January 13, 2025 5 min to read

Kubernetes Deployment Strategies

• image reference link

Overview

Kubernetes deployment strategies define how to update Pods or sets of Pods when deploying new application versions or container images.

• RollingUpdate is the default strategy.
• Recreate is the strategy that terminates all existing pods before creating new ones.

🔄 Basic Deployment Strategies

1. RollingUpdate (Default)

spec:
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1  # Maximum number of pods that can be unavailable during update
      maxSurge: 1       # Maximum number of pods that can be created above desired number

• Gradually updates pods in small batches
• Minimizes downtime during updates
• Ideal for maintaining high availability
• Controls update pace with maxUnavailable and maxSurge parameters

2. Recreate

spec:
  strategy:
    type: Recreate

• Terminates all existing pods before creating new ones
• Results in downtime between versions
• Ensures clean deployment of new version
• Suitable for development environments or when downtime is acceptable

Strategy Comparison Table

Advanced Deployment Strategies

1. Blue/Green Deployment

• Maintains two identical environments (blue and green)
• Switches traffic instantly between versions
• Provides zero downtime deployment
• Enables immediate rollback capability
• Requires double the resources

# Blue/Green Deployment Service
apiVersion: v1
kind: Service
metadata:
  name: my-app
spec:
  selector:
    app: my-app
    version: blue  # Switch between blue and green
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080

2. Canary Deployment

• Gradually rolls out changes to a subset of users
• Enables risk mitigation through partial deployment
• Allows testing with real user traffic
• Requires sophisticated traffic control

# Canary Deployment with Ingress
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    nginx.ingress.kubernetes.io/canary: "true"
    nginx.ingress.kubernetes.io/canary-weight: "20"

Strategy Selection Guide

🔍 Deployment Health Checks

1. Readiness Probe

spec:
  containers:
  - name: my-app
    readinessProbe:
      httpGet:
        path: /health
        port: 8080
      initialDelaySeconds: 5
      periodSeconds: 10

• Determines when a pod is ready to accept traffic
• Essential for smooth rolling updates
• Prevents routing to partially started pods

2. Liveness Probe

spec:
  containers:
  - name: my-app
    livenessProbe:
      httpGet:
        path: /health
        port: 8080
      initialDelaySeconds: 15
      periodSeconds: 20

• Checks if a pod is healthy and running
• Automatically restarts unhealthy pods
• Crucial for maintaining application reliability

Advanced Configuration Options

1. Progressive Delivery with Argo Rollouts

apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: my-app-rollout
spec:
  strategy:
    canary:
      steps:
      - setWeight: 20
      - pause: {duration: 1h}
      - setWeight: 40
      - pause: {duration: 1h}

• Automated canary analysis
• Traffic weight management
• Metric-based promotion/rollback

2. A/B Testing Configuration

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    nginx.ingress.kubernetes.io/canary: "true"
    nginx.ingress.kubernetes.io/canary-by-header: "User-Country"
    nginx.ingress.kubernetes.io/canary-by-header-value: "US"

• Feature testing with specific user segments
• Header-based routing
• Geographical distribution

Common Pitfalls and Best Practices

Monitoring Deployments

Key Metrics to Monitor

• Deployment success rate
• Rollout duration
• Error rates during deployment
• Resource utilization
• Response times
• Pod health status

Example Prometheus Query

rate(http_requests_total{status!~"5.."}[5m]) 
/ 
rate(http_requests_total[5m])

📚 Reference

• Kubernetes Official Documentation
• Spacelift Deployment Strategies
• DevOps Engineer Wiki