1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
|
package dnscache
// Package dnscache caches DNS lookups
import (
"net"
"sync"
"time"
)
type Resolver struct {
lock sync.RWMutex
cache map[string][]net.IP
}
func New(refreshRate time.Duration) *Resolver {
resolver := &Resolver {
cache: make(map[string][]net.IP, 64),
}
if refreshRate > 0 {
go resolver.autoRefresh(refreshRate)
}
return resolver
}
func (r *Resolver) Fetch(address string) ([]net.IP, error) {
r.lock.RLock()
ips, exists := r.cache[address]
r.lock.RUnlock()
if exists { return ips, nil }
return r.Lookup(address)
}
func (r *Resolver) FetchOne(address string) (net.IP, error) {
ips, err := r.Fetch(address)
if err != nil || len(ips) == 0 { return nil, err}
return ips[0], nil
}
func (r *Resolver) FetchOneString(address string) (string, error) {
ip, err := r.FetchOne(address)
if err != nil || ip == nil { return "", err }
return ip.String(), nil
}
func (r *Resolver) Refresh() {
i := 0
r.lock.RLock()
addresses := make([]string, len(r.cache))
for key, _ := range r.cache {
addresses[i] = key
i++
}
r.lock.RUnlock()
for _, address := range addresses {
r.Lookup(address)
time.Sleep(time.Second * 2)
}
}
func (r *Resolver) Lookup(address string) ([]net.IP, error) {
ips, err := net.LookupIP(address)
if err != nil { return nil, err }
r.lock.Lock()
r.cache[address] = ips
r.lock.Unlock()
return ips, nil
}
func (r *Resolver) autoRefresh(rate time.Duration) {
for {
time.Sleep(rate)
r.Refresh()
}
}
|
