CARLA ue5-dev: how to change ROS_DOMAIN_ID

[ali-0-1]

Platform: Ubuntu 22.04 - ue5-dev branch built from source

Ros Humble already installed.

ROS_DOMAIN_ID is hard coded and by default set to 0.

All publisher and subscribers in ros2 folder (LibCarla/source/carla/ros2/) which have

factory->create_participant(0, pqos)

needs to be modified.

First we need to define a config file like this in ros2 folder

LibCarla/source/carla/ros2/ROS2Config.h

  #pragma once
  
  #include <cstdint>
  
  namespace carla {
  namespace ros2 {
  
  uint32_t GetDomainId();
  
  } // namespace ros2
  } // namespace carla

---

Declare it in ROS2.cpp
/LibCarla/source/carla/ros2/ROS2.cpp
In ros2 {...}

  namespace carla {
  namespace ros2 {

  //Add this
    uint32_t GetDomainId()
  {
      const char *env = std::getenv("ROS_DOMAIN_ID");
      if (!env)
          return 0;
      return static_cast<uint32_t>(std::atoi(env));
  }

  // static fields
  std::shared_ptr<ROS2> ROS2::_instance;

---

Then modify all the code containing create_participant(0, pqos) by adding #include "carla/ros2/ROS2Config.h"

We can find all files that has create_participant(0, pqos), with this command running from CARLA root:

:~/CarlaUE5$ grep -R "create_participant(0" -n LibCarla/source/carla/ros2

Note that some files have it defined in multiple places, change all places.

---

Example of implementation:

LibCarla/source/carla/ros2/publishers/BasicPublisher.cpp

  #include "BasicPublisher.h"
  
  #include <string>
  
  #include "carla/ros2/ROS2Config.h" //this is our config file
  
  #include "carla/ros2/types/String.h"
  #include "carla/ros2/types/StringPubSubTypes.h"
  #include "carla/ros2/listeners/CarlaListener.h"
  
  #include <fastdds/dds/domain/DomainParticipant.hpp>
  #include <fastdds/dds/publisher/Publisher.hpp>
  #include <fastdds/dds/topic/Topic.hpp>
  #include <fastdds/dds/publisher/DataWriter.hpp>
  #include <fastdds/dds/topic/TypeSupport.hpp>
  
  #include <fastdds/dds/domain/qos/DomainParticipantQos.hpp>
  #include <fastdds/dds/domain/DomainParticipantFactory.hpp>
  #include <fastdds/dds/publisher/qos/PublisherQos.hpp>
  #include <fastdds/dds/topic/qos/TopicQos.hpp>
  
  #include <fastrtps/attributes/ParticipantAttributes.h>
  #include <fastrtps/qos/QosPolicies.h>
  #include <fastdds/dds/publisher/qos/DataWriterQos.hpp>
  #include <fastdds/dds/publisher/DataWriterListener.hpp>
  
  
  namespace carla {
  namespace ros2 {
    namespace efd = eprosima::fastdds::dds;
    using erc = eprosima::fastrtps::types::ReturnCode_t;
  
    struct BasicPublisherImpl {
      efd::DomainParticipant* _participant { nullptr };
      efd::Publisher* _publisher { nullptr };
      efd::Topic* _topic { nullptr };
      efd::DataWriter* _datawriter { nullptr };
      efd::TypeSupport _type { new std_msgs::msg::StringPubSubType() };
      CarlaListener _listener {};
      std_msgs::msg::String _message {};
    };
  
    bool BasicPublisher::Init() {
      if (_impl->_type == nullptr) {
          std::cerr << "Invalid TypeSupport" << std::endl;
          return false;
      }
      efd::DomainParticipantQos pqos = efd::PARTICIPANT_QOS_DEFAULT;
      pqos.name(_name);
      auto factory = efd::DomainParticipantFactory::get_instance();

