Proxy

Proxy fornece um middleware de reverse proxy HTTP/WebSocket. Ele encaminha um request para um servidor upstream usando uma técnica de load balancing configurada.

Todo o middleware principal fica no pacote middleware:

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

Uso

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,
  },
})))

Configuração customizada

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

Configuração

type ProxyConfig struct {
  // Skipper defines a function to skip middleware.
  Skipper Skipper

  // Balancer defines a load balancing technique.
  // Required.
  Balancer ProxyBalancer

  // 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.
  RetryCount int

  // 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.
  RetryFilter func(c *echo.Context, e error) bool

  // 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.
  ErrorHandler func(c *echo.Context, err error) error

  // 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",
  Rewrite map[string]string

  // RegexRewrite defines rewrite rules using regexp.Regexp 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",
  RegexRewrite map[*regexp.Regexp]string

  // Context key to store selected ProxyTarget into context.
  // Optional. Default value "target".
  ContextKey string

  // To customize the transport to remote.
  // Examples: If custom TLS certificates are required.
  Transport http.RoundTripper

  // ModifyResponse defines function to modify response from ProxyTarget.
  ModifyResponse func(*http.Response) error
}

Configuração padrão

Nome	Valor
Skipper	DefaultSkipper
ContextKey	target

Regras baseadas em regex

Para reescrita avançada de requests de proxy, as regras também podem ser definidas usando expressões regulares. Grupos de captura normais podem ser definidos com () e referenciados por índice ($1, $2, …) no caminho reescrito.

Regras RegexRewrite e Rewrite normais podem ser combinadas.

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",
  },
}))

Veja a receita de reverse proxy para um exemplo completo.