/
manager.go
77 lines (70 loc) · 1.54 KB
/
manager.go
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package addr
import (
"fmt"
"net"
"sync"
"time"
)
const (
portReserveTime = 1 * time.Minute
portConflictRetry = 100
)
type portCache struct {
lock sync.Mutex
ports map[int]time.Time
}
func (c *portCache) add(port int) bool {
c.lock.Lock()
defer c.lock.Unlock()
// remove outdated port
for p, t := range c.ports {
if time.Since(t) > portReserveTime {
delete(c.ports, p)
}
}
// try allocating new port
if _, ok := c.ports[port]; ok {
return false
}
c.ports[port] = time.Now()
return true
}
var cache = &portCache{
ports: make(map[int]time.Time),
}
func suggest(listenHost string) (port int, resolvedHost string, err error) {
if listenHost == "" {
listenHost = "localhost"
}
addr, err := net.ResolveTCPAddr("tcp", net.JoinHostPort(listenHost, "0"))
if err != nil {
return
}
l, err := net.ListenTCP("tcp", addr)
if err != nil {
return
}
port = l.Addr().(*net.TCPAddr).Port
defer func() {
err = l.Close()
}()
resolvedHost = addr.IP.String()
return
}
// Suggest suggests an address a process can listen on. It returns
// a tuple consisting of a free port and the hostname resolved to its IP.
// It makes sure that new port allocated does not conflict with old ports
// allocated within 1 minute.
func Suggest(listenHost string) (port int, resolvedHost string, err error) {
for i := 0; i < portConflictRetry; i++ {
port, resolvedHost, err = suggest(listenHost)
if err != nil {
return
}
if cache.add(port) {
return
}
}
err = fmt.Errorf("no free ports found after %d retries", portConflictRetry)
return
}