Add documentation for Gazebo vendor packages (#443)

Signed-off-by: Addisu Z. Taddese <[email protected]>
Co-authored-by: Alejandro Hernández Cordero <[email protected]>

index.yaml

@@ -23,6 +23,11 @@ pages:
     title: ROS/Gazebo Installation
     file: ros_installation.md
     description: Our development plans.
+    children:
+      - name: ros2_gz_vendor_pkgs
+        title: ROS 2 Gazebo Vendor Packages
+        file: ros2_gz_vendor_pkgs.md
+        description: Using ROS 2 Gazebo Vendor packages
   - name: migrating_gazebo_classic_ros2_packages
     title: Migration from ROS 2 Gazebo Classic
     file: migrating_gazebo_classic_ros2_packages.md

ros2_gz_vendor_pkgs.md

@@ -0,0 +1,177 @@
+# ROS 2 Gazebo Vendor Packages
+
+ROS 2 versions prior to Jazzy used Gazebo packages that were available in
+upstream Ubuntu. However, due to the package
+[update policy of Ubuntu](https://wiki.ubuntu.com/StableReleaseUpdates), the
+Gazebo packages on upstream Ubuntu did not receive any updates. Thus, upstream
+Ubuntu almost always had older versions of Gazebo than what was available from
+the Gazebo package repository ([packages.osrfoundation.org](packages.osrfoundation.org)). To overcome this,
+more up-to-date Gazebo packages were copied to the ROS bootstrap repository
+([repos.ros.org](repos.ros.org)) which were then copied to the main ROS package repository
+([packages.ros.org](packages.ros.org)). However, the process was error prone and keeping package
+versions in sync between the Gazebo and ROS package repositories was difficult
+since this was a manual process.
+
+As of ROS 2 Jazzy, Gazebo is available from the ROS package repository via
+vendor packages. A ROS vendor package is a ROS package that provides software
+that ROS needs on platforms where it might not be available, or where a
+different version than what is available is required [^1].
+
+The Gazebo vendor packages provide all of the Gazebo libraries to a given ROS
+release. The packages are built in the ROS buildfarm and as part of their build
+process, fetch the sources of the underlying Gazebo library and build it. In
+addition, the vendor packages provide CMake shims that make it possible to use
+CMake targets without version numbers.
+
+Each release of ROS 2 is paired with a specific release of Gazebo. For ROS 2
+Jazzy, the vendor packages contain Gazebo libraries from the Harmonic release.
+For ROS 2 K-turtle (next release), the vendor packages will contain Gazebo
+Ionic. This default pairing is found in the
+[ROS installation instructions](https://gazebosim.org/docs/harmonic/ros_installation)
+
+The following is a table of all vendor packages and the underlying Gazebo
+library they vendor:
+
+| Vendor Package                                                                   | Gazebo Library                                              |
+| -------------------------------------------------------------------------------- | ----------------------------------------------------------- |
+| [gz_cmake_vendor](https://github.com/gazebo-release/gz_cmake_vendor)             | [gz-cmake](https://github.com/gazebosim/gz-cmake)           |
+| [gz_common_vendor](https://github.com/gazebo-release/gz_common_vendor)           | [gz-common](https://github.com/gazebosim/gz-common)         |
+| [gz_fuel_tools_vendor](https://github.com/gazebo-release/gz_fuel_tools_vendor)   | [gz-fuel-tools](https://github.com/gazebosim/gz-fuel-tools) |
+| [gz_gui_vendor](https://github.com/gazebo-release/gz_gui_vendor)                 | [gz-gui](https://github.com/gazebosim/gz-gui)               |
+| [gz_launch_vendor](https://github.com/gazebo-release/gz_launch_vendor.git)       | [gz-launch](https://github.com/gazebosim/gz-launch)         |
+| [gz_math_vendor](https://github.com/gazebo-release/gz_math_vendor.git)           | [gz-math](https://github.com/gazebosim/gz-math)             |
+| [gz_msgs_vendor](https://github.com/gazebo-release/gz_msgs_vendor.git)           | [gz-msgs](https://github.com/gazebosim/gz-msgs)             |
+| [gz_physics_vendor](https://github.com/gazebo-release/gz_physics_vendor.git)     | [gz-physics](https://github.com/gazebosim/gz-physics)       |
