final ClientInvocationServiceImpl invocationService =getClientInvocationService(context);
if (key == null) {
future = invocationService.invokeOnRandomTarget(request, handler);
} else {
future = invocationService.invokeOnKeyOwner(request, key, handler);
}
String registrationId = context.getSerializationService().toObject(future.get());
invocationService.registerListener(registrationId, request.getCallId());
return registrationId;
} catch (Exception e) {