リクエストロガー

RequestLogger ミドルウェアは各 HTTP リクエストの情報をログに記録します。何をどのように記録するかを完全にカスタマイズできるため、サードパーティの（構造化ログ）ライブラリとの利用に適しています。

logger が抽出できる値は、RequestLoggerConfig の bool フィールドと slice フィールドで制御されます。フィールドを有効化する（例：LogStatus: true）と、その値が LogValuesFunc に渡される RequestLoggerValues に設定されます。

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
}

例

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
  },
}))

出力例：

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
  },
}))

出力例：

{"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
  },
}))

出力例：

{"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
  },
}))

出力例：

{"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
  },
}))

出力例：

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

トラブルシューティング

panic: missing LogValuesFunc callback function for request logger middleware

この panic は、必須の LogValuesFunc callback が未設定のときに発生します。 LogValuesFunc シグネチャに一致する関数を定義し、設定に割り当ててください。

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,
}))

ログ内のパラメーターが空

LogValuesFunc 内で v.URI や v.Status などが空の場合、対応する抽出フラグ（LogStatus、LogURI など）が設定で true になっているか確認してください。各値は、そのフラグが有効な場合にのみ設定されます。