func dnsMetricsHandler(next dns.Handler) dns.HandlerFunc {
return func(w dns.ResponseWriter, req *dns.Msg) {
var (
prot = "unknown"
qtype = "unknown"
rcode = "unknown"
buffer = &cachingWriter{ResponseWriter: w}
start = time.Now()
)
if _, ok := w.RemoteAddr().(*net.UDPAddr); ok {
prot = "udp"
} else if _, ok := w.RemoteAddr().(*net.TCPAddr); ok {
prot = "tcp"
}
if len(req.Question) == 1 {
qtype = dns.TypeToString[req.Question[0].Qtype]
}
next.ServeDNS(buffer, req)
if buffer.last != nil {
rcode = dns.RcodeToString[buffer.last.Rcode]
}
duration := float64(time.Since(start)) / float64(time.Second)
dnsDurations.WithLabelValues(prot, qtype, rcode).Observe(duration)
}
}
func dnsLoggingHandler(logger *log.Logger, next dns.Handler) dns.HandlerFunc {
return func(w dns.ResponseWriter, r *dns.Msg) {
next.ServeDNS(&loggingWriter{
ResponseWriter: w,
logger: logger,
start: time.Now(),
}, r)
}
}
// TODO(alx): Settle on naming for handlers acting as middleware.
func protocolHandler(maxAnswers int, next dns.Handler) dns.Handler {
return dns.HandlerFunc(func(w dns.ResponseWriter, r *dns.Msg) {
next.ServeDNS(&truncatingWriter{w, maxAnswers}, r)
})
}