Adapt ros2_tracing tutorial for Humble

Signed-off-by: Christophe Bedard <[email protected]>

source/Tutorials/Advanced.rst

@@ -10,6 +10,7 @@ Advanced
    Advanced/FastDDS-Configuration
    Advanced/Recording-A-Bag-From-Your-Own-Node-CPP
    Advanced/Recording-A-Bag-From-Your-Own-Node-Py
+   Advanced/ROS2-Tracing-Trace-and-Analyze
    Advanced/Reading-From-A-Bag-File-CPP
    Advanced/Simulators/Simulation-Main
    Advanced/Security/Security-Main

source/Tutorials/Advanced/ROS2-Tracing-Trace-and-Analyze.rst

@@ -0,0 +1,195 @@
+How to use ros2_tracing to trace and analyze an application
+===========================================================
+
+This tutorial shows how to use `ros2_tracing <https://github.com/ros2/ros2_tracing>`_ to trace and analyze a ROS 2 application.
+For this tutorial, the application will be `performance_test <https://gitlab.com/ApexAI/performance_test>`_.
+
+Overview
+--------
+
+This tutorial covers:
+
+1. running and tracing a ``performance_test`` run
+2. analyzing the trace data using `tracetools_analysis <https://github.com/ros-tracing/tracetools_analysis>`_ to plot the callback durations
+
+Prerequisites
+-------------
+
+This tutorial is aimed at real-time Linux systems.
+See the :doc:`real-time system setup tutorial <../Miscellaneous/Building-Realtime-rt_preempt-kernel-for-ROS-2>`.
+However, the tutorial will work if you are using a non-real-time Linux system.
+
+Installing and building
+-----------------------
+
+.. note::
+
+  This tutorial should generally work with all supported Linux distributions.
+  However, you might need to adapt some commands.
+
+Install all dependencies for ROS 2 on Linux by following the :doc:`source installation instructions <../../Installation/Alternatives/Ubuntu-Development-Setup.rst>`.
+Stop before the *Build the code in the workspace* section.
+
+Install `LTTng <https://lttng.org/docs/v2.13/>`_ and ``babeltrace``.
+
+.. code-block:: bash
+
+  sudo apt-get update
+  sudo apt-get install -y lttng-tools liblttng-ust-dev python3-lttng python3-babeltrace babeltrace
+
+Then create a workspace, import the ROS 2 {DISTRO_TITLE} code, and clone ``performance_test`` and ``tracetools_analysis``.
+
+.. code-block:: bash
+
+  cd ~/
+  mkdir -p tracing_ws/src
+  cd tracing_ws/src/
+  vcs import src/ --input https://raw.githubusercontent.com/ros2/ros2/{DISTRO}/ros2.repos
+  cd src/
+  git clone https://gitlab.com/ApexAI/performance_test.git
+  git clone https://github.com/ros-tracing/tracetools_analysis.git --branch {DISTRO}
+  cd ..
+
+Install dependencies with rosdep.
+
+.. code-block:: bash
+
+  rosdep update
+  rosdep install --rosdistro {DISTRO} --from-paths src --ignore-src -y
+
+Then build up to ``performance_test`` and configure it for ROS 2.
+See its `documentation <https://gitlab.com/ApexAI/performance_test/-/tree/master/performance_test#performance_test>`_.
+We also need to build ``ros2trace`` to set up tracing using the ``ros2 trace`` command and ``tracetools_analysis`` to analyze the data.
+
+.. code-block:: bash
+
+  colcon build --packages-up-to ros2trace ros2run tracetools_analysis performance_test --cmake-args -DPERFORMANCE_TEST_RCLCPP_ENABLED=ON
+
+Source the installation and verify that tracing is enabled:
+
+.. code-block:: bash
+
+  source install/setup.bash
+  ros2 run tracetools status
+
+You should see ``Tracing enabled`` in the output.
+This confirms that LTTng was properly detected and that the instrumentation built into the ROS 2 core is enabled.
+
+Next, we will run a ``performance_test`` experiment and trace it.
+
+Tracing
+-------
+
+Step 1: Trace
+^^^^^^^^^^^^^
+
+In one terminal, source the workspace and set up tracing.
+When running the command, a list of ROS 2 userspace events will be printed.
+It will also print the path to the directory that will contain the resulting trace (under ``~/.ros/tracing``).
+
+.. code-block:: bash
+
+  # terminal 1
+  cd ~/tracing_ws
+  source install/setup.bash
+  ros2 trace --session-name perf-test --list
+
+Press enter to start tracing.
+
+Step 2: Run Application
+^^^^^^^^^^^^^^^^^^^^^^^
+
+In a second terminal, source the workspace.
+
+.. code-block:: bash
+
+  # terminal 2
+  cd ~/tracing_ws
+  source install/setup.bash
+
+Then run the ``performance_test`` experiment (or your own application).
+We simply create an experiment with a node publishing ~1 MB messages to another node as fast as possible for 60 seconds using the second highest real-time priority so that we don't interfere with critical kernel threads.
