Massive performance improvements and cleaner shutdown

[botbench]

Tight while() loop in main() now uses rclpp::Rate to reduce CPU usage due to busy waiting.
Node now catches both SIGINT and TERM and passes off shutdown to handler.
CPU usage has gone from 100% of one core to around 1-3%.

[gemini-code-assist]

Hello @botbench, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

Summary of Changes

This pull request addresses performance issues and improves the shutdown process of the laser scan publisher node. It introduces a rclcpp::Rate to control the loop frequency, reducing CPU usage. Additionally, it implements signal handling for SIGINT and SIGTERM to ensure a graceful shutdown. A cleanup function is also registered to be called on shutdown.

Highlights

• Performance Improvement: Implements rclcpp::Rate to regulate the main loop's frequency, significantly reducing CPU usage from 100% to 1-3%.
• Graceful Shutdown: Adds signal handling for SIGINT and SIGTERM signals, triggering a cleanup function and proper shutdown of the node.
• Cleanup Function: Registers a cleanup function (node_cleanup) using rclcpp::on_shutdown to perform necessary actions before the node terminates.

Changelog

• src/main.cpp
  • Introduces shutdown_requested atomic boolean to control the main loop's execution.
  • Adds signal_handler function to catch SIGINT and SIGTERM signals and initiate shutdown.
  • Implements node_cleanup function to perform cleanup tasks before shutdown.
  • Registers signal_handler for SIGINT and SIGTERM signals.
  • Registers node_cleanup function to be executed on shutdown.
  • Replaces the tight while loop with a loop that uses rclcpp::Rate to control the frequency.
  • Adds a check for shutdown_requested in the main loop condition.
  • Closes the command port (cmd_port.Close()) after the loop finishes.

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A node's gentle sleep,
No longer a CPU hog,
Signals bring it rest.

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[gemini-code-assist]

Code Review

This pull request introduces significant performance improvements by reducing CPU usage and implementing a cleaner shutdown process. The changes include using rclcpp::Rate to control the loop frequency and handling SIGINT and SIGTERM signals for graceful shutdown. Overall, the changes seem well-structured and address the stated goals effectively.

Summary of Findings

• Signal Handler and Shutdown: The signal handler and shutdown mechanism are well-implemented, ensuring a graceful shutdown of the node upon receiving SIGINT or SIGTERM signals. This prevents abrupt termination and allows for proper resource cleanup.
• Rate Limiting: The use of rclcpp::Rate effectively reduces CPU usage by preventing a tight loop. Setting the rate to 40Hz seems reasonable for most cases, but it might be beneficial to allow this value to be configurable via a parameter.
• Resource Cleanup: The addition of cmd_port.Close() ensures that the serial port is properly closed before the node terminates, preventing potential resource leaks or conflicts.

Merge Readiness

The pull request is well-structured and addresses the performance and shutdown issues effectively. The changes significantly reduce CPU usage and provide a cleaner shutdown process. I recommend merging this pull request after addressing the comments below. I am unable to directly approve the pull request, and users should have others review and approve this code before merging.

[GyuH13]

@botbench
Thank you for your contribution. We will discuss the relevant part and make modifications as necessary before applying it. This PR will be closed. Thank you!

[botbench]

Great! I am working on some other improvements to the driver. I'll post that pull request soon.

[GyuH13]

Hello @botbench
#27 (comment)
Thank you for your contribution!
By adding sleep to the infinite while loop, we were able to reduce the CPU usage from 100% to around 5%.
I’ve added your PR as a reference in the ChangeLog. Thanks again!