internal/rproxy/request.go

@@ -384,8 +384,19 @@ func (rq *request) refuse(status int) {
 func (rq *request) finish(ctx context.Context) {
 	rq.stopTimers()
 
-	if rq.refused.Load() == 0 {
+	// After a cut-off answer, the reading of a body that has not arrived whole
-		rq.stopPassingOnBody()
+	// ends now. Go's server would otherwise keep the connection open while it
+	// reads the rest. A flush fails if the time to send the answer ran out, and
+	// every flush after a failed one fails too. ReverseProxy ignores the failure,
+	// but panics if it was still waiting for more of the app's answer; finish runs
+	// either way. Before a status, a flush would send a 200; after a 101,
+	// ReverseProxy has taken over the connection.
+	switch {
+	case rq.out.status != 0 && rq.out.status != http.StatusSwitchingProtocols &&
+		errors.Is(rq.rc.Flush(), os.ErrDeadlineExceeded):
+		rq.stopPassingOnBody(time.Now())
+	case rq.refused.Load() == 0:
+		rq.stopPassingOnBody(rq.requestDeadline())
 	}
 
 	requestEnd := rq.endRequest()
@@ -473,10 +484,10 @@ func (rq *request) stopReadingBody(deadline time.Time) {
 }
 
 // stopPassingOnBody ends the transport's reading of a visitor's body that has
-// not arrived whole, and lets Go's server read the rest until
+// not arrived whole, and lets Go's server read the rest until deadline. Go's
-// SWRP_MAX_REQUEST_TIME_MS runs out. Go's server reads it once the handler
+// server reads it once the handler returns, but with no deadline at all if
-// returns, but with no deadline at all if another read of it is still waiting.
+// another read of it is still waiting.
-func (rq *request) stopPassingOnBody() {
+func (rq *request) stopPassingOnBody(deadline time.Time) {
 	if rq.body == nil || rq.body.received.Load() {
 		return
 	}
@@ -489,7 +500,7 @@ func (rq *request) stopPassingOnBody() {
 	rq.body.stopped = true
 	rq.body.mu.Unlock()
 
-	rq.stopReadingBody(rq.requestDeadline())
+	rq.stopReadingBody(deadline)
 }
 
 // startRequestTimer starts SWRP_MAX_REQUEST_TIME_MS, which runs from the