fixup! agent/http: refactor proxy for simpler error handling

Use send time instead of channel.

pkg/agent/protocol/http/proxy.go

@@ -99,17 +99,18 @@ func (h *httpHandler) isExcluded(r *http.Request) bool {
 }
 
 // proxy proxies a request to the upstream URL.
-// Request is performed immediately, but response won't be copied to the client until wait has been consumed.
-func (h *httpHandler) proxy(rw http.ResponseWriter, req *http.Request, wait <-chan time.Time) {
+// Request is performed immediately, but response won't be sent until sendAt.
+func (h *httpHandler) proxy(rw http.ResponseWriter, req *http.Request, delay time.Duration) {
+	timer := time.After(delay)
+
 	upstreamReq := req.Clone(context.Background())
 	upstreamReq.Host = h.upstreamURL.Host
 	upstreamReq.URL.Host = h.upstreamURL.Host
 	upstreamReq.URL.Scheme = h.upstreamURL.Scheme
 	upstreamReq.RequestURI = "" // It is an error to set this field in an HTTP client request.
 
 	response, err := h.client.Do(req)
-	<-wait
-
+	<-timer
 	if err != nil {
 		rw.WriteHeader(http.StatusBadGateway)
 		_, _ = fmt.Fprint(rw, err)
@@ -136,9 +137,9 @@ func (h *httpHandler) proxy(rw http.ResponseWriter, req *http.Request, wait <-ch
 	_, _ = io.Copy(rw, response.Body)
 }
 
-// fault consumes wait and then writes to rw the configured error code and body.
-func (h *httpHandler) fault(rw http.ResponseWriter, wait <-chan time.Time) {
-	<-wait
+// fault sleeps until sendAt and then writes the configured error downstream.
+func (h *httpHandler) fault(rw http.ResponseWriter, delay time.Duration) {
+	time.Sleep(delay)
 
 	rw.WriteHeader(int(h.disruption.ErrorCode))
 	_, _ = rw.Write([]byte(h.disruption.ErrorBody))
@@ -147,7 +148,7 @@ func (h *httpHandler) fault(rw http.ResponseWriter, wait <-chan time.Time) {
 func (h *httpHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 	if h.isExcluded(req) {
 		//nolint:contextcheck // Unclear which context the linter requires us to propagate here.
-		h.proxy(rw, req, time.After(0))
+		h.proxy(rw, req, 0)
 		return
 	}
 
@@ -157,15 +158,13 @@ func (h *httpHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		delay += time.Duration(variation - 2*rand.Int63n(variation))
 	}
 
-	responseTimer := time.After(delay)
-
 	if h.disruption.ErrorRate > 0 && rand.Float32() <= h.disruption.ErrorRate {
-		h.fault(rw, responseTimer)
+		h.fault(rw, delay)
 		return
 	}
 
 	//nolint:contextcheck // Unclear which context the linter requires us to propagate here.
-	h.proxy(rw, req, responseTimer)
+	h.proxy(rw, req, delay)
 }
 
 // Start starts the execution of the proxy