Log from your code

The stack logs through core_logger, not through RCLCPP_*, printf or std::cout. One logger means one place to set levels, one format, and output that reaches both the console and rosout.

Note

core_utils is the deliberate exception — it sits below the logger and cannot depend on it.

Basic use

#include <core_logger/log.hpp>

LOG_INFO("arm enabled");
LOG_INFO_STREAM("moving to destination " << destination);
LOG_WARN_STREAM("retrying after " << delay_s << " s");
LOG_ERROR_STREAM("plan failed: " << ErrorCodes::ToString(code));

Levels, quietest to loudest: FATAL, ERROR, WARN, INFO, DEBUG, VERBOSE. Each has a plain and a _STREAM form, and a _NAMED / _STREAM_NAMED variant that takes an explicit logger name.

Set the level at runtime:

CORE_LOG_LEVEL=VERBOSE ros2 launch <app>_bringup <app>.launch.py

Choosing a level

The test is who reads the line and how often it fires.

Level	Use for
`ERROR`	The operation failed and the caller must handle it.
`WARN`	Something unexpected that the system recovered from. Not for outcomes that are routine — a planner returning “start and goal too close” when the arm is already at the goal is expected, and belongs at `INFO`.
`INFO`	Milestones an operator would want in a normal run. One line per phase, not per trajectory point.
`DEBUG`	Detail for diagnosing a specific subsystem.
`VERBOSE`	Per-iteration and per-message detail, including protocol traffic.

Warning

Anything that fires per trajectory point or per network message belongs at VERBOSE. A per-point INFO line makes the console unusable and hides the lines that matter.

In headers

The bare LOG_* macros do not work in a header that is included from another package. They resolve ::logger, a non-dependent name that may not exist at the include site. Use the _NAMED form and pass the logger explicitly:

// in a header
LOG_INFO_STREAM_NAMED("my_component", "value: " << value);

Inside ROS nodes

core_logger’s RclutilsAppender bridges log output onto rosout, so ros2 topic echo /rosout and Foxglove see the same lines as the console.

Warning

Detach the appender before the node shuts down or the plugin unloads. dlclose on a plugin and rclcpp shutdown both segfault the host process if an attached appender outlives the context it writes to.

ScopedRootLogger handles this — it attaches on construction and detaches on destruction. Prefer it to attaching by hand.

Checking your work

Before opening a PR, confirm nothing slipped back in:

grep -rnE 'RCLCPP_(INFO|WARN|ERROR|DEBUG|FATAL)|printf\(|std::cout' \
  --include=*.cpp --include=*.hpp src/ | grep -v core_utils