Method finalizeResponse

modules/caddyhttp/reverseproxy/reverseproxy.go:1210–1315

finalizeResponse prepares and copies the response.

(
	rw http.ResponseWriter,
	req *http.Request,
	res *http.Response,
	repl *caddy.Replacer,
	start time.Time,
	logger *zap.Logger,
)

// finalizeResponse prepares and copies the response.
func (h *Handler) finalizeResponse(
	rw http.ResponseWriter,
	req *http.Request,
	res *http.Response,
	repl *caddy.Replacer,
	start time.Time,
	logger *zap.Logger,
) error {
	// deal with 101 Switching Protocols responses: (WebSocket, h2c, etc)
	if res.StatusCode == http.StatusSwitchingProtocols {
		var wg sync.WaitGroup
		h.handleUpgradeResponse(logger, &wg, rw, req, res)
		wg.Wait()
		return nil
	}

	removeConnectionHeaders(res.Header)

	for _, h := range hopHeaders {
		res.Header.Del(h)
	}

	// delete our Server header and use Via instead (see #6275)
	rw.Header().Del("Server")
	var protoPrefix string
	if !strings.HasPrefix(strings.ToUpper(res.Proto), "HTTP/") {
		protoPrefix = res.Proto[:strings.Index(res.Proto, "/")+1]
	}
	rw.Header().Add("Via", fmt.Sprintf("%s%d.%d Caddy", protoPrefix, res.ProtoMajor, res.ProtoMinor))

	// apply any response header operations
	if h.Headers != nil && h.Headers.Response != nil {
		if h.Headers.Response.Require == nil ||
			h.Headers.Response.Require.Match(res.StatusCode, res.Header) {
			h.Headers.Response.ApplyTo(res.Header, repl)
		}
	}

	copyHeader(rw.Header(), res.Header)

	// The "Trailer" header isn't included in the Transport's response,
	// at least for *http.Transport. Build it up from Trailer.
	announcedTrailers := len(res.Trailer)
	if announcedTrailers > 0 {
		trailerKeys := make([]string, 0, len(res.Trailer))
		for k := range res.Trailer {
			trailerKeys = append(trailerKeys, k)
		}
		rw.Header().Add("Trailer", strings.Join(trailerKeys, ", "))
	}

	rw.WriteHeader(res.StatusCode)
	if h.VerboseLogs {
		logger.Debug("wrote header")
	}

	err := h.copyResponse(rw, res.Body, h.flushInterval(req, res), logger)
	errClose := res.Body.Close() // close now, instead of defer, to populate res.Trailer