# Revision history [back]

The old queue_size parameter not in the create_subscription method. Now it is integrated inside the rclcpp::Qos data structure as "depth" field.

There are a few built-in quality of services policies that you may want to use. These have some predefined values for its fields. For example, SensorDataQoS defines depth=10. Nonetheless, you could override this value using the Qos::keep_last(depth) method.

For example:

 rclcpp::SensorDataQoS qos;
qos.keep_last(*queueSize);
int queueSize = 10;
auto sub = node->create_subscription<MessageType>("topicName", qos, callbackfn);