+| [gz_plugin_vendor](https://github.com/gazebo-release/gz_plugin_vendor.git)       | [gz-plugin](https://github.com/gazebosim/gz-plugin)         |
+| [gz_rendering_vendor](https://github.com/gazebo-release/gz_rendering_vendor.git) | [gz-rendering](https://github.com/gazebosim/gz-rendering)   |
+| [gz_sensors_vendor](https://github.com/gazebo-release/gz_sensors_vendor.git)     | [gz-sensors](https://github.com/gazebosim/gz-sensors)       |
+| [gz_sim_vendor](https://github.com/gazebo-release/gz_sim_vendor.git)             | [gz-sim](https://github.com/gazebosim/gz-sim)               |
+| [gz_tools_vendor](https://github.com/gazebo-release/gz_tools_vendor.git)         | [gz-tools](https://github.com/gazebosim/gz-tools)           |
+| [gz_transport_vendor](https://github.com/gazebo-release/gz_transport_vendor.git) | [gz-transport](https://github.com/gazebosim/gz-transport)   |
+| [gz_utils_vendor](https://github.com/gazebo-release/gz_utils_vendor.git)         | [gz-utils](https://github.com/gazebosim/gz-utils)           |
+| [sdformat_vendor](https://github.com/gazebo-release/sdformat_vendor.git)         | [sdformat](https://github.com/gazebosim/sdformat)           |
+
+In addition to Gazebo libraries, two dependencies of Gazebo are also vendored:
+
+| Vendor Package                                                                   | External Library                                   |
+| -------------------------------------------------------------------------------- | -------------------------------------------------- |
+| [gz_dartsim_vendor](https://github.com/gazebo-release/gz_dartsim_vendor.git)     | [dartsim](https://github.com/dartsim/dart)         |
+| [gz_ogre_next_vendor](https://github.com/gazebo-release/gz_ogre_next_vendor.git) | [ogre-next](https://github.com/OGRECave/ogre-next) |
+
+**Note:** These two vendor packages are only intended to be consumed by Gazebo.
+Use of this vendor package generally (outside of Gazebo) is not recommended as
+the underlying library version might change without notice.
+
+## Using vendor packages in `package.xml`
+
+To use a Gazebo vendor package in your project, you'll need to add the
+appropriate package in your `package.xml`. For example, if you use the Gazebo
+libraries `gz-cmake`, `gz-utils` and `gz-math`, the entries in `package.xml`
+will be the following
+
+```xml
+  ...
+  <depend>gz_cmake_vendor</depend>
+  <depend>gz_utils_vendor</depend>
+  <depend>gz_math_vendor</depend>
+  ...
+```
+
+## Using vendor packages in CMake
+
+To use a Gazebo library provided by a vendor package, you'll need to
+`find_package` the vendor package and the underlying Gazebo library. Calling
+`find_package` on the vendor package indicates that the project is "buying into"
+the CMake shims provided by the vendor package. These shims make it possible to
+`find_package` the underlying library and use its CMake targets without
+including the version number in the name. Thus, when upgrading to newer versions
+of Gazebo, the project `CMakeLists.txt` file would not need to be modified.
+
+Following the example above, The CMake entry for using `gz-cmake`, `gz-utils`
+and `gz-math` will be the following:
+
+```cmake
+find_package(gz_cmake_vendor REQUIRED)
+find_package(gz-cmake REQUIRED)
+find_package(gz_utils_vendor REQUIRED)
+find_package(gz-utils REQUIRED)
+find_package(gz_math_vendor REQUIRED)
+find_package(gz-math REQUIRED)
+
+add_executable(test_gz_vendor main.cc)
+target_link_libraries(test_gz_vendor PUBLIC gz-math::gz-math gz-utils::gz-utils)
+```
+
+**Note:** The vendor packages use underscores (`_`) while the Gazebo library
+names use dashes (`-`).
+
+## Using vendor packages with binaries from packages.osrfoundation.org
+
+If you want to use a new release of Gazebo that is not officially paired with
+the release of ROS you are using (e.g. Gazebo Ionic with ROS 2 Jazzy), you can
+follow the following steps:
+
+1. Install the binaries from [packages.osrfoundation.org](packages.osrfoundation.org). Make sure to install
+   the metapackage that includes all library components (e.g. gz-ionic,
+   gz-harmonic, etc.)
+1. Clone the set of vendor packages included in
