Avoid port conflict in address manager.

integration/addr/manager.go

@@ -1,12 +1,44 @@
 package addr
 
 import (
+	"fmt"
 	"net"
+	"sync"
+	"time"
 )
 
-// Suggest suggests a address a process can listen on. It returns
-// a tuple consisting of a free port and the hostname resolved to its IP.
-func Suggest() (port int, resolvedHost string, err error) {
+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+	// remove outdated port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() (port int, resolvedHost string, err error) {
 	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
 	if err != nil {
 		return
@@ -22,3 +54,21 @@ func Suggest() (port int, resolvedHost string, err error) {
 	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() (port int, resolvedHost string, err error) {
+	for i := 0; i < portConflictRetry; i++ {
+		port, resolvedHost, err = suggest()
+		if err != nil {
+			return
+		}
+		if cache.add(port) {
+			return
+		}
+	}
+	err = fmt.Errorf("no free ports found after %d retries", portConflictRetry)
+	return
+}