feat: preventing process kill on port use
This commit is contained in:
Carlos Florêncio
@@ -243,9 +243,8 @@ func findFreePort() (int, error) {
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return port, nil
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}
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// ensurePortAvailable checks if the configured port is free. If not, it tries
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// to diagnose and clean up stale processes. If the port is still unavailable,
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// it falls back to an OS-assigned free port.
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// ensurePortAvailable checks if the configured port is free. If not, it
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// immediately falls back to an OS-assigned free port.
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func (l *Launcher) ensurePortAvailable() error {
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if err := checkPortAvailable(l.port); err == nil {
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return nil
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@@ -253,39 +252,14 @@ func (l *Launcher) ensurePortAvailable() error {
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originalPort := l.port
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// Port is in use — try to find and kill whatever is holding it
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l.logger.Warn("port in use, attempting to find and kill stale process",
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l.logger.Info("port already in use, selecting a free port",
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zap.Int("port", l.port))
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l.diagnosePID()
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if killed := l.tryKillPortHolder(); killed {
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// Wait briefly for the OS to release the port
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time.Sleep(500 * time.Millisecond)
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if err := checkPortAvailable(l.port); err == nil {
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l.logger.Info("port freed after killing stale process", zap.Int("port", l.port))
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return nil
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}
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}
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// Brief wait for TIME_WAIT to expire (up to 3s)
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l.logger.Warn("could not free port immediately, waiting for OS to release it",
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zap.Int("port", l.port))
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deadline := time.Now().Add(3 * time.Second)
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for time.Now().Before(deadline) {
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time.Sleep(500 * time.Millisecond)
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if err := checkPortAvailable(l.port); err == nil {
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l.logger.Info("port became available", zap.Int("port", l.port))
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return nil
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}
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}
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// Fall back to OS-assigned free port
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freePort, err := findFreePort()
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if err != nil {
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return fmt.Errorf("port %d is in use and failed to find alternative: %w", originalPort, err)
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}
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l.logger.Warn("configured port unavailable, using alternative",
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l.logger.Info("using alternative port",
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zap.Int("original_port", originalPort),
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zap.Int("new_port", freePort))
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l.port = freePort
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@@ -3,11 +3,6 @@
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package launcher
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import (
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"fmt"
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"net"
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"os"
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"os/exec"
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"strings"
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"syscall"
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"go.uber.org/zap"
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@@ -28,92 +23,3 @@ func (l *Launcher) gracefulStop(pid int) error {
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func (l *Launcher) forceKill(pid int) {
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_ = syscall.Kill(pid, syscall.SIGKILL)
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}
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// diagnosePID logs detailed info about what is holding the port (best-effort, non-fatal).
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func (l *Launcher) diagnosePID() {
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portStr := fmt.Sprintf(":%d", l.port)
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// Try lsof first
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if out, err := exec.Command("lsof", "-i", portStr, "-P", "-n").CombinedOutput(); err == nil {
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output := strings.TrimSpace(string(out))
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if output != "" {
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l.logger.Warn("lsof: process(es) holding port",
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zap.Int("port", l.port),
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zap.String("lsof_output", output))
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return
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}
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}
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// lsof found nothing — check netstat for TIME_WAIT / CLOSE_WAIT sockets
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if out, err := exec.Command("netstat", "-an").CombinedOutput(); err == nil {
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var matches []string
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search := fmt.Sprintf(".%d ", l.port) // macOS netstat uses dot separator
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search2 := fmt.Sprintf(":%d ", l.port) // Linux netstat uses colon
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for _, line := range strings.Split(string(out), "\n") {
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if strings.Contains(line, search) || strings.Contains(line, search2) {
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matches = append(matches, strings.TrimSpace(line))
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}
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}
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if len(matches) > 0 {
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l.logger.Warn("netstat: socket(s) on port (likely TIME_WAIT)",
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zap.Int("port", l.port),
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zap.String("netstat_output", strings.Join(matches, "\n")))
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return
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}
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}
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// Test IPv4 vs IPv6 separately to identify which is blocked
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v4Err := tryBind("tcp4", portStr)
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v6Err := tryBind("tcp6", portStr)
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l.logger.Warn("port in use but no process found — checking address families",
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zap.Int("port", l.port),
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zap.NamedError("ipv4_bind_err", v4Err),
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zap.NamedError("ipv6_bind_err", v6Err))
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}
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// tryBind attempts to bind to the given network/address and returns any error.
