Merge pull request moby#3745 from tonistiigi/github-etag-fix

http: ensure HEAD and GET requests have same headers

Author: AkihiroSuda

client/client_test.go

@@ -2189,6 +2189,13 @@ func testBuildHTTPSource(t *testing.T, sb integration.Sandbox) {
 	require.NoError(t, err)
 	require.Equal(t, []byte("content1"), dt)
 
+	allReqs := server.Stats("/foo").Requests
+	require.Equal(t, 2, len(allReqs))
+	require.Equal(t, http.MethodGet, allReqs[0].Method)
+	require.Equal(t, "gzip", allReqs[0].Header.Get("Accept-Encoding"))
+	require.Equal(t, http.MethodHead, allReqs[1].Method)
+	require.Equal(t, "gzip", allReqs[1].Header.Get("Accept-Encoding"))
+
 	// test extra options
 	st = llb.HTTP(server.URL+"/foo", llb.Filename("bar"), llb.Chmod(0741), llb.Chown(1000, 1000))
 

source/http/httpsource.go

@@ -178,6 +178,9 @@ func (hs *httpSourceHandler) CacheKey(ctx context.Context, g session.Group, inde
 	// manual ETag value comparison.
 	if len(m) > 0 {
 		req.Method = "HEAD"
+		// we need to add accept-encoding header manually because stdlib only adds it to GET requests
+		// some servers will return different etags if Accept-Encoding header is different
+		req.Header.Add("Accept-Encoding", "gzip")
 		resp, err := client.Do(req)
 		if err == nil {
 			if resp.StatusCode == http.StatusOK || resp.StatusCode == http.StatusNotModified {

util/testutil/httpserver/server.go

@@ -45,6 +45,7 @@ func (s *TestServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	s.stats[r.URL.Path].AllRequests++
+	s.stats[r.URL.Path].Requests = append(s.stats[r.URL.Path].Requests, newRequest(r))
 
 	if resp.LastModified != nil {
 		w.Header().Set("Last-Modified", resp.LastModified.Format(time.RFC850))
@@ -81,4 +82,21 @@ type Response struct {
 
 type Stat struct {
 	AllRequests, CachedRequests int
+	Requests                    []Request
+}
+
+type Request struct {
+	Method string
+	Header http.Header
+}
+
+func newRequest(r *http.Request) Request {
+	headers := http.Header{}
+	for k, v := range r.Header {
+		headers[k] = append([]string{}, v...)
+	}
+	return Request{
+		Method: r.Method,
+		Header: headers,
+	}
 }