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Snapshot Apply

We need a repeatable process that can take current database and system states, use those to create a plan of action, then apply that plan to the current cluster.

The snapshot apply process in the control-server binary is that system. It consists of five steps:

  1. Prepare: Take a point-in-time snapshot of everything.
  2. Generate: Feed that snapshot into functional code that generate the desired system states.
  3. Apply: Apply any changes needed to go from the current state to the desired state on all systems.
  4. Record: Record the status for all desired state pieces.
  5. Broadcast: Broadcast the result of the overall attempt.

Prepare

The preparation phase involves creating a comprehensive snapshot of the current system:

  • Use the system state summarizer to compile a detailed summary of all database contents and the current system state.
  • Generate target snapshots for different systems (KubeSnapshot and KeyCloakSnapshot).

Generate

In the generation phase, we transform the snapshot into actionable plans:

  • For each target snapshot, use the summarized system state with functional modules to generate target system specifications.
  • Store each Kubernetes or Keycloak target resource in the database (ResourcePath for Kubernetes).

Apply

The application phase is where changes are implemented:

  • Compare target system configurations with existing resources, removing any that already match. For Kubernetes, this involves using sha hmac via KubeExt.Hashing.
  • Update any matching resources that are successfully applied.
  • Push each of the Kubernetes resource targets to kubernetes using KubeExt.ApplyResource.
  • Push each of the Keycloak resource targets to Keycloak
  • Trigger any necessary post-apply operations for Keycloak.

Record

Accurate record-keeping improves system integrity, providing historical context and features like rollbacks:

  • Record the results for each individual resource target.
  • Compute an overall result of the operation.

Broadcast

Finally, we ensure all relevant parties are informed:

  • Transmit the latest result via Phoenix pub sub and EventCenter.

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