Eventlet Removal PTG Retrospective - Gazpacho to Hibiscus

Gazpacho Retrospective 🔗

The Gazpacho cycle marked a period of significant progress in the eventlet removal initiative, with foundational work completed in core libraries and substantial advances across multiple OpenStack projects. The session began with updates from the eventlet library itself and Oslo services, which provide critical infrastructure for the broader migration effort.

Project-by-Project Progress 🔗

The Gazpacho cycle saw remarkable progress across the OpenStack project landscape, with three projects achieving complete migration away from eventlet and many others making substantial advances toward threading-based concurrency. The migration efforts varied in approach, with some projects opting for gradual service-by-service transitions while others pursued comprehensive migrations. This diversity in strategies has provided valuable lessons for the community.

✅ Completed Migrations

Three projects reached the significant milestone of completing their eventlet removal during the Gazpacho cycle, joining the ranks of earlier pioneers like Octavia, Mistral, and Ironic. These successes demonstrate that full migration is achievable across different types of OpenStack services:

🟢 Significant Progress

Several major OpenStack projects have made substantial progress in their migrations, with many services already running in threading mode by default. These projects represent the bulk of the community's migration effort and are demonstrating various successful approaches to the transition. Nova's gradual service-by-service strategy and Manila's performance validation framework stand out as particularly valuable contributions:

🟡 In Progress

Swift continues its migration journey with impressive test coverage already achieved. The project faces unique technical challenges related to erasure coding that require careful consideration of concurrency behavior. The team is working through these challenges systematically while maintaining the high reliability standards Swift operators expect:

Call to Action for Hibiscus 🔗

Building on the momentum established during Gazpacho, the Hibiscus cycle represents a critical phase in the eventlet removal initiative. The focus shifts from initial migration work to defaulting projects to threading mode, expanding test coverage to include Python 3.14, and addressing remaining technical blockers. The community has identified five primary goals that will guide the work throughout this cycle, along with a clear migration timeline strategy that balances progress with stability.

Concerns and Noticed Problems 🔗

While significant progress has been made, the PTG session identified several technical challenges that require attention during the Hibiscus cycle and beyond. These issues range from critical blockers that could affect Python version compatibility to medium-priority concerns about library dependencies and testing infrastructure. Understanding and addressing these challenges is essential for maintaining the migration timeline and ensuring stable deployments.

🔴 Critical Issues

Three critical issues emerged that require immediate attention. These problems have the potential to block progress on Python version upgrades or affect multiple projects simultaneously. The community is actively working on solutions, but these challenges represent the highest priority concerns for the Hibiscus cycle:

🟡 Medium Priority Issues

Beyond the critical blockers, several medium-priority issues were identified that affect code quality, test coverage, and operator experience. While these don't immediately block the migration, they represent technical debt that should be addressed to ensure a smooth transition and maintain long-term code maintainability:

🟣 Architectural Concerns

Looking beyond immediate technical issues, the community discussed longer-term architectural questions about the future of concurrency in OpenStack. These concerns don't require immediate action but represent important strategic considerations that will shape the project's evolution after eventlet is fully removed:

Performance Testing Insights 🔗

One of the most significant achievements during the Gazpacho cycle was the development of performance testing frameworks that provide concrete data about the impact of migrating from eventlet to native threading. These insights have been crucial in building confidence that the migration can be completed without significant performance degradation. Different projects have encountered varying challenges based on their specific workload characteristics and architectural patterns.

Notable Achievements 🔗

The Gazpacho cycle delivered several significant milestones that demonstrate the viability and momentum of the eventlet removal initiative. These achievements span complete project migrations, successful default switching to threading mode, development of reusable testing infrastructure, and validation of performance parity. The successes provide both concrete progress and valuable lessons that benefit the entire community.

Next Steps Summary 🔗

The eventlet removal initiative follows a phased timeline that balances aggressive progress with operational stability. The roadmap is organized into three time horizons: immediate actions for the Hibiscus cycle, medium-term objectives targeting the 2027.1 release, and long-term goals for 2027.2 and beyond. This structured approach ensures that the community maintains momentum while giving operators adequate time to adapt their deployments and providing fallback options during the transition.

Resources

The eventlet removal initiative maintains several resources to support contributors and track progress. These include session recordings and notes from PTG discussions, official documentation and governance materials, and development tracking tools. The community encourages all stakeholders to engage through these channels to stay informed and contribute to the effort.

Conclusion