recreate the control socket after a crash; fixes bblfsh#286

Signed-off-by: Denys Smirnov <[email protected]>

cmd/bblfshd/main.go

@@ -197,9 +197,37 @@ func listenUser(d *daemon.Daemon) {
 	}
 }
 
+func unwrap(err error) error {
+	switch err := err.(type) {
+	case *net.OpError:
+		return unwrap(err.Err)
+	case *os.SyscallError:
+		return unwrap(err.Err)
+	}
+	return err
+}
+
+func isErrno(err error, eno syscall.Errno) bool {
+	if e, _ := unwrap(err).(syscall.Errno); e == eno {
+		return true
+	}
+	return false
+}
+
+func isAddrInUse(err error) bool {
+	return isErrno(err, syscall.EADDRINUSE)
+}
+
 func listenControl(d *daemon.Daemon) {
 	var err error
 	ctlListener, err = net.Listen(*ctl.network, *ctl.address)
+	if isAddrInUse(err) && *ctl.network == "unix" {
+		// bblfshd may have crashed and left the socket file
+		// remove it and try again
+		logrus.Warningf("control socket %s (%s) already exists, but is not active; re-creating", *ctl.address, *ctl.network)
+		_ = os.Remove(*ctl.address)
+		ctlListener, err = net.Listen(*ctl.network, *ctl.address)
+	}
 	if err != nil {
 		logrus.Fatalf("error creating control listener: %s", err)
 	}