Method ToMiddleware

middleware/proxy.go:306–413

ToMiddleware converts ProxyConfig to middleware or returns an error for invalid configuration

()

// ToMiddleware converts ProxyConfig to middleware or returns an error for invalid configuration
func (config ProxyConfig) ToMiddleware() (echo.MiddlewareFunc, error) {
	if config.Skipper == nil {
		config.Skipper = DefaultProxyConfig.Skipper
	}
	if config.ContextKey == "" {
		config.ContextKey = DefaultProxyConfig.ContextKey
	}
	if config.Balancer == nil {
		return nil, errors.New("echo proxy middleware requires balancer")
	}
	if config.RetryFilter == nil {
		config.RetryFilter = func(c *echo.Context, e error) bool {
			if httpErr, ok := e.(*echo.HTTPError); ok {
				return httpErr.Code == http.StatusBadGateway
			}
			return false
		}
	}
	if config.ErrorHandler == nil {
		config.ErrorHandler = func(c *echo.Context, err error) error {
			return err
		}
	}

	if config.Rewrite != nil {
		if config.RegexRewrite == nil {
			config.RegexRewrite = make(map[*regexp.Regexp]string)
		}
		maps.Copy(config.RegexRewrite, rewriteRulesRegex(config.Rewrite))
	}

	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c *echo.Context) (err error) {
			if config.Skipper(c) {
				return next(c)
			}

			req := c.Request()
			res := c.Response()
			if err := rewriteURL(config.RegexRewrite, req); err != nil {
				return config.ErrorHandler(c, err)
			}

			// Fix header
			// Basically it's not good practice to unconditionally pass incoming x-real-ip header to upstream.
			// However, for backward compatibility, legacy behavior is preserved unless you configure Echo#IPExtractor.
			if req.Header.Get(echo.HeaderXRealIP) == "" || c.Echo().IPExtractor != nil {
				req.Header.Set(echo.HeaderXRealIP, c.RealIP())
			}
			if req.Header.Get(echo.HeaderXForwardedProto) == "" {
				req.Header.Set(echo.HeaderXForwardedProto, c.Scheme())
			}
			if c.IsWebSocket() { // For HTTP, this is set by Go HTTP reverse proxy.
				// Append, not set, to preserve the incoming chain from upstream proxies.
				prior := req.Header[echo.HeaderXForwardedFor]
				if len(prior) > 0 {
					req.Header.Set(echo.HeaderXForwardedFor, strings.Join(prior, ", ")+", "+c.RealIP())
				} else {