Swift Service Discovery

Yim Lee from Apple's Swift team just open-sourced a game-changer for server-side Swift. If you're building microservices, this standardized approach to service discovery could save you from vendor lock-in.

Apple released Swift Service Discovery, a new open-source package that defines a standard API for service discovery in Swift server applications. Similar to SwiftLog and SwiftMetrics, it provides the interface while backend implementations (DNS-based, key-value stores, etc.) handle the actual functionality.

Key Takeaways

• Defines standard API for service discovery, not tied to specific backends
• Two core methods: lookup for one-time queries, subscribe for real-time updates
• Subscribe returns CancellationToken for managing long-lived service instance monitoring
• Backend implementations must conform to ServiceDiscovery protocol with deadline support
• Community-driven project actively seeking backend implementation contributions

The subscribe pattern's approach to handling service instance changes reveals an interesting design choice about push vs. pull architectures.