MetalLB is a Kubernetes-native load balancer for bare-metal clusters. Two cooperating workloads implement the system: a cluster-scoped controller that allocates IP addresses from CRD-defined IPAddressPools and writes Service status updates, and a DaemonSet of speaker pods on each node that announce assigned IPs to the physical network. Announcement is either BGP (via a from-scratch native Go BGP stack, a deprecated FRR sidecar mode, or the newer FRR-K8s API that generates FRRConfiguration CRs) or Layer2 (ARP/NDP responders with memberlist-based fast failover detection and deterministic speaker election). All user configuration flows through CRDs — IPAddressPool, BGPPeer, BGPAdvertisement, L2Advertisement, Community, BFDProfile, and ConfigurationState — validated by admission webhooks, with a configmaptocrs tool migrating legacy ConfigMap configuration to the CRD model. The controller/speaker split, a listener abstraction that delivers config changes to protocol handlers, and a common bgp.Session interface across backends give the architecture a clean, modular shape.
Bitnami Sealed Secrets is a Kubernetes controller and CLI tool that enables secure storage of encrypted Kubernetes Secrets in version control. The system consists of a cluster-side operator and a client-side CLI (`kubeseal`). The controller watches for custom `SealedSecret` custom resource definitions (CRDs) and decrypts them into regular Kubernetes `Secret` objects using asymmetric encryption (RSA-OAEP for key encapsulation and AES-256-GCM for data encryption). The CLI allows users to encrypt secrets using the controller's public certificate, validate sealed secrets, and re-encrypt them under different keys. The controller is deployed via a Helm chart or raw manifests, exposes Prometheus metrics, and provides HTTP endpoints for certificate retrieval, verification, and key rotation. The codebase is mature, well-tested with both unit and integration tests, and follows standard Kubernetes operator patterns (informers, work queues, status updates). It has a low technical drift, with recent dependency updates and active maintenance.
This is a Kubernetes controller that manages Helm chart deployments via Custom Resource Definitions (HelmChart and HelmChartConfig). It watches these CRDs and creates Kubernetes Jobs to run Helm install, upgrade, or delete operations, with a two-phase apply pattern that suspends jobs before updating them to avoid race conditions. The controller is built on the rancher/wrangler framework and handles complex features like failure policies, server-side apply, driver selection (secret vs configmap), values from secrets, HelmChartConfig merging, and bootstrapping. It is the core Helm management component of k3s and is designed to be deployed as a Deployment with a ServiceAccount and ClusterRole.
This repository implements a Kubernetes Operator for managing MongoDB Atlas resources. It provides Custom Resource Definitions (CRDs) and controllers that reconcile user-defined specifications (projects, clusters, database users, network peering, backup schedules, private endpoints, search indexes, stream instances, federated authentication, etc.) against the MongoDB Atlas API. The operator supports both API key and OAuth (service account) authentication, multiple deployment modes (cluster-wide, namespaced, OpenShift), and features like dry-run validation, deletion protection, and independent sync periods for cross-project resources. Architecturally, the operator follows the standard kubebuilder/controller-runtime pattern with a manager that registers multiple reconcilers. It has a hand-written core for legacy CRDs (e.g., AtlasProject, AtlasDeployment) and a generated state-machine-based controller layer for newer CRDs (Group, Cluster, FlexCluster, DatabaseUser, IPAccessListEntry) using the crd2go/constate library. A translation layer converts between CRD specs and Atlas SDK DTOs, and indexers enable cross-resource watch triggers. Extensive unit, integration, and end-to-end tests (Ginkgo/Gomega) validate behavior against real Atlas environments. The codebase is professional-grade with clear separation of concerns, reusable utility packages (comparison, time, pointer, HTTP diff client, JSON slice merge for version compatibility), and mature CI/CD pipelines including Helm charts, OLM bundles, SBOM generation, and Red Hat certification scripts. While it is tightly coupled to MongoDB Atlas and not directly reusable as a library, the operator patterns—especially the dry-run transport, state-machine delegation, and version-compatible JSON merging—demonstrate non-obvious engineering skill applicable to other Kubernetes operators.