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Implementing the 4th GitOps Principle in Vidra Operator

Context and Problem Statement​

The 4th GitOps principle states:
"Software agents continuously observe actual system state and attempt to apply the desired state."

During implementation, we realized that VidraResource reconciliation must also run in a loop to ensure the actual state matches the desired state.

Considered Options​

  • Time-based reconciliation loop
    Implement a simple loop that periodically checks the state of managed resources and reconciles them if they differ from the desired state. This is straightforward and ensures regular updates.

  • Event-based reconciliation
    Trigger reconciliation immediately when relevant changes are detected in managed resources. This provides a rapid response to changes but may be more resource-intensive.

Decision Outcome​

Chosen option: Both time-based and event-based reconciliation, because it combines the reliability of periodic checks with the responsiveness of event-driven updates and allows the user to configure the reconciliation interval as desired.

We first implemented a simple, time-based reconciliation loop using the reconcileAfter return value. The interval is configurable via the Vidra ConfigMap, allowing operators to tune how often reconciliation occurs.

We then added event-based reconciliation, which triggers reconciliation immediately when relevant changes are detected in managed resources. This enables faster reactions to changes but may be more resource-intensive.

Consequences​

  • Good, because it combines reliability (periodic checks) with responsiveness (event-driven updates).
  • Good, because it allows operators to configure the reconciliation interval based on their specific needs and resource constraints.
  • Bad, because event-based reconciliation can be more resource-intensive, so careful configuration and monitoring are required.
  • Bad, because implementing both mechanisms increases complexity, requiring careful management of reconciliation logic to avoid conflicts or redundant operations/reconciliation loops.