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Design the ROS2 implementation for Clock class #575

Merged
merged 7 commits into from
Nov 26, 2022
Merged

Design the ROS2 implementation for Clock class #575

merged 7 commits into from
Nov 26, 2022

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GiulioRomualdi
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@GiulioRomualdi GiulioRomualdi commented Nov 18, 2022 •
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This PR develops the ROS2 implementation for the Clock class in the system component. This PR uses plain CMake instead of ament_cmake (provided by ROS2). The required ROS version is humble.

The clock can be used as follows:

  1. In c++
#include <BipedalLocomotion/System/RosClock.h>
#include <BipedalLocomotion/System/Clock.h>

#include <chrono>
#include <memory>

using namespace std::chrono_literals;

int main(int argc, char *argv[])
{
    BipedalLocomotion::System::ClockBuilder::setFactory(std::make_shared<BipedalLocomotion::System::RosClockFactory>(argc, argv));

    BipedalLocomotion::clock().sleepFor(2000ms);

    return 0;
}
  1. In python
import bipedal_locomotion_framework as blf
import sys
import datetime

# Call this function to set the ros clock
blf.system.ClockBuilder.set_factory(blf.system.RosClockFactory(args=sys.argv))

start = blf.clock().now()
blf.clock().sleep_for(datetime.timedelta(seconds=7))

@GiulioRomualdi GiulioRomualdi self-assigned this Nov 18, 2022
@traversaro
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@GiulioRomualdi GiulioRomualdi requested a review from traversaro

I am supposed to wait for it being not Draft.

@GiulioRomualdi
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Actually yes, there is a problem related to

m_clock.sleep_for(...)

function.
There seems that the context is not valid.
Looking online there seems that I should call rclcpp::init() before calling the clock functions, however this method should be called only once for each ROS node. So a possibility is to check if this has been already called by someone else and if not call it

@GiulioRomualdi GiulioRomualdi force-pushed the clock/ros2 branch 2 times, most recently from 7c5dd45 to 01dd947 Compare November 22, 2022 16:27
@GiulioRomualdi GiulioRomualdi marked this pull request as ready for review November 22, 2022 16:27
@GiulioRomualdi
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The PR is ready

S-Dafarra
S-Dafarra reviewed Nov 22, 2022
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src/System/RosImplementation/src/RosClock.cpp Outdated

void RosClock::yield()
{
std::this_thread::yield();
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Does it make sense to mix ROS2 and std calls? Is it better to simply do anything?

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You're right. Removed

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Not a big problem, but it could make sense to have std::this_thread::yield() in this context. In the end, sleep/sleepUntil are functions that in the end are waiting on some kind of OS synchronization primitive (mutex/condition variables), so it could make sense that you want to yield even if you are waiting on those. Anyhow, I do not think it is a big problem.

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I just thought that the effect could have not been very predictable given the sleep implementation of ROS2, but maybe I am being paranoid.

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In ros we should use the command spin so in theory yield is not needed. Shall we add a debug print that remember the user that this implementation of yield does nothing?

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Shall we add a debug print that remember the user that this implementation of yield does nothing?

I would avoid the print, as it would make writing generic code quite difficult (you would need to not call yield if you use the ROS2 clock). I would say let's merge it empty (safest choice), and then let's see if problems emerge.

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Ok merged thank you all as usual ❤️

@traversaro
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@GiulioRomualdi GiulioRomualdi requested a review from traversaro

I am supposed to wait for it being not Draft.

Sorry, that was originally meant to be a question, I put a . just for a typo.

@GiulioRomualdi GiulioRomualdi mentioned this pull request Nov 24, 2022
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@GiulioRomualdi GiulioRomualdi merged commit 2a66363 into master Nov 26, 2022
@GiulioRomualdi GiulioRomualdi deleted the clock/ros2 branch November 26, 2022 13:58
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@S-Dafarra S-Dafarra S-Dafarra left review comments

@traversaro traversaro traversaro approved these changes

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