO: more specific cases? e.g. res.ContentLength == -1?
+       // We might have the case of streaming for which Content-Length might be unset.
+       if res.ContentLength == -1 {
+               return -1
+       }
+
        return p.FlushInterval
 }
 

diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go
index 764939fb0f0c26a6f2511e603d9cc9237808e4a4..ea786864d8ba221c7d9ce8573ce17489482dc1a3 100644 (file)
--- a/src/net/http/httputil/reverseproxy_test.go
+++ b/src/net/http/httputil/reverseproxy_test.go
@@ -1067,7 +1067,6 @@ func TestSelectFlushInterval(t *testing.T) {
        tests := []struct {
                name string
                p    *ReverseProxy
-               req  *http.Request
                res  *http.Response
                want time.Duration
        }{
@@ -1097,10 +1096,26 @@ func TestSelectFlushInterval(t *testing.T) {
                        p:    &ReverseProxy{FlushInterval: 0},
                        want: -1,
                },
+               {
+                       name: "Content-Length: -1, overrides non-zero",
+                       res: &http.Response{
+                               ContentLength: -1,
+                       },
+                       p:    &ReverseProxy{FlushInterval: 123},
+                       want: -1,
+               },
+               {
+                       name: "Content-Length: -1, overrides zero",
+                       res: &http.Response{
+                               ContentLength: -1,
+                       },
+                       p:    &ReverseProxy{FlushInterval: 0},
+                       want: -1,
+               },
        }
        for _, tt := range tests {
                t.Run(tt.name, func(t *testing.T) {
-                       got := tt.p.flushInterval(tt.req, tt.res)
+                       got := tt.p.flushInterval(tt.res)
                        if got != tt.want {
                                t.Errorf("flushLatency = %v; want %v", got, tt.want)
                        }