+   [gz_vendor.repos](https://gist.github.com/azeey/a94adb591475ea0e613313d3540ca451)
+   in your workspace using [vcstool](https://github.com/dirk-thomas/vcstool).
+1. Checkout the desired branch. The branch names currently track ROS 2 releases.
+   You'll need to determine the branch based on the
+   [default pairings](/docs/latest/ros_installation)
+1. Add any additional packages you need that also depend on Gazebo, such as
+   [`ros_gz`](https://github.com/gazebosim/ros_gz) and
+   [`gz_ros2_control`](https://github.com/ros-controls/gz_ros2_control/)
+1. `export GZ_RELAX_VERSION_MATCH=1`. By default, the vendor packages look for
+   an exact version match of the vendored library to be available in the system.
+   If the exact version is not found, the sources are fetched and built. This
+   environment variable causes the vendor package to match just the major
+   version number.
+1. Build the workspace
+
+## Gazebo library development with vendor packages
+
+Building the underlying packages from source might be needed when using a Gazebo
+release that is not officially paired with the ROS release you are using or when
+developing on a Gazebo library in conjunction with another ROS package that uses
+Gazebo directly. You can follow these steps to build the vendor packages from
+source:
+
+1. Clone the desired release of the Gazebo libraries into a workspace. You can
+   use a collection file from <https://github.com/gazebo-tooling/gazebodistro>
+   (e.g.
+   [`collection-harmonic.yaml`](https://github.com/gazebo-tooling/gazebodistro/blob/master/collection-harmonic.yaml))
+   with [vcstool](https://github.com/dirk-thomas/vcstool).
+1. Clone the set of vendor packages included in
+   [gz_vendor.repos](https://gist.github.com/azeey/a94adb591475ea0e613313d3540ca451)
+   in the same workspace using
+   [vcstool](https://github.com/dirk-thomas/vcstool).
+1. Checkout the desired branch. The branch names currently track ROS 2 releases.
+   You'll need to determine the branch based on the
+   [official pairings](/docs/latest/ros_installation)
+1. Add any additional packages you need that also depend on Gazebo, such as
+   [`ros_gz`](https://github.com/gazebosim/ros_gz) and
+   [`gz_ros2_control`](https://github.com/ros-controls/gz_ros2_control/)
+1. `export GZ_BUILD_FROM_SOURCE=1`. By default, the vendor packages look for an
+   exact version match of the vendored library to be available in the system. If
+   the exact version is not found, the sources are fetched and built. Also, by
+   default, the vendor packages do not depend directly on the Gazebo libraries
+   you have in your workspace. Setting this environment variable causes the
+   vendor package to match just the major version number and add dependencies on
+   the Gazebo libraries being built from source so that the correct build order
+   is followed.
+1. Build the workspace
+
+## Known Limitations
+
+- The vendor packages are currently built with Python bindings disabled
+  ([issue](https://github.com/gazebo-tooling/gz_vendor/issues/2))
+- `gz_dartsim_vendor` and `gz_ogre_next_vendor` currently always build from
+  source
+  ([gz_dartsim_vendor issue](https://github.com/gazebo-release/gz_dartsim_vendor/issues/4),
+  [gz_ogre_next_vendor issue](https://github.com/gazebo-release/gz_ogre_next_vendor/issues/4))
+- When building Gazebo libraries from source, it is not possible to build some
+  packages from source and install some packages from binaries.
+
+[^1]: https://robotics.stackexchange.com/a/93262/31574

ros_installation.md

@@ -71,6 +71,14 @@ sudo apt-get install ros-${ROS_DISTRO}-ros-gz
 This command will install the Gazebo libraries recommended for your ROS
 installation.
 
+### ROS 2 Gazebo Vendor packages
+
+As of ROS 2 Jazzy, Gazebo is available from the ROS package repository via
+vendor packages. If your package directly depends on a Gazebo library,
+instead of relying only on `ros_gz`, refer to
+[this documentation](ros2_gz_vendor_pkgs) to learn how to use the
+Gazebo vendor packages.
+
 <div class="warning">
 The rest of this document provides more information and other, alternative,
 installations pathways. We do not recommend the following approaches for new