'/clock' Topic cannot change each loop step time from simulation time

[fengzhongsu]

Bug report

Required Info:

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Steps to reproduce issue

In my node, i have publish topic '/clock' and set use_sim_time:=true. Although these settings change the results of this->now(), there is no implementation in which the frequency of program loops is independent of the simulation period.

Expected behavior

In ros1-Melodic, the same setting, will realize this result:

The first echo result is use_sim_time = false, and The second echo result is use_sim_time = true

Actual behavior

In ros2-foxy, humble also have these issue, like this:

when i set publish topic 'clock' and set use_sim_time:=true, the this->get_clock()->now() or this->now() can get the sim time, but the topic pub frequenct same not change by these settings.

[Barry-Xu-2018]

How do you create timer to publish messages ?
create_wall_timer or create_timer
Simulate time doesn't affect create_wall_timer.

[fengzhongsu]

您好，我已受到您的来信

[fengzhongsu]

How do you create timer to publish messages ? create_wall_timer or create_timer Simulate time doesn't affect create_wall_timer.

Hi, Barry. In simulation, i used rclcpp::Rate loop_rate(ctrl_freq); And In a
while(rclcpp::ok()) { rclcpp::spin_some(mynode); //my program loop_rate.sleep(); }

[Barry-Xu-2018]

Please note that rclcpp::Rate use RCL_SYSTEM_TIME in default. Do you change it ?

rclcpp/rclcpp/include/rclcpp/rate.hpp

Lines 133 to 146 in 348e22a

	class Rate : public RateBase
	{
	public:
	RCLCPP_SMART_PTR_DEFINITIONS(Rate)
	RCLCPP_PUBLIC
	explicit Rate(
	const double rate,
	Clock::SharedPtr clock = std::make_shared<Clock>(RCL_SYSTEM_TIME));
	RCLCPP_PUBLIC
	explicit Rate(
	const Duration & period,
	Clock::SharedPtr clock = std::make_shared<Clock>(RCL_SYSTEM_TIME));

[fengzhongsu]

Please note that rclcpp::Rate use RCL_SYSTEM_TIME in default. Do you change it ?

rclcpp/rclcpp/include/rclcpp/rate.hpp

Lines 133 to 146 in 348e22a

	class Rate : public RateBase
	{
	public:
	RCLCPP_SMART_PTR_DEFINITIONS(Rate)
	RCLCPP_PUBLIC
	explicit Rate(
	const double rate,
	Clock::SharedPtr clock = std::make_shared<Clock>(RCL_SYSTEM_TIME));
	RCLCPP_PUBLIC
	explicit Rate(
	const Duration & period,
	Clock::SharedPtr clock = std::make_shared<Clock>(RCL_SYSTEM_TIME));

I have been set use_sim_time=true
https://design.ros2.org/articles/clock_and_time.html

[fujitatomoya]

I have been set use_sim_time=true
https://design.ros2.org/articles/clock_and_time.html

use_sim_time is set on the node, but Rate object. with your example, as @Barry-Xu-2018 mentions, Rate is instantiated with system time as default, not simulation time. I think you need to set RCL_SYSTEM_TIME for Rate, the it can get the time from simulation clock.

this->get_clock()->now() or this->now() can get the sim time,

assuming that this is the Node. because the use_sim_time is set to true, clock belongs to node is now set to simulation clock. so that it can get simulation clock.

[Barry-Xu-2018]

As fujitatomoya said，you should modify code on creating Rate.

rclcpp::Rate loop_rate(ctrl_freq, std::make_shared(RCL_ROS_TIME));

[fengzhongsu]

As fujitatomoya said，you should modify code on creating Rate.

rclcpp::Rate loop_rate(ctrl_freq, std::make_shared(RCL_ROS_TIME));
I have tried add this code. But have some error in IDE, my ros2 version is foxy
error: no matching function for call to ‘make_shared(rcl_clock_type_t)’
268 | rclcpp::Rate loop_rate(ctrl_freq, std::make_shared(RCL_ROS_TIME));

[fujitatomoya]

I have tried add this code. But have some error in IDE, my ros2 version is foxy

Foxy is already E.O.L, can you use humble or later instead?

[Barry-Xu-2018]

For Foxy, you should create a Clock with RCL_ROS_TIME

rclcpp/rclcpp/include/rclcpp/clock.hpp

Lines 53 to 66 in b0c25d5

	class Clock
	{
	public:
	RCLCPP_SMART_PTR_DEFINITIONS(Clock)
	/// Default c'tor
	/**
	* Initializes the clock instance with the given clock_type.
	*
	* \param clock_type type of the clock.
	* \throws anything rclcpp::exceptions::throw_from_rcl_error can throw.
	*/
	RCLCPP_PUBLIC
	explicit Clock(rcl_clock_type_t clock_type = RCL_SYSTEM_TIME);

Create a new "Rate" like with above Clock.

rclcpp/rclcpp/include/rclcpp/rate.hpp

Line 115 in b0c25d5

using Rate = GenericRate<std::chrono::system_clock>;

BTW, foxy is EOL.
So it's best to upgrade to the Humble or Iron version.