package main import ( log "github.com/sirupsen/logrus" "math" "net" "net/http" "runtime" "strings" "sync" "time" ) var ( checkClient = &http.Client{ Timeout: 10 * time.Second, } ) type Server struct { Available bool Host string Path string Latitude float64 Longitude float64 } type ServerList []*Server func (s ServerList) checkLoop() { t := time.NewTicker(60 * time.Second) for { <-t.C s.Check() } } // Check will request the index from all servers // If a server does not respond in 10 seconds, it is considered offline. // This will wait until all checks are complete. func (s ServerList) Check() { var wg sync.WaitGroup for _, server := range s { wg.Add(1) go func(server *Server) { req, err := http.NewRequest(http.MethodGet, "https://"+server.Host+"/"+strings.TrimLeft(server.Path, "/"), nil) req.Header.Set("User-Agent", "ArmbianRouter/1.0 (Go "+runtime.Version()+")") if err != nil { // This should never happen. log.WithError(err).Warning("Invalid request! This should not happen, please check config.") wg.Done() return } res, err := checkClient.Do(req) if err != nil { if server.Available { log.WithField("server", server.Host).Info("Server went offline") server.Available = false } wg.Done() return } if (res.StatusCode == http.StatusOK || res.StatusCode == http.StatusMovedPermanently || res.StatusCode == http.StatusFound) && !server.Available { server.Available = true log.WithField("server", server.Host).Info("Server is online") } wg.Done() }(server) } wg.Wait() } // Closest will use GeoIP on the IP provided and find the closest server. // Return values are the closest server, the distance, and if an error occurred. func (s ServerList) Closest(ip net.IP) (*Server, float64, error) { var city City err := db.Lookup(ip, &city) if err != nil { return nil, -1, err } var closest *Server var closestDistance float64 = -1 for _, server := range s { if !server.Available { continue } distance := Distance(city.Location.Latitude, city.Location.Longitude, server.Latitude, server.Longitude) if closestDistance == -1 || distance < closestDistance { closestDistance = distance closest = server } } return closest, closestDistance, nil } // haversin(θ) function func hsin(theta float64) float64 { return math.Pow(math.Sin(theta/2), 2) } // Distance function returns the distance (in meters) between two points of // a given longitude and latitude relatively accurately (using a spherical // approximation of the Earth) through the Haversin Distance Formula for // great arc distance on a sphere with accuracy for small distances // // point coordinates are supplied in degrees and converted into rad. in the func // // distance returned is METERS!!!!!! // http://en.wikipedia.org/wiki/Haversine_formula func Distance(lat1, lon1, lat2, lon2 float64) float64 { // convert to radians // must cast radius as float to multiply later var la1, lo1, la2, lo2, r float64 la1 = lat1 * math.Pi / 180 lo1 = lon1 * math.Pi / 180 la2 = lat2 * math.Pi / 180 lo2 = lon2 * math.Pi / 180 r = 6378100 // Earth radius in METERS // calculate h := hsin(la2-la1) + math.Cos(la1)*math.Cos(la2)*hsin(lo2-lo1) return 2 * r * math.Asin(math.Sqrt(h)) }