      // here it is hard coded to zero
      // _impl->_participant = factory->create_participant(0, pqos);
      
     // now can get it from defined domain id
      auto domain = GetDomainId();
      _impl->_participant = factory->create_participant(domain, pqos);


      if (_impl->_participant == nullptr) {
          std::cerr << "Failed to create DomainParticipant" << std::endl;
          return false;
      }
      _impl->_type.register_type(_impl->_participant);
  
      efd::PublisherQos pubqos = efd::PUBLISHER_QOS_DEFAULT;
      _impl->_publisher = _impl->_participant->create_publisher(pubqos, nullptr);
      if (_impl->_publisher == nullptr) {
        std::cerr << "Failed to create Publisher" << std::endl;
        return false;
      }
  
      efd::TopicQos tqos = efd::TOPIC_QOS_DEFAULT;
      const std::string topic_name { "rt/basic_publisher_example" };
      _impl->_topic = _impl->_participant->create_topic(topic_name, _impl->_type->getName(), tqos);
      if (_impl->_topic == nullptr) {
          std::cerr << "Failed to create Topic" << std::endl;
          return false;
      }
  
      efd::DataWriterQos wqos = efd::DATAWRITER_QOS_DEFAULT;
      efd::DataWriterListener* listener = (efd::DataWriterListener*)_impl->_listener._impl.get();
      _impl->_datawriter = _impl->_publisher->create_datawriter(_impl->_topic, wqos, listener);
      if (_impl->_datawriter == nullptr) {
          std::cerr << "Failed to create DataWriter" << std::endl;
          return false;
      }
      _frame_id = _name;
      return true;
    }
    +++ other existing code +++

---

Another example:
LibCarla/source/carla/ros2/subscribers/CarlaEgoVehicleControlSubscriber.cpp:

  #include "carla/ros2/ROS2Config.h"
  
  bool CarlaEgoVehicleControlSubscriber::Init() {
      if (_impl->_type == nullptr) {
          std::cerr << "Invalid TypeSupport" << std::endl;
          return false;
      }
  
      efd::DomainParticipantQos pqos = efd::PARTICIPANT_QOS_DEFAULT;
      pqos.name(_name);
      auto factory = efd::DomainParticipantFactory::get_instance();


      // here it is hard coded
      // _impl->_participant = factory->create_participant(0, pqos);

      // now can get it from defined domain id
      auto domain = GetDomainId();         
      _impl->_participant = factory->create_participant(domain, pqos);

      if (_impl->_participant == nullptr) {
          std::cerr << "Failed to create DomainParticipant" << std::endl;
          return false;
      }

---

After modifying the all files run below command to build

      cmake --build Build --target launch

NOTE: By default it is still 0, we just need to assign domain id before launching the CARLA and use the same domain id in all terminals to isolate our topics in that domain...

Example usage:
from CARLA root :~/CarlaUE5$

  export ROS_DOMAIN_ID=33
  
  cmake --build Build --target launch-only

Run the level and in another clean terminal:

  export ROS_DOMAIN_ID=33      
  source /opt/ros/humble/setup.bash 
  ros2 topic list

we will get:
/clock
/parameter_events
/rosout

/clock is coming from CARLA 💯
Remember in all terminal dealing with ros, needs to be exported with same domain id, it can be added to ./bashrc to make the terminal having it by start up, if it is constant all the time as well.

