# Crossplane — The Cloud Native Control Plane Framework

> Crossplane extends Kubernetes with Custom Resources that represent cloud infrastructure, letting you compose and manage AWS, Azure, GCP, and SaaS resources with kubectl and GitOps.

## Install

Save as a script file and run:

# Crossplane — The Cloud Native Control Plane Framework

## Quick Use
```bash
# Install Crossplane into a cluster
helm repo add crossplane-stable https://charts.crossplane.io/stable
helm install crossplane crossplane-stable/crossplane 
  -n crossplane-system --create-namespace

# Install a provider (AWS)
kubectl apply -f - <<YAML
apiVersion: pkg.crossplane.io/v1
kind: Provider
metadata: {name: provider-aws}
spec:
  package: xpkg.upbound.io/crossplane-contrib/provider-aws:v0.48.1
YAML

# Claim a managed resource declaratively
kubectl apply -f - <<YAML
apiVersion: s3.aws.crossplane.io/v1beta1
kind: Bucket
metadata: {name: demo-bucket-$(date +%s)}
spec:
  forProvider: {locationConstraint: us-east-1}
  providerConfigRef: {name: default}
YAML
```

## Introduction
Crossplane turns Kubernetes into a universal control plane. Instead of running Terraform on a schedule, you install a provider package for AWS, GCP, Azure, Kubernetes, GitHub, Grafana, or dozens of SaaS products and then create infrastructure using normal Kubernetes resources. A controller continuously reconciles actual cloud state with the declared spec — just like workloads.

## What Crossplane Does
- Extends the Kubernetes API with Managed Resources representing external cloud objects.
- Composes higher-level APIs (e.g. `XPostgres`) from many Managed Resources via `CompositeResourceDefinitions`.
- Reconciles infrastructure continuously — drift is corrected, not just detected.
- Ships an official package manager (`Provider`, `Function`, `Configuration`) with signed OCI artifacts.
- Works hand-in-hand with Argo CD or Flux for full GitOps infra delivery.

## Architecture Overview
Crossplane runs as a core controller plus one controller per installed Provider. Managed Resources are CRDs generated from each Provider''s API surface (e.g. `RDSInstance.rds.aws.crossplane.io`). A Composition maps a Composite Resource Claim to one or more Managed Resources via patches and transforms. Composition Functions (v1.14+) let you write composition logic in Go, KCL, or WASM instead of YAML patches.

## Self-Hosting & Configuration
- Install with the Helm chart; no external database is required — state lives in Kubernetes.
- Store cloud credentials as Kubernetes `Secret`s referenced by `ProviderConfig` objects.
- Use multiple `ProviderConfig`s for multi-account or multi-region layouts.
- Package your platform APIs as `Configuration` OCI images and push to any OCI registry.
- Observe controllers via Prometheus — reconciliation time, error count, and drift events are first-class metrics.

## Key Features
- Treats infrastructure as Kubernetes resources — the same RBAC, admission, and audit trail as Pods.
- 100+ official and community providers: AWS, GCP, Azure, Alibaba, IBM, Equinix, Kafka, Vault, Datadog, …
- Composition Functions with Go / KCL / Starlark / WASM for flexible platform APIs.
- Vendor-neutral — swap out a provider without rewriting user-facing Claims.
- CNCF Incubating, strong commercial backing by Upbound and community maintainers.

## Comparison with Similar Tools
- **Terraform** — imperative plans + state files; Crossplane is continuous, native Kubernetes reconciliation.
- **Pulumi** — general-purpose IaC in real languages; Crossplane focuses on K8s-native self-service platforms.
- **AWS Controllers for Kubernetes (ACK)** — AWS-only; Crossplane covers many clouds and adds Composition.
- **Config Connector** — Google-specific; Crossplane generalizes the pattern across providers.
- **ArgoCD Application Sets + Terraform** — still works, but lacks live drift correction and composite APIs.

## FAQ
**Q: Does Crossplane replace Terraform?**
A: It can, and also complements it — many teams keep Terraform for day-zero infra and use Crossplane for app-team self-service.

**Q: Where is the state stored?**
A: In Kubernetes — Managed Resource `.status` fields hold external identifiers; no separate state file.

**Q: Can I import existing cloud resources?**
A: Yes — set `metadata.annotations.crossplane.io/external-name` to the resource ID and Crossplane will adopt it.

**Q: How do I write a custom composition?**
A: Author a `CompositeResourceDefinition` plus a `Composition`, or use a Composition Function for code-driven logic.

## Sources
- https://github.com/crossplane/crossplane
- https://docs.crossplane.io


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Source: https://tokrepo.com/en/workflows/22cb64cd-38cf-11f1-9bc6-00163e2b0d79
Author: Script Depot