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func tryBind(network, addr string) error {
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ln, err := net.Listen(network, addr)
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if err != nil {
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return err
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}
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_ = ln.Close()
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return nil
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}
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// tryKillPortHolder tries to find and kill the process holding the port.
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// Returns true if it found and signaled a process.
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func (l *Launcher) tryKillPortHolder() bool {
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out, err := exec.Command("lsof", "-ti", fmt.Sprintf(":%d", l.port)).CombinedOutput()
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if err != nil || strings.TrimSpace(string(out)) == "" {
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return false
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}
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killed := false
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for _, line := range strings.Split(strings.TrimSpace(string(out)), "\n") {
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line = strings.TrimSpace(line)
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if line == "" {
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continue
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}
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pid := 0
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if _, err := fmt.Sscanf(line, "%d", &pid); err != nil || pid <= 0 {
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continue
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}
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if pid == os.Getpid() {
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continue
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}
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l.logger.Warn("killing stale process on port",
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zap.Int("port", l.port),
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zap.Int("pid", pid))
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if proc, err := os.FindProcess(pid); err == nil {
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if err := proc.Signal(syscall.SIGTERM); err != nil {
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l.logger.Debug("SIGTERM failed, trying SIGKILL",
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zap.Int("pid", pid),
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zap.Error(err))
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_ = proc.Kill()
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}
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killed = true
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}
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}
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return killed
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}
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@@ -3,10 +3,7 @@
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package launcher
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import (
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"fmt"
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"os"
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"os/exec"
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"strings"
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"go.uber.org/zap"
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)
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@@ -33,69 +30,3 @@ func (l *Launcher) forceKill(pid int) {
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_ = proc.Kill()
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}
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}
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// diagnosePID uses netstat to log what is holding the port (best-effort, non-fatal).
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func (l *Launcher) diagnosePID() {
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out, err := exec.Command("netstat", "-ano").CombinedOutput()
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if err != nil {
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l.logger.Debug("netstat failed", zap.Error(err))
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return
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}
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portStr := fmt.Sprintf(":%d ", l.port)
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var matches []string
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for _, line := range strings.Split(string(out), "\n") {
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if strings.Contains(line, portStr) {
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matches = append(matches, strings.TrimSpace(line))
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}
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}
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if len(matches) == 0 {
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l.logger.Warn("port in use but netstat found no process — likely TIME_WAIT or kernel hold",
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zap.Int("port", l.port))
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} else {
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l.logger.Warn("process(es) holding port",
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zap.Int("port", l.port),
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zap.String("netstat_output", strings.Join(matches, "\n")))
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}
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}
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// tryKillPortHolder tries to find and kill the process holding the port using netstat + taskkill.
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// Returns true if it found and signaled a process.
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func (l *Launcher) tryKillPortHolder() bool {
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out, err := exec.Command("netstat", "-ano").CombinedOutput()
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if err != nil {
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return false
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}
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portStr := fmt.Sprintf(":%d ", l.port)
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selfPid := os.Getpid()
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killed := false
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for _, line := range strings.Split(string(out), "\n") {
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if !strings.Contains(line, portStr) || !strings.Contains(line, "LISTENING") {
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continue
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}
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fields := strings.Fields(strings.TrimSpace(line))
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if len(fields) < 5 {
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continue
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}
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pid := 0
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if _, err := fmt.Sscanf(fields[len(fields)-1], "%d", &pid); err != nil || pid <= 0 {
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continue
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}
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if pid == selfPid {
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continue
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}
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l.logger.Warn("killing stale process on port",
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zap.Int("port", l.port),
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zap.Int("pid", pid))
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// taskkill /F /PID <pid>
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if killErr := exec.Command("taskkill", "/F", "/PID", fmt.Sprintf("%d", pid)).Run(); killErr != nil {
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l.logger.Debug("taskkill failed", zap.Int("pid", pid), zap.Error(killErr))
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} else {
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killed = true
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}
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}
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return killed
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}
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