Controller Design

Design and implementation of the Bindy controller.

Controller Pattern

Bindy implements the Kubernetes controller pattern:

1. Watch - Monitor CRD resources
2. Reconcile - Ensure actual state matches desired
3. Update - Apply changes to Kubernetes resources

Reconciliation Loop

#![allow(unused)]
fn main() {
loop {
    // Get resource from work queue
    let resource = queue.pop();
    
    // Reconcile
    match reconcile(resource).await {
        Ok(_) => {
            // Success - requeue with normal delay
            queue.requeue(resource, Duration::from_secs(300));
        }
        Err(e) => {
            // Error - retry with backoff
            queue.requeue_with_backoff(resource, e);
        }
    }
}
}

State Management

Controller maintains no local state - all state in Kubernetes:

• CRD resources (desired state)
• Deployments, Services, ConfigMaps (actual state)
• Status fields (observed state)

Error Handling

• Transient errors: Retry with exponential backoff
• Permanent errors: Update status, log, requeue
• Resource conflicts: Retry with latest version