Welcome to the documentation for realtime_tools
Contains a set of tools that can be used from a hard realtime thread, without breaking the realtime behavior.
For more information of the ros2_control framework see control.ros.org.
RealtimePublisher
The realtime_tools::RealtimePublisher allows users that write C++ ros2_controllers to publish messages on a ROS topic from a hard realtime loop. The normal ROS publisher is not realtime safe, and should not be used from within the update loop of a realtime controller. The realtime publisher is a wrapper around the ROS publisher; the wrapper creates an extra non-realtime thread that publishes messages on a ROS topic. The example below shows a typical usage of the realtime publisher in the on_configure() (non-realtime method) and update() (realtime method) methods of a realtime controller:
#include <realtime_tools/realtime_publisher.hpp>
class MyController : public controller_interface::ControllerInterface
{
...
private:
std::unique_ptr<realtime_tools::RealtimePublisher<my_msgs::msg::MyMsg>> state_publisher_;
std::shared_ptr<rclcpp::Publisher<my_msgs::msg::MyMsg>> s_publisher_;
my_msgs::msg::MyMsg some_msg_;
}
controller_interface::CallbackReturn MyController::on_configure(
const rclcpp_lifecycle::State & /*previous_state*/)
{
...
s_publisher_ = get_node()->create_publisher<my_msgs::msg::MyMsg>(
"~/status", rclcpp::SystemDefaultsQoS());
state_publisher_ =
std::make_unique<realtime_tools::RealtimePublisher<my_msgs::msg::MyMsg>>(s_publisher_);
some_msg_.header.frame_id = params_.frame_id;
...
}
controller_interface::return_type MyController::update(
const rclcpp::Time & /*time*/, const rclcpp::Duration & /*period*/)
{
...
// Publish controller state
some_msg_.header.stamp = get_node()->now();
// Fill in the rest of the message
....
state_publisher_->try_publish(some_msg_);
}