[ali-0-1]

---------------------------------------------------

SAME FOR UPDATED SOURCE CODE

---------------------------------------------------

Carla Unreal ue5-dev

Engine version: 5.5.4

Ubuntu 24.04

This time we have Jazzy Jalisco

Define the same config file header

LibCarla/source/carla/ros2/ROS2Config.h

  #pragma once
  
  #include <cstdint>
  
  namespace carla {
  namespace ros2 {
  
  uint32_t GetDomainId();
  
  } // namespace ros2
  } // namespace carla

Define the config file cpp separately not in ROS2.cpp

LibCarla/source/carla/ros2/ROS2Config.cpp

#include "carla/ros2/ROS2Config.h"  
#include <cstdlib>  

namespace carla {
namespace ros2 {

uint32_t GetDomainId()
{
    const char *env = std::getenv("ROS_DOMAIN_ID");  
    if (!env)
        return 0;

    return static_cast<uint32_t>(std::atoi(env));
}  
} // namespace ros2
} // namespace carla

---

Modify hard coded files

---

In this version we have only 3 files to modify:

LibCarla/source/carla/ros2/publishers/PublisherImpl.h

modify as below

// add header
#include "carla/ros2/ROS2Config.h"

// turn this to comment or remove
// _participant = factory->create_participant(0, pqos);
auto domain = GetDomainId();
_participant = factory->create_participant(domain, pqos);

---

LibCarla/source/carla/ros2/subscribers/SubscriberImpl.h

modify as below

// add header
#include "carla/ros2/ROS2Config.h"

// turn this to comment or remove
// _participant = factory->create_participant(0, pqos);
auto domain = GetDomainId();
_participant = factory->create_participant(domain, pqos);

---

LibCarla/source/carla/ros2/subscribers/BasicSubscriber.cpp

modify as below

// add header
#include "carla/ros2/ROS2Config.h"

// turn this to comment or remove
// _impl->_participant = factory->create_participant(0, pqos);
auto domain = GetDomainId();
_impl->_participant = factory->create_participant(domain, pqos);

---

Modify CMAKE LIST

---

We also need to modify CmakeLists to add the config file into compiler path

Ros2Native/LibCarlaRos2Native/CMakeLists.txt

just after the

file (
  GLOB
  LIBCARLA_ROS2_SOURCES
  ${LIBCARLA_SOURCE_PATH}/carla/ros2/publishers/*.cpp
  ${LIBCARLA_SOURCE_PATH}/carla/ros2/subscribers/*.cpp
  ${LIBCARLA_SOURCE_PATH}/carla/ros2/listeners/*.cpp
  ${LIBCARLA_SOURCE_PATH}/carla/ros2/types/*.cpp
)

add this:

list (
  APPEND
  LIBCARLA_ROS2_SOURCES
  ${LIBCARLA_SOURCE_PATH}/carla/ros2/ROS2Config.cpp
)

---

After modifying the all files run below command to build

  cmake --build Build --target launch

NOTE: By default it is still 0, we just need to assign domain id before launching the CARLA and use the same domain id in all terminals to isolate our topics in that domain...

Example usage:
from CARLA root :~/CarlaUE5$

export ROS_DOMAIN_ID=33

cmake --build Build --target launch-only

Run the level and in another clean terminal:

export ROS_DOMAIN_ID=33      
source /opt/ros/jazzy/setup.bash 
ros2 topic list

we will get:
/clock is from Carla
/parameter_events
/rosout

---

---

In case your Carla Build fails, do below if necessary:

The below is not related to domain id setup but for some reason experienced this after some settings, may be after installing the Jazzy, Unreal compiler and Ubuntu compiler mismatched

cmake --build Build

command started to fail. It started to throw this carla_studio_example_tool error:

[0/2] Re-checking globbed directories... 
[3/15] Linking CXX executable Examples/QtClient/carla_studio_example_tool 
FAILED: Examples/QtClient/carla_studio_example_tool

It has been resolved by modifying Toolchain.cmake

CMake/Toolchain.cmake

replace this:

add_link_options (-stdlib=libc++ -L${UE_LIBS} )

with:

add_link_options (
    -stdlib=libc++
    -L${UE_LIBS}
    -L/lib/x86_64-linux-gnu
    -L/usr/lib/x86_64-linux-gnu
    -Wl,-rpath-link,/lib/x86_64-linux-gnu
    -Wl,-rpath-link,/usr/lib/x86_64-linux-gnu
)