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Get logging output to /rosout using rclutils (writing a client library)

asked 2021-03-08 07:19:02 -0500

Jan Wielemaker
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I'm writing a ROS2 client library for SWI-Prolog. Basic pub/sub works. Next step is to get logging to work. Calling rcutils_log() works fine for loging to the console, but nothing appears in /rosout or in rqt. It doesn't seem to matter whether I leave the initialization to RCUTILS_LOGGING_AUTOINIT or call rcutils_logging_initialize(). Controlling the level affects the output in the console, so the basics seem to work. I tried with and without a creating a ROS node. The subscription works fine and the node is visible in rqt.

Platform is Ubuntu 20.04 using ROS2 foxy.

Any clue, including clues on how to debug this?

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answered 2021-03-08 13:36:51 -0500

Jan Wielemaker
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After a lot of searching in the rcl and rcutils sources and some gdb breakpoints, I got it working. Key are

Initialize logging right after creating the rcl context, notably __before__ creating a node in this context.
Use rcl_logging_configure_with_output_handler() with rcl_logging_multiple_output_handler as handler, also __before__ creating a node.
Make sure options.enable_rosout is true for rcl_node_init(). This is by default the case, but it was set to false in my code based on rclpy (which I guess sets it somewhere else).

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This is probably rather niche, but thanks @Jan Wielemaker for posting the solution. Saved my quite a bit of time.

gvdhoorn ( 2022-08-12 07:03:04 -0500 )edit

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Asked: 2021-03-08 07:19:02 -0500

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Last updated: Mar 08 '21

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Get logging output to /rosout using rclutils (writing a client library)