Postgres LISTEN/NOTIFY Proven Scalable
Global locking issue overcome to achieve 60K writes per second
1Postgres NOTIFY's bad reputation
Postgres's LISTEN/NOTIFY feature was infamous for not scaling due to global locking. While this perception spread through a popular blog post, it's now proven that with proper optimizations, the system can deliver high performance. This is particularly crucial for applications requiring real-time data streaming.
2Core challenge in stream-based architecture
The main difficulty in data streams is how to alert readers when new data arrives. Continuous polling consumes resources and causes latency. LISTEN/NOTIFY offers a more efficient solution but introduces its own performance barriers that need addressing.
3Impact of global locking
Postgres uses a global mutex that locks the entire system during NOTIFY operations. This creates severe bottlenecks in high-volume write scenarios. Benchmarks showed it was impossible to exceed 2,900 write operations per second due to this lock.
4Notification buffering solution
The developed solution buffers NOTIFY notifications in memory and processes them in batches periodically. This approach reduces the global lock's impact by 90%, enabling 60,000 write operations per second. Buffering also allows leveraging Postgres's group commit feature.
5Maintaining order guarantees
The buffering method maintains notification order guarantees while improving performance. For crash resilience, it integrates with WAL (Write-Ahead Logging) mechanism. This achieves high throughput without data loss risks.
6Game-changer for real-time systems
This optimization makes Postgres viable for various real-time applications from chat platforms to financial transaction monitoring. It enables low-latency streams while preserving the database's durability and consistency advantages.
Original article: Hacker News — Postgres LISTEN/NOTIFY ölçeklenebilirliği kanıtlandı