Request Logger

El middleware RequestLogger registra información sobre cada request HTTP. Te permite personalizar por completo qué se registra y cómo, por lo que encaja bien con bibliotecas de terceros de logging estructurado.

Los valores que el logger puede extraer se controlan con los campos booleanos y slices de RequestLoggerConfig. Habilita un campo (por ejemplo LogStatus: true) para que su valor se rellene en RequestLoggerValues, que se pasa a tu LogValuesFunc.

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

  // BeforeNextFunc is called before the next middleware or handler in the chain.
  BeforeNextFunc func(c *echo.Context)

  // LogValuesFunc is called with the values extracted by the logger from the
  // request/response.
  // Mandatory.
  LogValuesFunc func(c *echo.Context, v RequestLoggerValues) error

  // HandleError instructs the logger to call the global error handler when the next
  // middleware/handler returns an error. A side effect is that the response is then
  // committed and sent, so middlewares up the chain can no longer change the status
  // code or body.
  HandleError bool

  // LogLatency records the duration of the rest of the handler chain (the next(c) call).
  LogLatency bool
  // LogProtocol extracts the request protocol (for example HTTP/1.1 or HTTP/2).
  LogProtocol bool
  // LogRemoteIP extracts the request remote IP. See echo.Context.RealIP() for details.
  LogRemoteIP bool
  // LogHost extracts the request host value (for example example.com).
  LogHost bool
  // LogMethod extracts the request method (for example GET).
  LogMethod bool
  // LogURI extracts the request URI (for example /list?lang=en&page=1).
  LogURI bool
  // LogURIPath extracts the request URI path part (for example /list).
  LogURIPath bool
  // LogRoutePath extracts the route path the request matched (for example /user/:id).
  LogRoutePath bool
  // LogRequestID extracts the request ID from the X-Request-ID request header, or the
  // response if the request did not have a value.
  LogRequestID bool
  // LogReferer extracts the request referer value.
  LogReferer bool
  // LogUserAgent extracts the request user agent value.
  LogUserAgent bool
  // LogStatus extracts the response status code. If the chain returns an echo.HTTPError,
  // the status code is taken from it.
  LogStatus bool
  // LogError extracts the error returned from the handler chain.
  LogError bool
  // LogContentLength extracts the Content-Length header value. Note: this can differ
  // from the actual request body size as it may be spoofed.
  LogContentLength bool
  // LogResponseSize extracts the response content length. Note: when used with Gzip
  // middleware this value may not always be correct.
  LogResponseSize bool
  // LogHeaders extracts the given list of request headers. A slice of values is logged
  // per header since a request can contain more than one. Names are canonicalized with
  // http.CanonicalHeaderKey (for example "accept-encoding" becomes "Accept-Encoding").
  LogHeaders []string
  // LogQueryParams extracts the given list of query parameters from the request URI. A
  // slice of values is logged per name since a request can repeat a parameter.
  LogQueryParams []string
  // LogFormValues extracts the given list of form values from the request body and URI.
  // A slice of values is logged per name since a request can repeat a value.
  LogFormValues []string
}

Ejemplos

fmt.Printf

skipper := func(c *echo.Context) bool {
  // Skip the health check endpoint.
  return c.Request().URL.Path == "/health"
}
e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
  LogStatus: true,
  LogURI:    true,
  Skipper:   skipper,
  BeforeNextFunc: func(c *echo.Context) {
    c.Set("customValueFromContext", 42)
  },
  LogValuesFunc: func(c *echo.Context, v middleware.RequestLoggerValues) error {
    value, _ := c.Get("customValueFromContext").(int)
    fmt.Printf("REQUEST: uri: %v, status: %v, custom-value: %v\n", v.URI, v.Status, value)
    return nil
  },
}))

Salida de ejemplo:

REQUEST: uri: /hello, status: 200, custom-value: 42

slog (log/slog)

logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
  LogStatus:   true,
  LogURI:      true,
  LogError:    true,
  HandleError: true, // forwards the error to the global error handler so it can pick the status code
  LogValuesFunc: func(c *echo.Context, v middleware.RequestLoggerValues) error {
    if v.Error == nil {
      logger.LogAttrs(context.Background(), slog.LevelInfo, "REQUEST",
        slog.String("uri", v.URI),
        slog.Int("status", v.Status),
      )
    } else {
      logger.LogAttrs(context.Background(), slog.LevelError, "REQUEST_ERROR",
        slog.String("uri", v.URI),
        slog.Int("status", v.Status),
        slog.String("err", v.Error.Error()),
      )
    }
    return nil
  },
}))

Salida de ejemplo:

{"time":"2024-12-30T20:55:46.2399999+08:00","level":"INFO","msg":"REQUEST","uri":"/hello","status":200}

Zerolog (rs/zerolog)

logger := zerolog.New(os.Stdout)
e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
  LogURI:    true,
  LogStatus: true,
  LogValuesFunc: func(c *echo.Context, v middleware.RequestLoggerValues) error {
    logger.Info().
      Str("URI", v.URI).
      Int("status", v.Status).
      Msg("request")
    return nil
  },
}))

Salida de ejemplo:

{"level":"info","URI":"/hello","status":200,"message":"request"}

Zap (uber-go/zap)

logger, _ := zap.NewProduction()
e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
  LogURI:    true,
  LogStatus: true,
  LogValuesFunc: func(c *echo.Context, v middleware.RequestLoggerValues) error {
    logger.Info("request",
      zap.String("URI", v.URI),
      zap.Int("status", v.Status),
    )
    return nil
  },
}))

Salida de ejemplo:

{"level":"info","ts":1735564026.3197417,"caller":"cmd/main.go:20","msg":"request","URI":"/hello","status":200}

Logrus (sirupsen/logrus)

log := logrus.New()
e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
  LogURI:    true,
  LogStatus: true,
  LogValuesFunc: func(c *echo.Context, values middleware.RequestLoggerValues) error {
    log.WithFields(logrus.Fields{
      "URI":    values.URI,
      "status": values.Status,
    }).Info("request")
    return nil
  },
}))

Salida de ejemplo:

time="2024-12-30T21:08:49+08:00" level=info msg=request URI=/hello status=200

Solución de problemas

panic: missing LogValuesFunc callback function for request logger middleware

Este panic ocurre cuando el callback obligatorio LogValuesFunc se deja sin configurar. Define una función que coincida con la firma de LogValuesFunc y asígnala en la configuración:

func logValues(c *echo.Context, v middleware.RequestLoggerValues) error {
  fmt.Printf("Request Method: %s, URI: %s\n", v.Method, v.URI)
  return nil
}

e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
  LogValuesFunc: logValues,
}))

Los parámetros en los logs están vacíos

Si valores como v.URI y v.Status están vacíos dentro de LogValuesFunc, comprueba que los flags de extracción correspondientes (LogStatus, LogURI, etc.) estén establecidos en true en la configuración. Cada valor solo se rellena cuando su flag está habilitado.