Improve logging (#51)

* Improve logging

* fix test

dnsclient.go

@@ -2,7 +2,6 @@ package rdns
 
 import (
 	"crypto/tls"
-	"fmt"
 
 	"github.com/miekg/dns"
 	"github.com/sirupsen/logrus"
@@ -10,6 +9,7 @@ import (
 
 // DNSClient represents a simple DNS resolver for UDP or TCP.
 type DNSClient struct {
+	id       string
 	endpoint string
 	net      string
 	pipeline *Pipeline
@@ -19,12 +19,13 @@ var _ Resolver = &DNSClient{}
 
 // NewDNSClient returns a new instance of DNSClient which is a plain DNS resolver
 // that supports pipelining over a single connection.
-func NewDNSClient(endpoint, net string) *DNSClient {
+func NewDNSClient(id, endpoint, net string) *DNSClient {
 	client := &dns.Client{
 		Net:       net,
 		TLSConfig: &tls.Config{},
 	}
 	return &DNSClient{
+		id:       id,
 		net:      net,
 		endpoint: endpoint,
 		pipeline: NewPipeline(endpoint, client),
@@ -34,6 +35,7 @@ func NewDNSClient(endpoint, net string) *DNSClient {
 // Resolve a DNS query.
 func (d *DNSClient) Resolve(q *dns.Msg, ci ClientInfo) (*dns.Msg, error) {
 	Log.WithFields(logrus.Fields{
+		"id":       d.id,
 		"client":   ci.SourceIP,
 		"qname":    qName(q),
 		"resolver": d.endpoint,
@@ -46,5 +48,5 @@ func (d *DNSClient) Resolve(q *dns.Msg, ci ClientInfo) (*dns.Msg, error) {
 }
 
 func (d *DNSClient) String() string {
-	return fmt.Sprintf("DNS(%s)", d.endpoint)
+	return d.id
 }