Composition Dynamic Controller

The composition-dynamic-controller is an operator that is instantiated by the core-provider to manage the Custom Resources whose Custom Resource Definition is generated by the core-provider.

Summary

• Summary
• Architecture
• Overview
• Examples
• Configuration

Architecture

Workflow

Composition Dynamic Controller (CDC) & Chart Inspector: Secure Helm Lifecycle Management

The Composition Dynamic Controller (CDC) is a specialized Kubernetes operator that orchestrates the end-to-end lifecycle of Krateo compositions. Acting as the reconciliation engine for Composition custom resources, it bridges declarative application definitions with Helm’s packaging system through intelligent automation. The Chart Inspector serves as its "safety advisor," enabling proactive decision-making via dry-run analysis.

Core CDC Workflow (with Chart Inspector Integration)

1. Reconciliation Trigger

   • Watches for changes to Composition CRs or Helm chart versions.
   • Invokes the Chart Inspector to simulate installations/upgrades before execution.

2. Dry-Run Analysis Phase (Chart Inspector)

   helm install --dry-run=server <chart> --version <ver>  # Returns:

   • Resource Manifest List: All Kubernetes objects (Deployments, CRDs, etc.) the chart would create along with filename to .
   • Dependency Graph: Order of operations (e.g., CRDs before custom resources).

3. RBAC Auto-Provisioning (CDC)

   • Dynamically generates least-privilege Roles/ClusterRoles based on the Inspector’s output.
   • Ensures the CDC’s service account has exactly the permissions needed—no more, no less.

4. Atomic Execution (CDC)

   • Proceeds with helm install/upgrade only after successful dry-run and RBAC setup.

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Key Capabilities Enabled by This Collaboration

Feature	CDC’s Role	Chart Inspector’s Contribution
Version-Sensitive Reconciliation	Detects chart version drift; rolls forward/back.	Identifies version-specific resource changes during dry-run.
Atomic Upgrades	Ensures all-or-nothing upgrades.	Pre-flights resource compatibility (e.g., CRD schema changes).
Self-Healing	Corrects configuration drift.	Provides baseline "desired state" for comparison.
Declarative Enforcement	Continuously reconciles actual vs. desired state.	Supplies the desired state before cluster changes.
Secure RBAC	Generates minimal required permissions.	Audits chart manifests for required API operations.

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Why This Architecture Matters

1. Safety Net

   • The Chart Inspector’s dry-run prevents "helm surprises" (e.g., undeclared CRD creations or namespace pollution).
   • Example: Blocks a chart upgrade if the new version requires a ClusterRole the CDC isn’t authorized to manage.

2. GitOps Compliance

   • The CDC enforces declarative intent by reconciling against the dry-run’s output, not just Helm’s last-applied state.
   • Self-healing kicks in if manual changes violate the composition’s definition.

3. Multi-Tenancy Ready

   • RBAC is scoped per-composition, isolating teams/projects.
   • The Inspector’s resource listing ensures no cross-tenant leakage (e.g., a composition can’t create resources in forbidden namespaces).

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Real-World Example: Handling a Breaking Chart Change

1. Scenario: A Helm chart v1.2.0 introduces a new CustomResourceDefinition (CRD).
2. CDC+Inspector Flow:
   • Dry-run detects the new CRD and its required API group permissions.
   • CDC creates a ClusterRole granting create/get/list for the CRD.
   • Upgrade proceeds only after the CRD and RBAC are confirmed active.
3. Result: Zero downtime; no "helm upgrade failed: CRD missing" errors.

Configuration

Operator Env Vars

These enviroment varibles can be changed in the Deployment of the composition-dynamic-controller we need to tweak.

Name	Description	Default Value	Notes
COMPOSITION_CONTROLLER_DEBUG	dump verbose output	false
COMPOSITION_CONTROLLER_WORKERS	number of workers	1
COMPOSITION_CONTROLLER_RESYNC_INTERVAL	resync interval	3m
COMPOSITION_CONTROLLER_GROUP	resource api group		populated by core-provider
COMPOSITION_CONTROLLER_VERSION	resource api version		populated by core-provider
COMPOSITION_CONTROLLER_RESOURCE	resource plural name		populated by core-provider
COMPOSITION_CONTROLLER_SA_NAME	cdc deployment ServiceAccount name		populated by core-provider
COMPOSITION_CONTROLLER_SA_NAMESPACE	cdc deployment ServiceAccount namespace	populated by core-provider
URL_PLURALS	url to krateo pluraliser service	http://snowplow.krateo-system.svc.cluster.local:8081/api-info/names
URL_CHART_INSPECTOR	url to chart inspector	http://chart-inspector.krateo-system.svc.cluster.local:8081/
KRATEO_NAMESPACE	namespace where krateo is installed	krateo-system
HELM_REGISTRY_CONFIG_PATH	default helm config path	/tmp
HELM_MAX_HISTORY	Max Helm History	10
COMPOSITION_MAX_ERROR_RETRY_INTERVAL	The maximum interval between retries when an error occurs. This should be less than the half of the poll interval.	0m
COMPOSITION_MIN_ERROR_RETRY_INTERVAL	The minimum interval between retries when an error occurs. This should be less than max-error-retry-interval.	1m