+We need to run ``performance_test`` as ``root`` to be able to use real-time priorities.
+
+.. code-block:: bash
+
+  # terminal 2
+  sudo ./install/performance_test/lib/performance_test/perf_test -c rclcpp-single-threaded-executor -p 1 -s 1 -r 0 -m Array1m --reliability RELIABLE --max-runtime 60 --use-rt-prio 98
+
+If that last command doesn't work for you (with an error like: "error while loading shared libraries"), run the slightly-different command below.
+This is because, for security reasons, we need to manually pass ``*PATH`` environment variables for some shared libraries to be found (see `this explanation <https://unix.stackexchange.com/a/251374>`_).
+
+.. code-block:: bash
+
+  # terminal 2
+  sudo env PATH="$PATH" LD_LIBRARY_PATH="$LD_LIBRARY_PATH" ./install/performance_test/lib/performance_test/perf_test -c rclcpp-single-threaded-executor -p 1 -s 1 -r 0 -m Array1m --reliability RELIABLE --max-runtime 60 --use-rt-prio 98
+
+.. note::
+
+  If you're not using a real-time kernel, simply run:
+
+  .. code-block:: bash
+
+    # terminal 2
+    ./install/performance_test/lib/performance_test/perf_test -c rclcpp-single-threaded-executor -p 1 -s 1 -r 0 -m Array1m --reliability RELIABLE --max-runtime 60
+
+Step 3: Validate Trace
+^^^^^^^^^^^^^^^^^^^^^^
+
+Once the experiment is done, in the first terminal, press enter again to stop tracing.
+Use ``babeltrace`` to quickly look at the resulting trace.
+
+.. code-block:: bash
+
+  babeltrace ~/.ros/tracing/perf-test | less
+
+The output of the above command is a human-readable version of the raw Common Trace Format (CTF) data, which is a list of trace events.
+Each event has a timestamp, an event type, some information on the process that generated the event, and the values of the fields of the given event type.
+
+Use the arrow keys to scroll, or press ``q`` to exit.
+
+Next, we will analyze the trace.
+
+Analysis
+--------
+
+`tracetools_analysis <https://github.com/ros-tracing/tracetools_analysis>`_ provides a Python API to easily analyze traces.
+We can use it in a `Jupyter notebook <https://jupyter.org/>`_ with `bokeh <https://docs.bokeh.org/en/latest/index.html>`_ to plot the data.
+The ``tracetools_analysis`` repository contains a `few sample notebooks <https://github.com/ros-tracing/tracetools_analysis/tree/{DISTRO}/tracetools_analysis/analysis>`_, including `one notebook to analyze subscription callback durations <https://github.com/ros-tracing/tracetools_analysis/blob/{DISTRO}/tracetools_analysis/analysis/callback_duration.ipynb>`_.
+
+For this tutorial, we will plot the durations of the subscription callback in the subscriber node.
+
+Install bokeh and then open the sample notebook.
+
+.. code-block:: bash
+
+  pip3 install bokeh
+  jupyter notebook ~/tracing_ws/src/tracetools_analysis/tracetools_analysis/analysis/callback_duration.ipynb
+
+This will open the notebook in the browser.
+
+Replace the value for the ``path`` variable in the second cell to the path to the trace directory:
+
+.. code-block:: python
+
+  path = '~/.ros/tracing/perf-test'
+
+Run the notebook by clicking the *Run* button for each cell.
+Running the cell that does the trace processing might take a few minutes on the first run, but subsequent runs will be much quicker.
+
+You should get a plot that looks similar to this:
+
+.. image:: ./images/ros2_tracing_guide_result_plot.png
+  :alt: callback durations result plot
+  :align: center
+
+We can see that most of the callbacks take less than 0.01 ms, but there are some outliers taking over 0.02 or 0.03 ms.
+
+Conclusion
+----------
+
+This tutorial showed how to install tracing-related tools and build ROS 2 with tracing instrumentation.
+Then it showed how to trace a `performance_test <https://gitlab.com/ApexAI/performance_test>`_ experiment using `ros2_tracing <https://github.com/ros2/ros2_tracing>`_ and plot the callback durations using `tracetools_analysis <https://github.com/ros-tracing/tracetools_analysis>`_.
+
+For more trace analyses, take a look at the `other sample notebooks <https://github.com/ros-tracing/tracetools_analysis/tree/{DISTRO}/tracetools_analysis/analysis>`_ and the `tracetools_analysis API documentation <https://ros-tracing.gitlab.io/tracetools_analysis-api/master/tracetools_analysis/>`_.
+The `ros2_tracing design document <https://github.com/ros2/ros2_tracing/blob/{DISTRO}/doc/design_ros_2.md>`_ also contains a lot of information.