Reconcile

Reconciliation is the core control loop pattern in Kubernetes: compare desired state (manifest spec) against actual state (cluster reality) and take actions to make them match.

Level-triggered vs edge-triggered

Reconciliation is level-triggered: it reacts to the current state, not just the event that triggered it. This means:

• Missed events don't cause permanent inconsistency — the next reconcile corrects it
• The function must be idempotent: running it multiple times produces the same result
• On failure, simply requeue — no need to track what partially happened

This is more resilient than imperative, edge-triggered approaches.

Key properties

• Idempotent — safe to run repeatedly
• Self-healing — drift from desired state is corrected automatically
• Eventually consistent — the system converges, not necessarily immediately
• Optimistic — assumes things usually work; retries on failure