2.1.4. ROS 2 System Handle¶
The ROS 2 System Handle can be used for two main purposes:
Connection between a ROS 2 application and an application running over a different middleware implementation. This is the classic use-case for Integration Service.
Connecting two ROS 2 applications running under different Domain IDs.
The only dependency of this System Handle is to have a ROS 2 installation (Foxy or superior) in your system.
Regarding the ROS 2 System Handle, there are several specific parameters which can be configured for the ROS 2 middleware. All of these parameters are optional, and are suboptions of the main five sections:
systems: The system
ros2. In addition to the
types-fromfields, the ROS 2 System Handle accepts the following specific configuration fields:
systems: ros2: type: ros2 namespace: "/" node_name: "my_ros2_node" domain: 4
namespace: The namespace of the ROS 2 node created by the ROS 2 System Handle.
node_name: The ROS 2 System Handle node name.
domain: Provides with an easy way to change the Domain ID of the ROS 2 entities created by the ROS 2 System Handle.
There are several examples that you can find in this documentation in which the ROS 2 System Handle is employed in the communication process. Some of them are presented here:
220.127.116.11. Compilation flags¶
Besides the Global compilation flags available for the whole Integration Service product suite, there are some specific flags which apply only to the ROS 2 System Handle; they are listed below:
BUILD_ROS2_TESTS: Allows to specifically compile the ROS 2 System Handle unitary and integration tests. It is useful to avoid compiling each System Handle’section test suite present in the
colconworkspace, which is what would happen if using the
BUILD_TESTSflag, with the objective of minimizing building time. To use it, after making sure that the ROS 2 System Handle is present in your
colconworkspace, execute the following command:
~/is_ws$ colcon build --cmake-args -DBUILD_ROS2_TESTS=ON
IS_ROS2_DISTRO: This flag is intended to select the ROS 2 distro that should be used to compile the ROS 2 System Handle. If not set, the version will be retrieved from the last ROS distro sourced in the compilation environment; this means that if the last ROS environment sourced corresponds to ROS 1, the compilation process will stop and warn the user about it.
MIX_ROS_PACKAGES: It accepts as an argument a list of ROS packages, such as
nav_msgs… for which the required transformation library to convert the specific ROS 2 type definitions into xTypes, and the other way around, will be built. This list is shared with the ROS 1 System Handle, meaning that the ROS packages specified in the MIX_ROS_PACKAGES variable will also be built for ROS 1 if the corresponding System Handle is present within the Integration Service workspace. To avoid possible errors, if a certain package is only present in ROS 2, the MIX_ROS2_PACKAGES flag must be used instead.
These transformation libraries are also known within the Integration Service context as
Middleware Interface Extensionor
By default, only the
std_msgs_mixlibrary is compiled, unless the
BUILD_ROS2_TESTSis used, case in which some additional ROS 2 packages
mixfiles required for testing will be built.
If the user wants to compile some additional packages to use them with Integration Service, the following command must be launched to compile it, adding as much packages to the list as desired:
~/is_ws$ colcon build --cmake-args -DMIX_ROS_PACKAGES="std_msgs geometry_msgs sensor_msgs nav_msgs"
MIX_ROS2_PACKAGES: It is used just as the MIX_ROS_PACKAGES flag, but will only affect ROS 2; this means that the mix generation engine will not search within the ROS 1 packages, allowing to compile specific ROS 2 packages independently.
For example, if a user wants to compile a certain package dummy_msgs independently from ROS 2, but compiling std_msgs and geometry_msgs for both the ROS 1 and ROS 2 System Handles, the following command should be executed:
~/is_ws$ colcon build --cmake-args -DMIX_ROS_PACKAGES="std_msgs geometry_msgs" -DMIX_ROS2_PACKAGES="dummy_msgs"