We found that for some NetworkInterface objects, in this case on OsX, it was up, not a loopback, but still had a null MAC address (it was a tunnel). We suggest adding this extra if-statement around the return statement:

      if (!currentNic.isLoopback() && currentNic.isUp()) {
        byte[] macAddress = currentNic.getHardwareAddress();
        if (macAddress != null) {
          return Optional.of(macAddress);
        }
      }

Hello.

This is more like a question than an issue: Consider multiple independent services generating IDs on the same host/Mac address, how safe/unsafe is it to generate the node identifier for each service once at bootstrap with something like SecureRandom.nextLong?

Thanks a lot