suspend/

README

Suspend/Resume Example (The Factory)

This example demonstrates a complex, stateful application (a "Factory") that can be Suspended and Resumed without losing data.

It showcases:

• State Persistence: Saving/Loading JSON state on suspend/resume.
• Worker Coornidation: Coordinating multiple workers (Generator, Worker, Watchdog).
• Smart Signal Handling: Using Ctrl+C to trigger Suspend instead of immediate Exit.

🎮 Controls

• s: Suspend the factory via input.
• r: Resume production via input.
• Ctrl+C (1st): Tries to Suspend gracefully (Escalation Mode).
• Ctrl+C (2nd): Force Exit (Immediate Kill).
• q: Quit gracefully via input.

🛡️ Safety Net Pattern

This example uses the Safety Net Pattern for signal handling:

• 1st Ctrl+C: Tries to Suspend gracefully.
• 2nd Ctrl+C: Force Exit (Immediate Kill).

This ensures that even if the Suspend logic hangs, you can always force-quit the application by mashing Ctrl+C.

📁 Project Structure

• shared/: Common logic (persistence, shared workers, factory runner).
• cond/: Implementation using sync.Cond. Best for legacy code or simple wait/signal requirements.
• channels/: Implementation using channels and select. Idiomatic v1.5+ style, highly composable and better integration with Go's concurrency model.

🚀 Running

To run the idiomatic channel-based version:

go run ./examples/suspend/channels

To run the sync.Cond version:

go run ./examples/suspend/cond

🛠️ Implementation Details

Each version implements different suspension strategies:

1. sync.Cond (Legacy Style)

Uses a shared mutex and condition variable. Note that cond.Wait() cannot be easily cancelled by context, so it requires a wrapper or manual loop check.

2. Channels (v1.5+ Style)

Uses select to listen for suspend/resume signals. Fully context-aware and integrates seamlessly with lifecycle.BaseWorker.