Bringing Linux pidfd to Ruby

In the presentation titled 'Bringing Linux pidfd to Ruby' at RubyKaigi 2025, Maciej Mensfeld discusses the challenges of process and fork management in Ruby, which traditionally relies on Process IDs (PIDs). He notes that this can lead to race conditions and security vulnerabilities, particularly in high-throughput systems. The talk highlights the introduction of pidfd in Linux 5.3, which provides a more reliable method for managing processes than conventional PIDs, but notes the absence of native Ruby support for pidfd.

Key Points Discussed:
- Introduction to the Problem:
- Maciej emphasizes the difficulties that arise in Ruby when using PIDs for process management, such as PID reuse leading to potential errors and race conditions when managing child processes.
- He mentions specific challenges like signal race conditions and difficulties with tracking process trees, common issues when processes continue to fork and manage workload in multi-threaded environments.

Pidfd as a Solution:
- Introduced in Linux 5.3, pidfd utilizes file descriptors for referencing processes, reducing issues such as PID reuse and allowing for more stable signal handling. It allows reliable and non-blocking monitoring of process states.
- The speaker elaborates on how pidfd's design eliminates many of the race conditions typically seen with PID management.
Implementation in Ruby with FFI:
- Lacking native support, Mensfeld demonstrates how he used Foreign Function Interface (FFI) in Ruby to construct an abstraction over the pidfd APIs, thus incorporating these features into Ruby applications like Karafka and Shyuken.
- He explains the challenges and successes in adapting these features, including how to handle system call mappings and manage child processes effectively.
Lessons Learned:
- Mensfeld emphasizes the complexity of robust process management and acknowledges the importance of utilizing the right tools and APIs to avoid security pitfalls in Ruby applications.
- He expresses his intent to extract his findings into a standalone Ruby gem to help others implement these practices in their work.

Conclusion:
Mensfeld wraps up by reflecting on the need for Ruby to evolve and better support modern Linux features. He encourages the Ruby community to embrace these tools for improved reliability and security in process management. The presentation showcases both the technical depth required to manage processes efficiently in Ruby and the innovative approaches developers can take to overcome existing limitations.

Overall, attendees gained insights into advanced process management strategies using modern Linux features, enhancing the stability and security of Ruby applications managing concurrent processes.

Bringing Linux pidfd to Ruby
Maciej Mensfeld • Matsuyama, Ehime, Japan • Talk

Date: April 16, 2025
Published: May 27, 2025
Announced: unknown

Processes and fork management in Ruby have traditionally relied on PIDs, leading to race conditions and potential security issues in high-throughput systems. While Linux 5.3 introduced pidfd as a solution, Ruby lacks native support for this feature. I'll demonstrate how I bridged this gap using FFI, exploring syscall mappings, zombie process prevention, and practical process management patterns. Through live demonstrations, you'll learn how Linux pidfd APIs can help you eliminate race conditions and make your Ruby applications more reliable in modern environments.

https://rubykaigi.org/2025/presentations/maciejmensfeld.html

RubyKaigi 2025