Text log splitting / rotation in ROS 2

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Hi,

Re. your fist question:

I think the link you mention might be ROS 2 python only. There is currently no rotating log functionality for c++, though it could probably be added without too much effort:

If you are using c++, logging is configured from rclcpp::init(), which ultimately calls rcl_logging_external_initialize, see here.

External logging uses the spdlog library. The logger is created here. Spdlog supports rotating log files, so if you change logger creation to something similar to this, you should have rotating log files.

That would obviously be a local hack, and you need to compile ROS 2 from source. To make this into a full feature, one should:

• File an issue in the rcl_logging repository to discuss the best option to configure this (environment variable / command line argument / configuration file / other?),

• In case of a configuration file: first check if there are existing implementations, e.g. this, and discuss whether it would be best to use these or to implement something custom (e.g. to avoid an extra dependency).

• Change accordingly:

  • For environment variable: add to rcl_logging_external_initialize similar to this code,
  • For command line argument: add to rcl_parse_arguments, see code documentation here,
  • For logfile: add implementation here.

Given you state that this request has "been existing already for years" and it being "really an issue", maybe you should give it a go? :-) It shouldn't be ultimately difficult nor time-consuming, given above info.

Possible alternative solution

• Disable external logging through the environment variable (refer to the docs),
• Have something read the /rosout topic and write it to file,
  • I think rosbag could be used, though files are not in .csv by default, see here for info wrt conversion.
• Write a script to restart your reader whenever you want the logfile to rotate.
• This has the benefit of being a process-agnostic logger (i.e. gathers all log info of all nodes in a ROS 2 network, instead of having one log file per process),
• It does not contain log info from non-node loggers (the ones created by rclcpp::get_logger("name")), only messages from node loggers (node->get_logger()).

Re. your 2nd question:

You can specify loglevels on a per-name basis, e.g.:

ros2 run package node --ros-args --log-level DEBUG --log-level rcl:=INFO --log-level rclcpp:=INFO

This sets default loglevel to DEBUG, but disables anything below INFO for rcl and rclcpp.