ROS 2 Logging Subsystem

• ROS 2 provides a flexible and configurable logging subsystem.
• Supports multiple logging backends.
  • stdout: Logs are printed to the standard output (default ON to console).
  • rosout: Logs are published to the /rosout topic. (default ON)
  • external: default spdlog, or your own implementation. TODAY's TOPIC

Enabling and Disabling Logging Backends

• Node option in the program. (e.g rclcpp::NodeOptions)

• Global ROS arguments via CLI. (can be overridden by NodeOptions)

  # Disabling rosout log publisher
  ros2 run foo_pkg bar_exec --ros-args --disable-rosout-logs
  
  # Disabling console output
  ros2 run foo_pkg bar_exec --ros-args --disable-stdout-logs
  
  # Disable any external loggers
  ros2 run foo_pkg bar_exec --ros-args --disable-external-lib-logs
  

Logging Severity Level

• DEBUG, INFO, WARN, ERROR and FATAL.
• A logger will only process log messages with severity at or higher than a specified level chosen for the logger.
• Logger names represent a hierarchy.
  • If the level of a logger named abc.def is unset, it will defer to the level of its parent named abc, and if that level is also unset, the global default logger level will be used. When the level of logger abc is changed, all of its descendants (e.g. abc.def, abc.ghi.jkl) will have their level impacted unless their level has been explicitly set.

For more information about ROS 2 logging...

• logging level configuration service (default OFF)
• logging level configuration via CLI
• Console output format and output colorizing
• Setting the log file name prefix
• logging environmental variables

rcl_logging_syslog

• ROS 2 rcl logging implementation built on top of syslog(3).
• Connects with rsyslog and FluentBit / etc...

Objectives

• Configure log behavior without code change.
• Multiple sink with different logging level filtering.
• Reasonable Performance.
• Log data pipeline and forward capability support.
• Enabling ROS 2 logging system with Cloud-Native Log Management and Observability.

Demo FluentBit

Demo Fluentd/Loki/Grafana

rsyslog

a.k.a rocket-fast system for log processing

rsyslog is available in default Ubuntu distribution managed by system service, performative, and many configuration supported including log data pipeline.
So that user can choose the logging configuration depending on the application requirement and use case, sometimes file system sink, sometimes forwarding to remote rsyslogd, or even FluentBit.

FluentBit

• Lightweight and Efficient: suitable for environments with limited computational power.
• High Performance: capable of handling high-volume data streams with minimal latency. It leverages asynchronous I/O and efficient data processing techniques to ensure optimal performance.
• Flexibility: supports a wide range of data sources and destinations.
• Extensibility: highly extensible through plugins including custom ones.
• Scalability: easily scaled horizontally to handle increasing data volumes by deploying multiple instances.
• Reliability: features like fault tolerance and retry mechanisms to ensure data reliability.

How to use

export RCL_LOGGING_IMPLEMENTATION=rcl_logging_syslog
colcon build --symlink-install --cmake-clean-cache --packages-select rcl_logging_syslog rcl

• The pain is we always need to build for now... we cannot choose the external logger at runtime...
• Feature Request: Select the logger without rebuilding, hopefully i could fix this in next release
• If you use docker, either binding -v /dev/log:/dev/log or enable rsyslogd in the container.

Issues and PRs always welcome

source code, documentation, presentation slides, everything is here.

https://github.com/fujitatomoya/rcl_logging_syslog