Kubernetes

Name: kubernetes
Rating: 88
Author: Tyler-R-Kendrick

Overview

Kubernetes orchestrates containerized applications across clusters of machines, handling deployment, scaling, networking, and self-healing. Resources are declared in YAML manifests and managed via kubectl or GitOps tools.

Deployment

yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
  labels:
    app: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: app
          image: my-app:1.0.0
          ports:
            - containerPort: 8080
          resources:
            requests:
              cpu: 100m
              memory: 128Mi
            limits:
              cpu: 500m
              memory: 256Mi
          livenessProbe:
            httpGet:
              path: /healthz
              port: 8080
            initialDelaySeconds: 10
            periodSeconds: 15
          readinessProbe:
            httpGet:
              path: /ready
              port: 8080
            initialDelaySeconds: 5
            periodSeconds: 5
          env:
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: db-credentials
                  key: url

Service

yaml

apiVersion: v1
kind: Service
metadata:
  name: my-app
spec:
  selector:
    app: my-app
  ports:
    - port: 80
      targetPort: 8080
  type: ClusterIP

Ingress

yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt-prod
spec:
  tls:
    - hosts: [my-app.example.com]
      secretName: my-app-tls
  rules:
    - host: my-app.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: my-app
                port:
                  number: 80

ConfigMap and Secret

yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  LOG_LEVEL: "info"
  FEATURE_FLAGS: "new-ui=true"
---
apiVersion: v1
kind: Secret
metadata:
  name: db-credentials
type: Opaque
stringData:
  url: "postgresql://user:pass@db:5432/myapp"

Key Commands

bash

# Apply manifests
kubectl apply -f manifests/

# Check rollout status
kubectl rollout status deployment/my-app

# Scale
kubectl scale deployment/my-app --replicas=5

# View logs
kubectl logs -f deployment/my-app

# Port forward for debugging
kubectl port-forward svc/my-app 8080:80

# Diff before apply
kubectl diff -f manifests/

Best Practices

•Always set resource requests and limits to ensure fair scheduling and prevent noisy neighbors.
•Use liveness probes (restart on failure) and readiness probes (stop routing traffic) for self-healing.
•Use Secrets for sensitive data, ConfigMaps for configuration — never hardcode either.
•Use kubectl diff before kubectl apply to review changes.
•Pin container image tags to specific versions (not latest) for reproducible deployments.
•Use namespaces to isolate environments or teams.
•Use labels and selectors consistently for organizing and querying resources.
•Use rolling update strategy (default) with maxUnavailable and maxSurge for zero-downtime deploys.