// userQuota is a handler that provides a rate limiter to the freegeoip API.
// It allows qmax requests per qintvl, in seconds.
//
// If redis is not available it responds with service unavailable.
func userQuota(rc *redis.Client, qmax int, qintvl int, f http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
var ip string
if idx := strings.LastIndex(r.RemoteAddr, ":"); idx != -1 {
ip = r.RemoteAddr[:idx]
} else {
ip = r.RemoteAddr
}
sreq, err := rc.Get(ip)
if err != nil {
serviceUnavailable(w, r, err.Error())
return
}
if len(sreq) == 0 {
err = rc.SetEx(ip, qintvl, "1")
if err != nil {
serviceUnavailable(w, r, err.Error())
return
}
f.ServeHTTP(w, r)
return
}
nreq, _ := strconv.Atoi(sreq)
if nreq >= qmax {
http.Error(w, "Quota exceeded", http.StatusForbidden)
return
}
_, err = rc.Incr(ip)
if err != nil {
context.Set(r, "log", err.Error())
}
f.ServeHTTP(w, r)
})
}
