deploy-to-kubernetes

# Deploy to Kubernetes Containerized apps → K8s. Prod-ready: health checks, resource mgmt, auto rollouts. ## Use When - New apps → K8s (EKS, GKE, AKS, self-hosted) - Compose/VMs → orchestration migrate - Zero-downtime rolling updates + rollbacks - Config + secrets mgmt - Multi-env (dev, staging, prod) - Reusable Helm charts ## In - **Required**: Cluster access (`kubectl cluster-info`) - **Required**: Images in registry (Docker Hub, ECR, GCR, Harbor) - **Required**: App reqs (ports, env vars, volumes) - **Optional**: TLS certs → HTTPS ingress - **Optional**: Persistent storage (StatefulSets, PVCs) - **Optional**: Helm CLI ## Do > See [Extended Examples](references/EXAMPLES.md) for complete configuration files and templates. ### Step 1: Namespace + resource quotas Orgs apps → namespaces w/ limits + RBAC. ```bash # Create namespace kubectl create namespace myapp-prod # Apply resource quota cat <<EOF | kubectl apply -f - apiVersion: v1 kind: ResourceQuota metadata: name: compute-quota namespace: myapp-prod spec: hard: requests.cpu: "10" requests.memory: "20Gi" limits.cpu: "20" limits.memory: "40Gi" persistentvolumeclaims: "5" services.loadbalancers: "2" --- apiVersion: v1 kind: LimitRange metadata: name: default-limits namespace: myapp-prod spec: limits: - default: cpu: "500m" memory: "512Mi" defaultRequest: cpu: "100m" memory: "128Mi" type: Container EOF # Create service account cat <<EOF | kubectl apply -f - apiVersion: v1 kind: ServiceAccount metadata: name: myapp namespace: myapp-prod --- apiVersion: rbac.authorization.k8s.io/v1 kind: Role metadata: name: myapp-role namespace: myapp-prod rules: - apiGroups: [""] resources: ["configmaps", "secrets"] verbs: ["get", "list", "watch"] --- apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: name: myapp-rolebinding namespace: myapp-prod subjects: - kind: ServiceAccount name: myapp namespace: myapp-prod roleRef: kind: Role name: myapp-role apiGroup: rbac.authorization.k8s.io EOF # Verify namespace setup kubectl get resourcequota -n myapp-prod kubectl get limitrange -n myapp-prod kubectl get sa -n myapp-prod ``` → NS created w/ quotas. LimitRange sets defaults. SA least-priv RBAC. If err: Quota → check nodes (`kubectl describe nodes`). RBAC → `kubectl auth can-i create role --namespace myapp-prod`. Rejected resources → `kubectl describe`. ### Step 2: Secrets + ConfigMaps Externalize config + sensitive data. ```bash # Create ConfigMap from literal values kubectl create configmap myapp-config \ --namespace=myapp-prod \ --from-literal=LOG_LEVEL=info \ --from-literal=API_TIMEOUT=30s \ --from-literal=FEATURE_FLAGS='{"newUI":true,"betaAPI":false}' # Create ConfigMap from file cat > app.properties <<EOF database.pool.size=20 cache.ttl=3600 retry.attempts=3 EOF kubectl create configmap myapp-properties \ --namespace=myapp-prod \ --from-file=app.properties # Create Secret for database credentials kubectl create secret generic myapp-db-secret \ --namespace=myapp-prod \ --from-literal=username=appuser \ --from-literal=password='sup3rs3cr3t!' \ --from-literal=connection-string='postgresql://db.example.com:5432/myapp' # Create TLS secret for ingress kubectl create secret tls myapp-tls \ --namespace=myapp-prod \ --cert=path/to/tls.crt \ --key=path/to/tls.key # Verify secrets/configmaps kubectl get configmap -n myapp-prod kubectl get secret -n myapp-prod kubectl describe configmap myapp-config -n myapp-prod ``` Complex → YAML: ```yaml # configmap.yaml apiVersion: v1 kind: ConfigMap metadata: name: myapp-config namespace: myapp-prod data: nginx.conf: | server { listen 8080; location / { proxy_pass http://backend:3000; proxy_set_header Host $host; } } app-config.json: | { "logLevel": "info", "features": { "authentication": true, "metrics": true } } --- # secret.yaml apiVersion: v1 kind: Secret metadata: name: myapp-secret namespace: myapp-prod type: Opaque stringData: # Automatically base64 encoded api-key: "sk-1234567890abcdef" jwt-secret: "my-jwt-signing-key" ``` → ConfigMaps → non-sensitive. Secrets → creds/keys. Pods read via env/volume. TLS → Ingress. If err: Encoding → use `stringData` not `data`. TLS → `openssl x509 -in tls.crt -text -noout`. Access → SA RBAC. Decode → `kubectl get secret myapp-secret -o jsonpath='{.data.api-key}' | base64 -d`. ### Step 3: Deployment w/ health + limits Prod-ready w/ probes + resource mgmt. ```yaml # deployment.yaml apiVersion: apps/v1 kind: Deployment metadata: name: myapp namespace: myapp-prod labels: app: myapp version: v1.0.0 spec: # no replicas: here — the HPA in Step 5 owns the count strategy: type: RollingUpdate rollingUpdate: maxSurge: 1 maxUnavailable: 0 # Zero-downtime updates selector: matchLabels: app: myapp template: metadata: labels: app: myapp version: v1.0.0 annotations: prometheus.io/scrape: "true" prometheus.io/port: "8080" prometheus.io/path: "/metrics" spec: serviceAccountName: myapp securityContext: runAsNonRoot: true runAsUser: 1000 fsGroup: 1000 containers: - name: myapp image: myregistry.io/myapp:v1.0.0 imagePullPolicy: IfNotPresent ports: - name: http containerPort: 8080 protocol: TCP env: - name: LOG_LEVEL valueFrom: configMapKeyRef: name: myapp-config key: LOG_LEVEL - name: DB_USERNAME valueFrom: secretKeyRef: name: myapp-db-secret key: username - name: DB_PASSWORD valueFrom: secretKeyRef: name: myapp-db-secret key: password - name: POD_NAME valueFrom: fieldRef: fieldPath: metadata.name - name: POD_NAMESPACE valueFrom: fieldRef: fieldPath: metadata.namespace resources: requests: cpu: 250m memory: 256Mi limits: cpu: 500m memory: 512Mi livenessProbe: httpGet: path: /healthz port: http initialDelaySeconds: 30 periodSeconds: 10 timeoutSeconds: 5 failureThreshold: 3 readinessProbe: httpGet: path: /ready port: http initialDelaySeconds: 5 periodSeconds: 5 timeoutSeconds: 3 failureThreshold: 2 startupProbe: httpGet: path: /healthz port: http initialDelaySeconds: 0 periodSeconds: 10 timeoutSeconds: 3 failureThreshold: 30 # 5 minutes for slow startup volumeMounts: - name: config mountPath: /etc/myapp readOnly: true - name: cache mountPath: /var/cache/myapp volumes: - name: config configMap: name: myapp-properties - name: cache emptyDir: {} imagePullSecrets: - name: registry-credentials ``` Apply + monitor: ```bash # Apply deployment kubectl apply -f deployment.yaml # Watch rollout status kubectl rollout status deployment/myapp -n myapp-prod # Check pod status kubectl get pods -n myapp-prod -l app=myapp # View pod logs kubectl logs -n myapp-prod -l app=myapp --tail=50 -f # Describe deployment for events kubectl describe deployment myapp -n myapp-prod # Check resource usage kubectl top pods -n myapp-prod -l app=myapp ``` → 3 replicas rolling. Readiness pre-traffic. Liveness restarts unhealthy. Limits prevent OOM. Logs show startup. If err: ImagePullBackOff → image + imagePullSecret (`kubectl get secret registry-credentials -o yaml`). CrashLoopBackOff → `kubectl logs pod-name --previous`. Probe fail → port-forward + curl. OOMKilled → increase mem or find leaks. ### Step 4: Expose via Service + LB ```yaml # service.yaml apiVersion: v1 kind: Service metadata: name: myapp namespace: myapp-prod # ... (see EXAMPLES.md for complete configuration) ``` Apply + test: ```bash # Apply services kubectl apply -f service.yaml # Get service details kubectl get svc -n myapp-prod # ... (see EXAMPLES.md for complete configuration) ``` → LB → external IP. ClusterIP → stable internal DNS. Endpoints = healthy pod IPs. Curl OK. If err: LB pending → cloud integration + quotas. No endpoints → `kubectl get pods --show-labels` matches selector. Refused → targetPort matches container. Debug → `kubectl port-forward` bypass. ### Step 5: HPA Auto scale on CPU/mem/custom. ```yaml # hpa.yaml apiVersion: autoscaling/v2 kind: HorizontalPodAutoscaler metadata: name: myapp-hpa namespace: myapp-prod # ... (see EXAMPLES.md for complete configuration) ``` Install metrics-server: ```bash # Install metrics-server kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml # Verify metrics-server kubectl get deployment metrics-server -n kube-system kubectl top nodes # ... (see EXAMPLES.md for complete configuration) ``` → HPA monitors. Scale up on threshold, down gradual. Metrics via `kubectl top`. If err: "unknown" metrics → metrics-server running + pod requests defined. No scale → `kubectl top pods` vs target. Flapping → `stabilizationWindowSeconds`. Slow → reduce `periodSeconds`. ### Step 6: Helm chart Reusable, multi-env. ```bash # Create Helm chart structure helm create myapp-chart cd myapp-chart # Edit Chart.yaml cat > Chart.yaml <<EOF # ... (see EXAMPLES.md for complete configuration) ``` → Chart packages all resources. Dry-run renders. Install orders. Upgrades roll. Rollback reverts. If err: Template → `helm template .` local render. Dep → `helm dependency update`. Values → path in values.yaml. Inspect → `helm get manifest myapp -n myapp-prod`. ## Check - [ ] Pods Running + all ready - [ ] Readiness pre-endpoints - [ ] Liveness restarts unhealthy - [ ] Reqs/limits prevent OOM + overcommit - [ ] Secrets/ConfigMaps mounted - [ ] Svcs DNS resolve (cluster.local) - [ ] LB/Ingress external - [ ] HPA scales up/down - [ ] Rolling zero-downtime - [ ] Logs → kubectl or centralized ## Traps - **No readiness**: Traffic before ready. Always readiness probes verify deps. - **Insufficient startup**: Fast liveness kills slow apps. Use startupProbe w/ high failureThreshold. - **No resource limits**: Unlimited CPU/mem → node instability. Always set reqs + limits. - **Hardcoded config**: Env-specific in manifests → no reuse. ConfigMaps, Secrets, Helm values. - **Default SA**: Unnecessary perms. Dedicated SA + minimal RBAC. - **No rolling strategy**: Recreate all → downtime. RollingUpdate + maxUnavailable: 0. - **Secrets in VCS**: Sensitive → Git. Sealed-secrets, external-secrets-operator, or vault. - **No PDB**: Cluster maint drains → break. PodDisruptionBudget → min available. ## → - `setup-docker-compose` — container fundamentals pre-K8s - `containerize-mcp-server` — images for deploy - `write-helm-chart` — advanced Helm - `manage-kubernetes-secrets` — SealedSecrets + external-secrets-operator - `configure-ingress-networking` — NGINX Ingress + cert-manager - `implement-gitops-workflow` — ArgoCD/Flux declarative - `setup-container-registry` — registry integration