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ROS Bag Recording

ROS bags are the primary method for recording data during robot operation. They capture ROS 2 topics for later analysis, debugging, and algorithm development.

Overview

ROS bag recording in AirStack:

  • Automatic recording via bag_recorder_pid package
  • Selective topic recording to manage storage
  • Integration with logging infrastructure
  • Support for onboard and offboard recording

Quick Start

Manual Recording

Record specific topics: 

ros2 bag record /robot1/odometry /robot1/camera/image_raw

Record all topics: 

ros2 bag record -a

Record with storage limit: 

ros2 bag record -a --max-bag-size 1000  # 1GB per file

Automatic Recording

AirStack can automatically record bags using the bag_recorder_pid package.

Configure in the robot launch files to automatically start recording when the autonomy stack launches.

Configuration

Topic Selection

Choose topics based on mission objectives:

Minimal set (state and commands): 

topics:
  - /{robot_name}/odometry
  - /{robot_name}/global_plan
  - /{robot_name}/trajectory_controller/trajectory_segment_to_add

Standard set (add sensor data): 

topics:
  - /{robot_name}/odometry
  - /{robot_name}/global_plan
  - /{robot_name}/camera/image_raw/compressed
  - /{robot_name}/depth/image_raw
  - /{robot_name}/imu/data

Full set (everything for debugging): 

topics:
  - ".*"  # Record all topics

Storage Management

On resource-constrained platforms (Jetson, VOXL):

  • Limit bag size: Use --max-bag-size to split large bags
  • Selective recording: Only record topics needed for mission
  • Compression: Use compressed image topics when available
  • Automatic offload: Configure data offloading to free space

Storage Locations

Development (Docker)

  • Bags stored in mounted volume: robot/bags/
  • Persists across container restarts

Hardware Deployment

  • Default location: /opt/airstack/bags/ or local SSD
  • Configure via environment variable: ROSBAG_DIR

Playback and Analysis

Basic Playback

Play back a recorded bag: 

ros2 bag play path/to/bagfile

Play at different speed: 

ros2 bag play path/to/bagfile --rate 0.5  # Half speed

Play in loop: 

ros2 bag play path/to/bagfile --loop

Bag Information

Get bag metadata: 

ros2 bag info path/to/bagfile

Example output: 

Files:             rosbag2_2024_03_17-14_30_00.db3
Bag size:          1.2 GB
Storage id:        sqlite3
Duration:          300.5s
Start:             Mar 17 2024 14:30:00.123
End:               Mar 17 2024 14:35:00.623
Messages:          45123
Topic information:
  Topic: /robot1/odometry | Type: nav_msgs/msg/Odometry | Count: 3005 | Serialization Format: cdr
  Topic: /robot1/camera/image_raw/compressed | Type: sensor_msgs/msg/CompressedImage | Count: 1500 | Serialization Format: cdr
  ...

Extract Specific Topics

Convert to a new bag with only specific topics: 

ros2 bag filter input_bag -o output_bag --topics /robot1/odometry /robot1/camera/image_raw

Common Workflows

Debug Mission Issues

  1. Record full topic set during mission
  2. Play back locally in simulation
  3. Analyze behavior with rviz or custom tools
  4. Iterate on algorithms offline

Algorithm Development

  1. Record sensor data in real environment
  2. Play back during development
  3. Test new algorithms against real data
  4. Validate before hardware deployment

Performance Analysis

  1. Record timestamped topics
  2. Analyze latencies and frequencies
  3. Identify bottlenecks
  4. Optimize performance

Best Practices

  • Test recording setup before important missions
  • Monitor disk space during operation
  • Use compression for image topics
  • Document bag contents with descriptive names
  • Archive important bags with mission metadata
  • Regular cleanup of old/unnecessary bags

Troubleshooting

Bag recording fails to start:

  • Check disk space availability
  • Verify write permissions to bag directory
  • Check if bag_recorder_pid is running

Bags too large:

  • Use topic filtering to record only necessary data
  • Enable compression for image topics
  • Use --max-bag-size to split files
  • Consider reducing sensor publishing rates

Playback issues:

  • Ensure ROS 2 version matches recording system
  • Check topic names and types match expectations
  • Verify clock synchronization settings

Missing data in bags:

  • Verify topics were being published during recording
  • Check bag info to confirm topics recorded
  • Ensure recording started before mission began

Integration with Data Offloading

For automatic transfer of bags from robot to ground station or storage server:

See: Data Offloading Guide

See Also