Add checking if port reqired to start server is free

cmd/agent/run.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"net"
 	"net/http"
 	"os"
 	"os/signal"
@@ -270,6 +271,7 @@ func watchExitErrors(ctx context.Context, log *logrus.Entry, exitCh chan error,
 func runPProf(cfg config.Config, log *logrus.Entry, exitCh chan error) (closeFunc func()) {
 	log.Infof("starting pprof server on port: %d", cfg.PprofPort)
 	addr := portToServerAddr(cfg.PprofPort)
+	checkPort(addr, "pprof", log)
 	pprofSrv := &http.Server{Addr: addr, Handler: http.DefaultServeMux}
 	closeFn := func() {
 		log.Infof("closing pprof server")
@@ -297,8 +299,9 @@ func runHealthzEndpoints(cfg config.Config, log *logrus.Entry, checks map[string
 	allChecks := lo.Assign(map[string]healthz.Checker{
 		"server": healthz.Ping,
 	}, checks)
-
-	healthzSrv := &http.Server{Addr: portToServerAddr(cfg.HealthzPort), Handler: &healthz.Handler{Checks: allChecks}}
+	addr := portToServerAddr(cfg.HealthzPort)
+	checkPort(addr, "healthz", log)
+	healthzSrv := &http.Server{Addr: addr, Handler: &healthz.Handler{Checks: allChecks}}
 	closeFunc := func() {
 		log.Infof("closing healthz server")
 		if err := healthzSrv.Close(); err != nil {
@@ -320,6 +323,16 @@ func runHealthzEndpoints(cfg config.Config, log *logrus.Entry, checks map[string
 	return closeFunc
 }
 
+func checkPort(address string, serverName string, log *logrus.Entry) {
+	listener, err := net.Listen("tcp", address)
+	if err != nil {
+		log.Errorf("port required to start %s server is not free, address: %s, error: %v", serverName, address, err)
+		return
+	}
+	defer listener.Close() // Close the listener
+	log.Infof("port required to start %s server is free, address: %s", serverName, address)
+}
+
 func portToServerAddr(port int) string {
 	return fmt.Sprintf(":%d", port)
 }