How do you manage dependencies and versions for ROS nodes and services?

1 Why dependencies and versions matter

Nodes and services depend on various packages, libraries, and frameworks to perform their functions. For example, a node that controls a robot arm might depend on a package that provides kinematics and motion planning algorithms, or a service that performs image recognition might depend on a library that implements neural networks. These dependencies have their own versions, which might change over time due to updates, bug fixes, or new features. If you do not manage your dependencies and versions properly, you might end up with incompatible or outdated nodes and services, which can cause failures, crashes, or unexpected behaviors.

2 How to specify dependencies and versions

One of the first steps to manage your dependencies and versions is to specify them clearly and explicitly in your project files. ROS provides a standard way to do this using the package.xml and CMakeLists.txt files. The package.xml file contains the metadata of your package, such as its name, description, license, and dependencies. The CMakeLists.txt file contains the instructions to build your package, such as the source files, libraries, executables, and tests. In both files, you can use tags and variables to indicate the dependencies and versions of your nodes and services. For example, you can use the <depend> tag in the package.xml file to list the packages that your package depends on, and the find_package() function in the CMakeLists.txt file to find and link the libraries that your package requires.

3 How to install dependencies and versions

Once you have specified your dependencies and versions, you need to install them on your system or environment. ROS provides several tools and methods to help you do this. One of the most common and convenient ways is to use the rosdep tool, which can automatically install the dependencies of your package from the official ROS repositories or other sources. You can run rosdep with the command rosdep install --from-paths <path-to-your-package> --ignore-src, which will scan your package.xml file and install the missing dependencies. Another way is to use the catkin tool, which can build your package and its dependencies from source. You can run catkin with the command catkin_make, which will create a build directory and a devel directory in your workspace, where you can find the compiled binaries and libraries of your package and its dependencies.

4 How to manage versions and updates

Even after you have installed your dependencies and versions, you might need to update them from time to time to get the latest features, bug fixes, or security patches. ROS provides several tools and methods to help you do this. One of the most common and convenient ways is to use the apt tool, which can update your packages from the official ROS repositories or other sources. You can run apt with the command sudo apt update && sudo apt upgrade, which will check for new versions of your packages and install them. Another way is to use the wstool tool, which can update your packages from source. You can run wstool with the command wstool update, which will pull the latest changes from the remote repositories of your packages.

5 How to test dependencies and versions

Before you deploy your nodes and services, you should test them to make sure they work as expected with your dependencies and versions. ROS provides several tools and methods to help you do this. One of the most common and convenient ways is to use the roslaunch tool, which can launch multiple nodes and services with a single command. You can run roslaunch with the command roslaunch <package-name> <launch-file-name>, which will start the nodes and services defined in the launch file. You can also use the rostest tool, which can run unit tests and integration tests for your nodes and services. You can run rostest with the command rostest <package-name> <test-file-name>, which will execute the tests defined in the test file.

6 How to document dependencies and versions

Finally, you should document your dependencies and versions to make your nodes and services easier to understand, reuse, and maintain. ROS provides several tools and methods to help you do this. One of the most common and convenient ways is to use the rosdoc_lite tool, which can generate documentation for your package from the package.xml and CMakeLists.txt files, as well as from the comments in your source code. You can run rosdoc_lite with the command rosdoc_lite <path-to-your-package>, which will create a doc directory in your package, where you can find the HTML files of your documentation. You can also use the roswiki tool, which can upload your documentation to the official ROS wiki, where you can share it with other developers and users.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?