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.

Composition Dynamic Controller Values Injection

The composition-dynamic-controller inject labels and values into the installed resources and in the helm chart release values. This values contains informations about the composition resource associated with the helm release. The values are injected in the following way:

Helm Chart Release Values	Installed Resources Labels	Description
global.compositionId	krateo.io/composition-id	The composition resource uid
global.compositionName	krateo.io/composition-name	The composition resource name
global.compositionNamespace	krateo.io/composition-namespace	The composition resource namespace
global.compositionInstalledVersion	krateo.io/composition-installed-version	The version of the composition resource installed. This value changes if the chart version is upgraded
global.compositionApiVersion	not injected	The api version of the composition resource. This values is deprecated but is mainteined for backward compatibility.
global.compositionGroup	krateo.io/composition-group	The group of the composition resource.
global.compositionResource	krateo.io/composition-resource	The plural name of the composition resource.
global.compositionKind	krateo.io/composition-kind	The kind of the composition resource.
global.krateoNamespace	krateo.io/krateo-namespace	The namespace where Krateo is installed. This value is used to identify the Krateo resources in the cluster.
global.gracefullyPaused	not injected	This value is set to true if the annotation krateo.io/gracefully-paused is set on the composition resource. This value is used to pause the reconciliation of the composition resource only after the value is injected in the helm release values with a successful helm upgrade. Read the paragraph below for more details.

About the gracefullyPaused value

The global.gracefullyPaused value provides a way to gracefully pause both the composition resource and all Krateo resources within its Helm chart.

How it works:

1. Trigger: Set the annotation krateo.io/gracefully-paused on the composition resource
2. Activation: The pause takes effect only after the next successful Helm upgrade injects this value into the chart
3. Scope: Pauses both the composition reconciliation AND any Krateo resources in the chart that respect the krateo.io/paused annotation

Use cases:

• Graceful pause: Temporarily halt all composition-related activity without resource deletion
• Coordinated pause: Ensure both the composition and its managed resources pause simultaneously
• Safe maintenance: Pause operations during maintenance windows

Comparison with krateo.io/paused:

Annotation	Scope	When it takes effect
krateo.io/gracefully-paused	Composition + chart resources	After next Helm upgrade
krateo.io/paused	Composition only	Immediately

Example: Use krateo.io/gracefully-paused when you need to pause an entire application stack, or krateo.io/paused for immediate composition-only pausing.

How to include the pause in a resource included in the chart

To include the pause in a resource included in the chart, you can use the krateo.io/paused annotation on the resource. This will ensure that the resource is paused when the composition is paused.

apiVersion: git.krateo.io/v1alpha1
kind: Repo
metadata:
  name: {{ include "fireworks-app.fullname" . }}-repo
  labels:
    {{- include "fireworks-app.labels" . | nindent 4 }}
  annotations:
    krateo.io/paused: "{{ default false (and .Values.global .Values.global.gracefullyPaused) }}"
spec:
...

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	NOT USED from version 0.17.1 - URL to krateo pluraliser service	http://snowplow.krateo-system.svc.cluster.local:8081/api-info/names	Ignored from version 0.17.1
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_CONTROLLER_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_CONTROLLER_MIN_ERROR_RETRY_INTERVAL	The minimum interval between retries when an error occurs. This should be less than max-error-retry-interval.	1m
COMPOSITION_CONTROLLER_METRICS_SERVER_PORT	The port where the metrics server will be listening. If not set, the metrics server is disabled.