Proxy

Proxy provides an HTTP/WebSocket reverse proxy middleware. It forwards a request to an upstream server using a configured load balancing technique.

In Echo v5.4.0 and v4.16.0, Proxy sets X-Forwarded-Proto from Context#Scheme() and removes X-Forwarded-Ssl, X-Forwarded-Protocol, and X-Url-Scheme before forwarding. Configure the scheme extractor for your trusted proxy chain. In v5, Proxy also sets X-Real-IP from Context#RealIP() rather than forwarding a client-supplied value. For a chain such as nginx → Echo Proxy → upstream, configure Echo#IPExtractor for the trusted incoming IP header as explained in IP Address.

All core middleware lives in the middleware package:

import "github.com/labstack/echo/v5/middleware"

Usage

url1, err := url.Parse("http://localhost:8081")
if err != nil {
  e.Logger.Error("failed to parse url", "error", err)
}
url2, err := url.Parse("http://localhost:8082")
if err != nil {
  e.Logger.Error("failed to parse url", "error", err)
}
e.Use(middleware.Proxy(middleware.NewRoundRobinBalancer([]*middleware.ProxyTarget{
  {
    URL: url1,
  },
  {
    URL: url2,
  },
})))

Custom configuration

e := echo.New()
e.Use(middleware.ProxyWithConfig(middleware.ProxyConfig{}))

Configuration

ProxyConfig · github.com/labstack/echo/v5@5196b9b

Fields from package source

Field	Type	Description	Source
Skipper	Skipper	Skipper defines a function to skip middleware.	L31
Balancer	ProxyBalancer	Balancer defines a load balancing technique. Required.	L35
RetryCount	int	RetryCount defines the number of times a failed proxied request should be retried using the next available ProxyTarget. Defaults to 0, meaning requests are never retried.	L39
RetryFilter	func(c *echo.Context, e error) bool	RetryFilter defines a function used to determine if a failed request to a ProxyTarget should be retried. The RetryFilter will only be called when the number of previous retries is less than RetryCount. If the function returns true, the request will be retried. The provided error indicates the reason for the request failure. When the ProxyTarget is unavailable, the error will be an instance of echo.HTTPError with a code of http.StatusBadGateway. In all other cases, the error will indicate an internal error in the Proxy middleware. When a RetryFilter is not specified, all requests that fail with http.StatusBadGateway will be retried. A custom RetryFilter can be provided to only retry specific requests. Note that RetryFilter is only called when the request to the target fails, or an internal error in the Proxy middleware has occurred. Successful requests that return a non-200 response code cannot be retried.	L53
ErrorHandler	func(c *echo.Context, err error) error	ErrorHandler defines a function which can be used to return custom errors from the Proxy middleware. ErrorHandler is only invoked when there has been either an internal error in the Proxy middleware or the ProxyTarget is unavailable. Due to the way requests are proxied, ErrorHandler is not invoked when a ProxyTarget returns a non-200 response. In these cases, the response is already written so errors cannot be modified. ErrorHandler is only invoked after all retry attempts have been exhausted.	L62
Rewrite	map[string]string	Rewrite defines URL path rewrite rules. The values captured in asterisk can be retrieved by index e.g. $1, $2 and so on. Examples: "/old": "/new", "/api/*": "/$1", "/js/*": "/public/javascripts/$1", "/users/*/orders/*": "/user/$1/order/$2",	L71
RegexRewrite	map[*regexp.Regexp]string	RegexRewrite defines rewrite rules using regexp.Rexexp with captures Every capture group in the values can be retrieved by index e.g. $1, $2 and so on. Example: "^/old/[0.9]+/": "/new", "^/api/.+?/(.*)": "/v2/$1",	L78
ContextKey	string	Context key to store selected ProxyTarget into context. Optional. Default value "target".	L82
Transport	http.RoundTripper	To customize the transport to remote. Examples: If custom TLS certificates are required.	L86
ModifyResponse	func(*http.Response) error	ModifyResponse defines function to modify response from ProxyTarget.	L89

Functions from package source

Type	Source
func Proxy(balancer ProxyBalancer) echo.MiddlewareFunc	L292
func ProxyWithConfig(config ProxyConfig) echo.MiddlewareFunc	L301

Default configuration

Name	Value
Skipper	DefaultSkipper
ContextKey	target

Regex-based rules

For advanced rewriting of proxy requests, rules may also be defined using regular expressions. Normal capture groups can be defined using () and referenced by index ($1, $2, …) in the rewritten path.

RegexRewrite and normal Rewrite rules can be combined.

e.Use(middleware.ProxyWithConfig(middleware.ProxyConfig{
  Balancer: rrb,
  Rewrite: map[string]string{
    "^/v1/*": "/v2/$1",
  },
  RegexRewrite: map[*regexp.Regexp]string{
    regexp.MustCompile("^/foo/([0-9].*)"):  "/num/$1",
    regexp.MustCompile("^/bar/(.+?)/(.*)"): "/baz/$2/$1",
  },
}))

See the reverse proxy cookbook for a complete example.