Feature request

Feature description

Ability to configure logging level externally at runtime.

In the future there will be a generalized approach to external configuration of loggers at runtime

see https://docs.ros.org/en/rolling/Tutorials/Demos/Logging-and-logger-configuration.html#logger-level-configuration-externally

Requirements

• ROS 2 application (including ros2cli) can change the logging level for specific node during runtime.
• Node developer can opt-in this option via Node:Options. (in default, this is disabled.)
• Node is only be able to set the logging level of logger name that belongs to that node process space.

Implementation Consideration

• GUI tools are not in scope of this issue, this is dedicated to node interface.
• Expose additional service for each node to set and get the logging level of logger name at runtime.
  • service path: /nodename/get_logger_level and /nodename/set_logger_level.
• This could be one of the Node::Options that user opt-in if they want to. Since this is debug feature and adding extra service, this should not be opt-out.
• If using components node, requesting to change logger level to Node-A would be effectively changing logger level in Node-B.
  • This is because that logger level hash map is maintained by in the process space.
  • logger names and levels are maintained agnostic from node configuration, logging level will be applied once the corresponding node is created.
• Not only for setting the logging level, but also user should be able to know the current logging level via service?
  • Probably yes, it is likely that user application might want to check the current logging level during runtime.
  • rcl_create_node_logger_name is internally issued and creates logger name for that node, but user application can create other rclcpp::Logger if needed.
• ROS 2 system debugging level should be accepted as well by default, such as rclcpp, rcl and rclpy.
  • This could be really useful to debug ROS 2 core system during application running.
• This feature requires service file must have the field to specify the logger_name and logger_level.
• Supporting user callback to be called on service request?
  • Probably no, what is the actual use case for this?

Sample Demo

• https://github.com/ros2/demos/blob/rolling/logging_demo/src/logger_config_component.cpp

Tasks

• rcl_interfaces Add interfaces for logging service. rcl_interfaces#154
• rclcpp Add support for logging service. rclcpp#2122
• rclpy Logging service support rclpy#1102
• demos Add demos for using logger service demos#611
• ros2_documentation Add logger service description ros2_documentation#3477
• Iron Release Note External configuration services of logger for Iron Release. ros2_documentation#3478