fixed findFreePort nil reference or conflict, made buildRoutes goroutine

src/go-proxy/utils.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+)
+
+type Utils struct {
+	PortsInUse map[int]bool
+	portsInUseMutex sync.Mutex
+}
+var utils = &Utils{
+	PortsInUse: make(map[int]bool),
+	portsInUseMutex: sync.Mutex{},
+}
+
+func (u *Utils) findFreePort(startingPort int) (int, error) {
+	for port := startingPort; port <= startingPort+100 && port <= 65535; port++ {
+		if u.PortsInUse[port] {
+			continue
+		}
+		addr := fmt.Sprintf(":%d", port)
+		l, err := net.Listen("tcp", addr)
+		if err == nil {
+			l.Close()
+			return port, nil
+		}
+	}
+	l, err := net.Listen("tcp", ":0")
+	if err == nil {
+		l.Close()
+		// NOTE: may not be after 20000
+		return l.Addr().(*net.TCPAddr).Port, nil
+	}
+	return -1, fmt.Errorf("unable to find free port: %v", err)
+}
+
+func (u *Utils) resetPortsInUse() {
+	u.portsInUseMutex.Lock()
+	defer u.portsInUseMutex.Unlock()
+	for port := range u.PortsInUse {
+		u.PortsInUse[port] = false
+	}
+}
+
+func (u* Utils) markPortInUse(port int) {
+	u.portsInUseMutex.Lock()
+	defer u.portsInUseMutex.Unlock()
+	u.PortsInUse[port] = true
+}
+
+func (*Utils) healthCheckHttp(targetUrl string) error {
+	// try HEAD first
+	// if HEAD is not allowed, try GET
+	resp, err := healthCheckHttpClient.Head(targetUrl)
+	if resp != nil {
+		defer resp.Body.Close()
+	}
+	if err != nil && resp != nil && resp.StatusCode == http.StatusMethodNotAllowed {
+		_, err = healthCheckHttpClient.Get(targetUrl)
+	}
+	if resp != nil {
+		defer resp.Body.Close()
+	}
+	return err
+}
+
+func (*Utils) healthCheckStream(scheme string, host string) error {
+	conn, err := net.DialTimeout(scheme, host, 5*time.Second)
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+	return nil
+}