hot-reload

🔥 Hot-reload Example (Dynamic Loading)

This example demonstrates how to update your engine's business logic (rules) in real-time without restarting the application or recompiling the code.

Concepts Illustrated

1. Snapshotting & Thread-safety

The Engine is protected by a sync.RWMutex. When an evaluation (Run) is launched, it uses a snapshot of the current rules. If an update occurs during execution, it will only affect subsequent evaluations, ensuring total consistency.

2. HTTPRuleProvider

A provider that retrieves rules in JSON format via a URL. It intelligently handles HTTP headers:

• ETag: To avoid reloading data if it hasn't changed on the server.
• Context support: For clean request cancellation.

3. HotReloader

A manager that performs polling (periodic checks) at a defined interval and automatically updates the Engine if new rules are detected.

How the example works

1. A local HTTP server is launched to simulate a rules API.
2. The server first serves Version 1 of a rule ("rule-v1").
3. The reloader detects the rule and updates the Engine.
4. The Engine evaluates the facts and triggers the event for "rule-v1".
5. The server changes its response to Version 2.
6. The reloader detects the change and performs a transparent "hot-swap".
7. The next evaluation automatically uses "rule-v2".

Execution

go run main.go