log.go

package middleware

import (
	"net"
	"net/http"
	"time"

	"goa.design/goa/middleware"
)

// Log returns a middleware that logs incoming HTTP requests and outgoing
// responses. The middleware uses the request ID set by the RequestID middleware
// or creates a short unique request ID if missing for each incoming request and
// logs it with the request and corresponding response details.
//
// The middleware logs the incoming requests HTTP method and path as well as the
// originator of the request. The originator is computed by looking at the
// X-Forwarded-For HTTP header or - absent of that - the originating IP. The
// middleware also logs the response HTTP status code, body length (in bytes) and
// timing information.
func Log(l middleware.Logger) func(h http.Handler) http.Handler {
	return func(h http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			reqID := r.Context().Value(middleware.RequestIDKey)
			if reqID == nil {
				reqID = shortID()
			}
			started := time.Now()

			l.Log("id", reqID,
				"req", r.Method+" "+r.URL.String(),
				"from", from(r))

			rw := CaptureResponse(w)
			h.ServeHTTP(rw, r)

			l.Log("id", reqID,
				"status", rw.StatusCode,
				"bytes", rw.ContentLength,
				"time", time.Since(started).String())
		})
	}
}

// from makes a best effort to compute the request client IP.
func from(req *http.Request) string {
	if f := req.Header.Get("X-Forwarded-For"); f != "" {
		return f
	}
	f := req.RemoteAddr
	ip, _, err := net.SplitHostPort(f)
	if err != nil {
		return f
	}
	return ip
}