/clock Topic Not Published and Unreal Engine 5.7 Build Fix

[shandilya1998]

Fixes: # 1. Build failure due to linking issues with libc++abi with Unreal Engine 5.7 clang toolchain
Fixes: # 2. Requests from Project AirSim C++ client not reaching sim server
Fixes: # 3. Timeout for failed requests not implemented on c++ client side causing further requests to be permanently blocked
Fixes: # 4. Timestamps from airsim not passed to published messages by the ROS2 client

About

1. Need to explicitly add -lc++abi in link options to ensure build compatibility with Unreal Engine 5.7's v26 clang toollchain
2. Uninitialised fis_canceled_ variable in class TAsyncResultProviderBase leads to garbage values in the variable which essentially cancels all incoming requests. /LoadScene coincidentlally works, however, none of the requests after scene is loaded work. Explicitly initialising fis_canceled_ fixes the issue. File changed is client/cpp/ProjectAirsimClientLib/src/AsyncResultInternal.h
3. Added request cancellation and timeout instructions to process failed requests to sim server in client/cpp/ProjectAirsimClientLib/src/Client.cpp
4. Overloaded MakeHeader and updated its usage in ros/projectairsim_ros2_cpp/src/projectairsim_ros2_cpp_node.cpp to ensure timestamps from unreal engine are published with ROS2 messages

How Has This Been Tested?

This was tested by setting up SITL with ardupilot and setting use_sim_time parameter for ardupilot to true. This forces ardupilot to use airsim timestamps. Previously it was observed that /clock topic has no published messages, which leads to a failed integration. However, after the fix the SITL setup works

Screenshots and videos (if appropriate):

ROS2 /clock topic echo output:

root@server1:/ws/sitl_ws/src/ue5/ProjectAirSim# ros2 topic echo /clock
A message was lost!!!
	total count change:1
	total count: 1---
clock:
  sec: 4514
  nanosec: 124000000
---
clock:
  sec: 4514
  nanosec: 124000000
---
clock:
  sec: 4514
  nanosec: 127000000
---
clock:
  sec: 4514
  nanosec: 130000000
---
clock:
  sec: 4514
  nanosec: 130000000
---
clock:
  sec: 4514
  nanosec: 133000000
---
clock:
  sec: 4514
  nanosec: 133000000
---
clock:
  sec: 4514
  nanosec: 136000000

This topic previously published nothing.

Refer to this link for a complete test with ArduPilot SITL. The video shows the published timestamps for IMU topics from Project AirSim ROS2 wrapper and ArduPilot SITL and the /clock topic published by Project AirSim ROS2 client.

[andrewjong]

FYI #177 also fixes this!

[LucasJSch]

Thank you for your contribution @shandilya1998! Nice work and observations 🦾

I'll answer by topic. Please update the code + description of this PR accordingly.

UE5.7 linking issue

I think the linking issues was solved as part of #162. Try rebasing your branch and let me know if you still see the issue.

C++ client requests not reaching sim server

Already solved before this PR, at least for the claimed fis_canceled_ cause. main branch already initializes fis_canceled_(false) in AsyncResultInternal.h.

Failed request timeout blocks later requests

I tested it locally, and this PR definitely solves the issue. Nice!

AirSim timestamps not passed to ROS2 messages

Also fixed by this PR, nice work!

[jonyMarino]

Thanks @shandilya1998, the sensor headers should retain the simulator's timestamp. If /clock isn't being published, that's the only solution. Additionally, we should implement a topic on the server to publish the clock instead of using the GetSimTime service.