reload

Hot Reload Example

This example demonstrates cross-platform configuration hot reloading using FileWatchSource.

What It Does

• Watches config.json for changes
• Automatically reloads configuration when the file is saved
• No restart required — the application continues running
• Works on Windows, Linux, and macOS

Running the Example

cd examples/reload
go run main.go

You should see:

=== Hot Reload Example (Cross-Platform) ===

✅ Configuration loaded: {AppName:LifecycleDemo Debug:true Port:8080 Message:Hello from lifecycle hot reload!}

✨ App started with hot reload enabled!
   Edit config.json to see configuration reload in real-time
   Press Ctrl+C to exit

📊 LifecycleDemo running on port 8080 (debug=true): Hello from lifecycle hot reload!

Testing Hot Reload

While the app is running, edit config.json:

{
  "app_name": "MyAwesomeApp",
  "debug": false,
  "port": 9000,
  "message": "Configuration updated without restart!"
}

Save the file, and you'll immediately see:

🔄 Config file changed!

✅ Configuration loaded: {AppName:MyAwesomeApp Debug:false Port:9000 Message:Configuration updated without restart!}

📊 MyAwesomeApp running on port 9000 (debug=false): Configuration updated without restart!

Technical Details

FileWatchSource

Uses fsnotify library for efficient, event-driven file watching:

• Linux: Uses inotify
• Windows: Uses ReadDirectoryChangesW
• macOS/BSD: Uses kqueue

Thread-Safe Configuration

Configuration updates use sync.RWMutex:

• Write lock during reload (exclusive)
• Read lock during access (shared)
• Ensures atomic configuration swaps

Comparison: FileWatch vs SIGHUP

Verdict: FileWatch is superior for configuration hot reload.

Related Examples

• control: Webhook-triggered reload (HTTP POST /reload)
• supervisor: Worker restart patterns

Note: For production use, consider adding:

• Configuration validation before applying
• Rollback on invalid config
• Audit logging of config changes