Write headers manually for streaming response writers before calling Flush()

Signed-off-by: Christopher Petito <47751006+krissetto@users.noreply.github.com>

api/server/httputils/write_log_stream.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"net/http"
 	"net/url"
 	"sort"
 
@@ -17,9 +18,14 @@ import (
 // WriteLogStream writes an encoded byte stream of log messages from the
 // messages channel, multiplexing them with a stdcopy.Writer if mux is true
 func WriteLogStream(_ context.Context, w io.Writer, msgs <-chan *backend.LogMessage, config *container.LogsOptions, mux bool) {
+	// Used before the Flush(), so we don't set the header twice because of the otel wrapper
+	// see here: https://github.com/moby/moby/issues/47448
+	if rw, ok := w.(http.ResponseWriter); ok {
+		rw.WriteHeader(http.StatusOK)
+	}
+
 	wf := ioutils.NewWriteFlusher(w)
 	defer wf.Close()
-
 	wf.Flush()
 
 	outStream := io.Writer(wf)

daemon/stats.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"net/http"
 	"runtime"
 	"time"
 
@@ -46,6 +47,12 @@ func (daemon *Daemon) ContainerStats(ctx context.Context, prefixOrName string, c
 
 	outStream := config.OutStream
 	if config.Stream {
+		// Used before the Flush(), so we don't set the header twice because of the otel wrapper
+		// see here: https://github.com/moby/moby/issues/47448
+		if rw, ok := outStream.(http.ResponseWriter); ok {
+			rw.WriteHeader(http.StatusOK)
+		}
+
 		wf := ioutils.NewWriteFlusher(outStream)
 		defer wf.Close()
 		wf.Flush()