How to log a Time Series with ROS2

Assuming you have the following file structure for your app, you first need to adjust your appauterion-app.yml file before building the app by adding a logging: key.

├── auterion-app.yml
├── Dockerfile
├── msgs_ws/
│   └── src/
│       ├── custom_msgs/
│       │   └── msg/
│               └── CustomTopic.msg
│       ├── px4_msgs/
│       │   └── msg/
│               └── VehicleOdometry.msg
│       └── std_msgs/
│           └── msg/
│               └── ColorRGBA.msg
├── README.md
├── ros_ws/
│   └── src/
│       └── fake_visual_odometry/
│           └── src/
│               └── fake_visual_odometry_node.cpp
└── settings.default.env

Auterion-app.yml Logging Key

The logging key is placed after services in your auterion-app.yml file.

auterion-api-version: 2
services:
  test-app:
    ...
logging:
  msg-paths:
  
  subscriptions: # uses the default profile
    topic:
  # Or (advanced usage)
  profiles:
    default: # profile name - can use 'verbose' profile instead
      when:
        - condition:
          subscriptions:
            topic:
          
    verbose:
          - condition:
            subscriptions:
              topic:  
  

• msg-paths: Defines where the definitions of the messages you want to log are stored. It can be a single string or a list of strings indicating file paths.

• subscriptions: Specifies which messages or topics should be logged. You can list them as simple strings or detailed objects with additional properties like logging rates.

• profiles: allows control of the logging behaviour under different conditions, and if the run conditions are met, each profile can generate its own ulog with its own logging rate and set of logged messages into a defined directory. The run conditions always, never, while-armed and while-disarmed can be used for a profile. AOS has two profiles that are already setup, default and verbose. The default profile starts logging when the system is armed. The profiles can be extended in the app configuration to include additional topic subscriptions that the logger will log. This flexibility lets you specify which messages are logged and under what conditions.

The default profile logs will be stored in /data/log/flight-stack. A new ulog is created after each arming.

The default profile is streamed to the suite. Therefore, keep the log data rate low (in the order of a few KB/s at the top).

The verbose profile would be in /data/log/flight-stack-verbose, currently disabled by default. You can change its condition to activate it.

ROS2 Logging Setup Example

The app needs to publish messages over DDS or ROS2 to log custom app data. In the auterion-app.yml for your app, you can specify the message paths and set them as subscriptions: for the AOS logger.

logging:
  # Paths to app message definitions that you want to log
  msg-paths: [msgs_ws/src/px4_msgs, msgs_ws/src/std_msgs, msgs_ws/src/custom_msgs] 

If a message doesn't contain a timestamp field, the logger will add it.

You should then be able to find the messages defined within your app auterion-app.yml file under the /data/app-config/logging/msgs after you install your app on AOS.

To log messages to the file, you just need to add ROS2 topics and ROS2 message types under subscriptions.

logging:
    subscriptions: # Default logging profile; does not log when disarmed.
        /custom_topic: custom_msgs/CustomTopic # Subscribes to a custom topic in msgs_ws/src/custom_msgs
        /test_color: std_msgs/ColorRGBA # Subscribes to a standard color message that could be publishing on the ROS 2 network.
        /fmu/in/vehicle_visual_odometry: px4_msgs/VehicleOdometry

To extend the verbose profile such that you are also logging the messages while disarmed, you would do something like this:

logging:
  # Define different logging profiles.
  profiles:
    # Extend the Default profile to add additional subscriptions and conditions.
    # Profile is defined in the logger.yml file, which is used by the data-logger.
    verbose:
      when:
        - condition: 'always'
          subscriptions:
            # Subscriptions specific to the 'always' condition.
            /custom_topic: custom_msgs/CustomTopic 
            /test_color: std_msgs/ColorRGBA
            /fmu/in/vehicle_visual_odometry: px4_msgs/VehicleOdometry 

Profile extensions will be placed in /data/app-config/logging/profiles, and logged ROS2 message definitions will be stored in /data/app-config/logging/msgs.

You could also set the logging rate for each topic by setting max_rate_hz. This is an example to log at low rate while disarmed, and full rate while armed:

    default:
      when:
        # Define behavior when the system is disarmed.
        - condition: 'while-disarmed' # Low-rate logging when disarmed.
          subscriptions:
            # Subscriptions specific to the 'while-disarmed' condition.
            /custom_topic:
              type: custom_msgs/CustomTopic # Message type for custom topic.
              max_rate_hz: 5 # Maximum logging rate in Hz.
            /test_color:
              type: std_msgs/ColorRGBA # Message type for color data.
              max_rate_hz: 5 
            /fmu/in/vehicle_visual_odometry:
              type: px4_msgs/VehicleOdometry # Message type for odometry data.
              max_rate_hz: 5 
        - condition: 'while-armed' 
          subscriptions:
            /custom_topic: custom_msgs/CustomTopic 
            /test_color: std_msgs/ColorRGBA 
            /fmu/in/vehicle_visual_odometry: px4_msgs/VehicleOdometry

Monitoring and Troubleshooting

To monitor the logging activity and troubleshoot potential issues, use:

journalctl -u data-logger -b -f

If the message is logged successfully, running journalctl -u data-logger -b -f should contain: [dds_source.cpp:111] [dds] Subscriber matched update.

Key Limitations

• Maximum Topic Size: 65536 bytes. Ensure that messages do not exceed this size to prevent logging failures.

• No Support for Dynamically-Sized Messages: Static message definitions are required due to current logging limitations.