Log the request and response bodies for certain endpoints/handlers

[tomycastelli]

Hi! I am using Zerolog with the RequestLoggerWithConfig middleware, and I want to append to the same log the request and response bodies for certain handlers. I have tried using the provided BodyDump middleware but couldn't get it to append to the same log json produced by zerolog. Is there a way to do this?
This is the logging middleware:

        logger := logger.Get()
	e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
		LogURI:      true,
		LogStatus:   true,
		HandleError: true,
		LogValuesFunc: func(c echo.Context, v middleware.RequestLoggerValues) error {
			logger.Info().
				Str("id", c.Response().Header().Get(echo.HeaderXRequestID)).
				Str("URI", v.URI).
				Int("status", v.Status).
				Int64("latency", time.Since(v.StartTime).Milliseconds()).
				Str("ip", c.RealIP()).
				Msg("request")

			return nil
		},
	})

[harshagarwalnyu]

The issue is that RequestLoggerValues doesn't include the raw bodies by default. To log them with Zerolog in the same entry, you'll need to capture the bodies in a separate middleware and store them in the echo.Context so they're available to your LogValuesFunc later.

You have to be careful with the request body specifically: once it's read, it's exhausted, so you must "reset" it using io.NopCloser so your handlers can still access it.

Here is a clean way to set this up:

// 1. Middleware to capture bodies
e.Use(func(next echo.HandlerFunc) echo.HandlerFunc {
    return func(c echo.Context) error {
        if c.Request().Body != nil {
            reqBody, _ := io.ReadAll(c.Request().Body)
            c.Request().Body = io.NopCloser(bytes.NewBuffer(reqBody))
            c.Set("capturedReqBody", string(reqBody))
        }
        return next(c)
    }
})

// 2. Configure RequestLogger
e.Use(middleware.RequestLoggerWithConfig(middleware.RequestLoggerConfig{
    LogURI:    true,
    LogStatus: true,
    LogValuesFunc: func(c echo.Context, v middleware.RequestLoggerValues) error {
        reqBody, _ := c.Get("capturedReqBody").(string)
        
        logger.Info().
            Str("uri", v.URI).
            Int("status", v.Status).
            Str("body", reqBody).
            Msg("request")
        return nil
    },
}))

For response bodies, you would use a similar pattern but you'd need a custom wrapper for c.Response().Writer (like the one inside Echo's BodyDump middleware). Once you have that data in the context, your Zerolog output will stay structured and clean.