THIS IS WORK IN PROGRESS AND SHOULD BE USED WITH CARE
Repository for implementing rosbag2 as described in its corresponding design article
rosbag2 packages are available via debian packages and thus can be installed via
$ sudo apt-get install ros2bag* rosbag2*
For other platforms than Linux, rosbag2 has to be built from source as it's currently not part of the latest (ros2.repos file)[https://github.com/ros2/ros2/blob/master/ros2.repos].
Build from source
It is recommended to create a new overlay workspace on top of your current ROS 2 installation.
$ mkdir -p ~/rosbag_ws/src $ cd ~/rosbag_ws/src
Clone this repository into the source folder:
$ git clone https://github.com/ros2/rosbag2.git
Then build all the packages with this command:
$ colcon build [--merge-install]
--merge-install flag is optional and installs all packages into one folder rather than isolated folders for each package.
The tests can be run using the following commands:
$ colcon test [--merge-install] $ colcon test-result --verbose
The first command executes the test and the second command displays the errors (if any).
rosbag2 is part of the ROS 2 command line interfaces.
This repo introduces a new verb called
bag and thus serves as the entry point of using rosbag2.
As of the time of writing, there are three commands available for
In order to record all topics currently available in the system:
$ ros2 bag record -a
The command above will record all available topics and discovers new topics as they appear while recording.
This auto-discovery of new topics can be disabled by given the command line argument
To record a set of predefined topics, one can specify them on the command line explicitly.
$ ros2 bag record <topic1> <topic2> … <topicN>
The specified topics don't necessarily have to be present at start time.
The discovery function will automatically recognize if one of the specified topics appeared.
In the same fashion, this auto discovery can be disabled with
If not further specified,
ros2 bag record will create a new folder named to the current time stamp and stores all data within this folder.
A user defined name can be given with
After recording data, the next logical step is to replay this data:
$ ros2 bag play <bag_file>
The bag file is by default set to the folder name where the data was previously recorded in.
The recorded data can be analyzed by displaying some meta information about it:
$ ros2 bag info <bag_file>
You should see something along these lines:
Files: demo_strings.db3 Bag size: 44.5 KiB Storage id: sqlite3 Duration: 8.501s Start: Nov 28 2018 18:02:18.600 (1543456938.600) End Nov 28 2018 18:02:27.102 (1543456947.102) Messages: 27 Topic information: Topic: /chatter | Type: std_msgs/String | Count: 9 | Serialization Format: cdr Topic: /my_chatter | Type: std_msgs/String | Count: 18 | Serialization Format: cdr
Storage format plugin architecture
Looking at the output of the
ros2 bag info command, we can see a field called
rosbag2 specifically was designed to support multiple storage formats.
This allows a flexible adaptation of various storage formats depending on individual use cases.
As of now, this repository comes with two storage plugins.
The first plugin, sqlite3 is chosen by default.
If not specified otherwise, rosbag2 will store and replay all recorded data in an SQLite3 database.
Secondly, rosbag2 provides support for legacy ROS 1 bag data. TODO(karsten1987) Add link when rosindex ran.
In order to use a specified (non-default) storage format plugin, rosbag2 has a command line argument for it:
$ ros2 bag <record> | <play> | <info> -s <sqlite3> | <rosbag2_v2> | <custom_plugin>
Have a look at each of the individual plugins for further information.
Serialization format plugin architecture
Looking further at the output of
ros2 bag info, we can see another field attached to each topic called
By design, ROS 2 is middleware agnostic and thus can leverage multiple communication frameworks.
The default middleware for ROS 2 is DDS which has
cdr as its default binary serialization format.
However, other middleware implementation might have different formats.
If not specified,
ros2 bag record -a will record all data in the middleware specific format.
This however also means that such a bag file can't easily be replayed with another middleware format.
rosbag2 implements a serialization format plugin architecture which allows the user the specify a certain serialization format. When specified, rosbag2 looks for a suitable converter to transform the native middleware protocol to the target format. This also allows to record data in a native format to optimize for speed, but to convert or transform the recorded data into a middleware agnostic serialization format.
By default, rosbag2 can convert from and to CDR as it's the default serialization format for ROS 2.