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Kubernetes Operator with controller-runtime: Status, Finalizers, Webhooks, and Drift
Part 2 of 3: extend a DemoApp Operator SDK project with ConfigMap, Service, Deployment, status Conditions, finalizers, drift via Owns/Watches, mutating/validating webhooks, Events, and RBAC markers.
Go Kubernetes Operator SDK Tutorial: Build a Controller from Scratch
Part 1 of 3: scaffold a Go operator with Operator SDK (go/v4), CRDs from Kubebuilder markers, RBAC, idempotent Reconcile with CreateOrUpdate, owner references, and deploy to kind.
Server-Side Apply (SSA) in Kubernetes Operators
Server-Side Apply (SSA) is the modern way for operators to express ownership of fields in a Kubernetes object. Instead of doing a full Update with a stale copy of the object, the operator sends only the fields it cares …
Multi-Tenant Kubernetes Operator Patterns: Per-Namespace Leases and Listers
Multi-tenant operators come in three shapes: one operator serving all tenants (shared, simple, weakest isolation), one operator per tenant (isolated, expensive, strongest isolation), and the hybrid — one operator binary …
Operator Leader Election Explained: HA Operators with Lease Locks
A complete guide to running a multi-replica Kubernetes operator with leader election: how the lease-based lock works, the four manager options (`LeaderElection`, `LeaderElectionID`, `LeaderElectionResourceLock`, …
Operator Health and Readiness Probes: /healthz, /readyz, AddHealthzCheck
A practical guide to liveness and readiness probes for Kubernetes operators: what `/healthz` and `/readyz` should report, how to register custom checks with `mgr.AddHealthzCheck` and `mgr.AddReadyzCheck`, the difference …
Kubernetes Operator Watches, Events, and Predicates Explained
Learn how Kubernetes Operator watches, events, handlers, and predicates decide which changes trigger Reconcile, with Owns vs Watches examples.
Multi-Resource Reconciliation: Managing N Child Resources per CR
Most real operators do not manage one child — they manage five, ten, sometimes dozens of children per CR: a Deployment, a Service, two ConfigMaps, a HorizontalPodAutoscaler, a NetworkPolicy, a ServiceAccount, a …
Kubernetes Status Subresource and Conditions Explained (KEP-1623)
The status subresource is the API server endpoint controllers use to publish observed state without racing user edits on `.spec`. This guide explains why the split exists, the KEP-1623 Conditions standard (Ready / …
The Kubernetes Reconcile Loop Explained: From API Event to Reconcile()
Learn how the Kubernetes reconcile loop works from API watch to informer cache, workqueue, and Reconcile(). Covers level-triggered control, Result return paths, requeue behavior, idempotency, concurrency, and hot loop …
Kubernetes Operator Capability Levels I–V: The Operator Maturity Model
Red Hat's five operator capability levels - Basic Install, Seamless Upgrades, Full Lifecycle, Deep Insights, Auto Pilot - are the maturity scale used by OperatorHub and OLM. This guide explains what each level means, …
Kubernetes Operator Design Patterns: Singleton, Capability, Lifecycle, Auto-Pilot
Kubernetes Operators are not one shape - six distinct design patterns cover the entire range of production deployments: Singleton, Capability, Lifecycle, Auto-Pilot / Auto-Tune, Sidecar-Injecting, and GitOps-Controlled. …
Mutating and Validating Admission Webhooks in Operators
A complete guide to admission webhooks for Kubernetes operators: the difference between mutating and validating, the webhook lifecycle inside the API server, how kubebuilder scaffolds …
Kubernetes Finalizers: Two-Phase Deletion, Cleanup Patterns, and Stuck Objects
A Kubernetes finalizer is a string on `metadata.finalizers` that tells the API server to keep an object alive (with `deletionTimestamp` set) until your controller has finished cleanup and removed the string. This …
Helm-Based Operator vs Flux vs Argo CD: Which to Use
Three tools install Helm charts on a Kubernetes cluster: a Helm-based operator (per-CR Helm install), Flux's HelmRelease (HelmRelease CR + per-source reconciler), and Argo CD's Application (Application CR + sync engine). …
Drift Detection Patterns in Kubernetes Operators: Periodic Resync vs Spec Diffing
A Kubernetes operator detects drift in four layered ways: watch-based reconciliation, periodic resync with SyncPeriod, three-way spec diffing with client.Patch or Server-Side Apply, and external polling for resources …
Desired State vs Actual State in Kubernetes: The Level-Triggered Model
In Kubernetes, the desired state is what you declared in `.spec`, the actual state is what currently exists in the cluster, and the controller's job is to continuously reconcile the two. This guide explains why …
Helm Hybrid Operator Tutorial Part 1 of 2 - Build the Foundation (Go + Helm v4 SDK)
A Helm hybrid operator is a Go operator whose Reconcile calls the Helm SDK (v4) directly - the pre-built helm-operator, written by you, with full control. Part 1 of 2 walks the foundation: scaffold with operator-sdk init …
Helm Hybrid Operator Tutorial Part 2 of 2 - Custom Status, Finalizer, Drift, Cross-CR
Part 2 of the Helm hybrid operator tutorial: the features the pre-built helm-operator binary cannot provide, written in roughly 200 lines of Go on top of the foundation built in Part 1. Custom status fields including a …
Helm-Based Operator Tutorial Part 1 - Build the Operator (Chart, CRD, watches.yaml)
A Helm-based operator wraps a Helm chart as a Kubernetes operator without you writing any Go code. The Operator SDK ships a generic reconciler that watches a CR, maps its `.spec` to Helm values, and runs `helm install` / …
Owner References and Garbage Collection in Kubernetes Operators
A complete guide to owner references and Kubernetes garbage collection for operators: the contract between an owner and its dependents, the difference between `SetControllerReference` and `SetOwnerReference`, three …
Install Operator-SDK on Linux: Complete Setup Guide (Go, kubectl, Helm 4, kind, ttl.sh registry)
A complete step-by-step guide to installing Operator-SDK on Linux (Ubuntu, RHEL, Fedora, Debian), including the prerequisite toolchain (Go 1.22+, kubectl, container runtime, Helm 4 CLI, kind), the three Operator-SDK …
Kubernetes Operator vs Controller vs CRD: What's the Difference?
A Custom Resource Definition (CRD) is the API contract, a Controller is the reconciler that watches and acts on it, and an Operator is the combination of a CRD plus a controller plus domain-specific knowledge about a …
What is a Kubernetes Operator?
A Kubernetes Operator is a custom controller paired with a Custom Resource Definition (CRD) that automates the day-2 operations of a complex application - install, upgrade, backup, failover, scaling - by continuously …
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