Introduction
ros2 bag is a command line tool for recording data published on topics in your system. It accumulates the data passed on any number of topics and saves it in a database. You can then replay the data to reproduce the results of your tests and experiments. Here are some common CLI actions:
- To record:
ros2 bag record -o MyOutputBag /turtle1/cmd_vel /turtle1/pose
- To check bag information:
ros2 bag info MyOutputBag
Ros Bag Recording From a Node
Here is an example from the ROS2 website
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import rclpy
from rclpy.node import Node
from rclpy.serialization import serialize_message
from std_msgs.msg import String
import rosbag2_py
class SimpleBagRecorder(Node):
def __init__(self):
super().__init__('simple_bag_recorder')
self.writer = rosbag2_py.SequentialWriter()
storage_options = rosbag2_py._storage.StorageOptions(
uri='my_bag',
storage_id='sqlite3')
converter_options = rosbag2_py._storage.ConverterOptions('', '')
self.writer.open(storage_options, converter_options)
topic_info = rosbag2_py._storage.TopicMetadata(
name='chatter',
type='std_msgs/msg/String',
serialization_format='cdr')
self.writer.create_topic(topic_info)
self.subscription = self.create_subscription(
String,
'chatter',
self.topic_callback,
10)
self.subscription
def topic_callback(self, msg):
self.writer.write(
'chatter',
serialize_message(msg),
self.get_clock().now().nanoseconds)
def main(args=None):
rclpy.init(args=args)
sbr = SimpleBagRecorder()
rclpy.spin(sbr)
rclpy.shutdown()
if __name__ == '__main__':
main()
SequentialWriterwrites messages by the order they are received
By default, ROS 2 bag files use SQLite3 as the storage backend. However, ROS 2 supports different storage formats (e.g., MCAP) depending on the plugin being used. The default storage format is sqlite3: ros2 bag record -s sqlite3 /imu_data /scan. The recorded data is stored as an SQLite database file (*.db) inside the bag directory.
One can even synthesize bag data and does not create ros topics
