Blue-Green & Deployment Strategies

---
name: blue-green-deploy
description: Configure zero-downtime deployment strategies including blue-green, canary,
  and rolling deployments.
category: devops
risk: critical
source: https://github.com/BagelHole/DevOps-Security-Agent-Skills
source_repo: BagelHole/DevOps-Security-Agent-Skills
source_type: community
date_added: '2026-09-20'
license: MIT
license_source: https://github.com/BagelHole/DevOps-Security-Agent-Skills/blob/main/LICENSE
compatibility: Requires the relevant platform CLIs (kubectl, helm, terraform, git,
  CI runners) and authorized access to the target environment. Docs-only; helper scripts
  and templates not bundled.
metadata:
  author: devops-skills
  version: '1.0'
---

# Blue-Green & Deployment Strategies

Implement zero-downtime deployment patterns for production systems.

## Prerequisites

- Load balancer or ingress controller
- Container orchestration (K8s) or cloud platform
- CI/CD pipeline
- Health check endpoints

## Deployment Strategy Overview

```
┌─────────────────────────────────────────────────────────────┐
│                    DEPLOYMENT STRATEGIES                     │
├─────────────┬─────────────┬─────────────┬──────────────────┤
│  Blue-Green │   Canary    │   Rolling   │    Recreate      │
├─────────────┼─────────────┼─────────────┼──────────────────┤
│ Full env    │ Gradual %   │ Pod by pod  │ All at once      │
│ swap        │ rollout     │ replacement │                  │
├─────────────┼─────────────┼─────────────┼──────────────────┤
│ Instant     │ Slow, safe  │ Moderate    │ Fast, risky      │
│ rollback    │ rollback    │ rollback    │                  │
├─────────────┼─────────────┼─────────────┼──────────────────┤
│ 2x resources│ +10-25%     │ Same        │ Same             │
│ needed      │ resources   │ resources   │                  │
└─────────────┴─────────────┴─────────────┴──────────────────┘
```

## Blue-Green Deployment

### Concept

```
Before:
┌─────────┐     ┌───────────────┐
│  Users  │────▶│  Blue (v1)    │ ◀── Active
└─────────┘     └───────────────┘
                ┌───────────────┐
                │  Green (v2)   │ ◀── Staging
                └───────────────┘

After Switch:
┌─────────┐     ┌───────────────┐
│  Users  │     │  Blue (v1)    │ ◀── Standby
└─────────┘     └───────────────┘
      │         ┌───────────────┐
      └────────▶│  Green (v2)   │ ◀── Active
                └───────────────┘
```

### Kubernetes Implementation

```yaml
# blue-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-blue
  labels:
    app: myapp
    version: blue
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
      version: blue
  template:
    metadata:
      labels:
        app: myapp
        version: blue
    spec:
      containers:
      - name: myapp
        image: myapp:v1.0.0
        ports:
        - containerPort: 8080
        readinessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5
---
# green-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-green
  labels:
    app: myapp
    version: green
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
      version: green
  template:
    metadata:
      labels:
        app: myapp
        version: green
    spec:
      containers:
      - name: myapp
        image: myapp:v2.0.0
        ports:
        - containerPort: 8080
        readinessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5
---
# service.yaml - Switch by changing selector
apiVersion: v1
kind: Service
metadata:
  name: myapp
spec:
  selector:
    app: myapp
    version: blue  # Change to 'green' to switch
  ports:
  - port: 80
    targetPort: 8080
```

### Switch Script

```bash
#!/bin/bash
# blue-green-switch.sh

set -euo pipefail
NEW_VERSION=${1:?Usage: blue-green-switch.sh blue|green}
case "$NEW_VERSION" in blue|green) ;; *) echo "Invalid color" >&2; exit 2 ;; esac

CURRENT=$(kubectl get svc myapp -o jsonpath='{.spec.selector.version}')

echo "Current version: $CURRENT"
echo "Switching to: $NEW_VERSION"

# Verify new deployment is ready
kubectl rollout status "deployment/myapp-$NEW_VERSION" --timeout=300s

# Check health
HEALTH=$(kubectl exec "deployment/myapp-$NEW_VERSION" -- curl --fail --silent --show-error --max-time 5 localhost:8080/ready)
if ! printf '%s' "$HEALTH" | jq -e '.status == "healthy"' >/dev/null; then
  echo "Health check failed"
  exit 1
fi

# Switch traffic
kubectl patch svc myapp -p "{\"spec\":{\"selector\":{\"version\":\"$NEW_VERSION\"}}}"

echo "Switched to $NEW_VERSION"
```

### AWS ECS Blue-Green

```yaml
# AWS CodeDeploy appspec.yml
version: 0.0
Resources:
  - TargetService:
      Type: AWS::ECS::Service
      Properties:
        TaskDefinition: "arn:aws:ecs:region:account:task-definition/myapp:2"
        LoadBalancerInfo:
          ContainerName: "myapp"
          ContainerPort: 8080
Hooks:
  - BeforeInstall: "LambdaFunctionToValidateBeforeTrafficShift"
  - AfterInstall: "LambdaFunctionToValidateAfterTrafficShift"
  - AfterAllowTestTraffic: "LambdaFunctionToValidateTestTraffic"
  - BeforeAllowTraffic: "LambdaFunctionToValidateBeforeAllowTraffic"
  - AfterAllowTraffic: "LambdaFunctionToValidateAfterAllowTraffic"
```

The switch example assumes curl inside the application container and local jq. Test the green endpoint separately, preserve the old selector for rollback, and verify service endpoints and external health after switching. The Istio example below needs a service selecting both stable and canary pods; do not reuse the color-restricted blue/green selector.

## Canary Deployment

### Kubernetes with Istio

```yaml
# VirtualService for traffic splitting
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: myapp
spec:
  hosts:
  - myapp
  http:
  - match:
    - headers:
        x-canary:
          exact: "true"
    route:
    - destination:
        host: myapp
        subset: canary
  - route:
    - destination:
        host: myapp
        subset: stable
      weight: 90
    - destination:
        host: myapp
        subset: canary
      weight: 10
---
apiVersion: networking.istio.io/v1beta1
kind: DestinationRule
metadata:
  name: myapp
spec:
  host: myapp
  subsets:
  - name: stable
    labels:
      version: stable
  - name: canary
    labels:
      version: canary
```

### Argo Rollouts

```yaml
apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: myapp
spec:
  replicas: 5
  strategy:
    canary:
      steps:
      - setWeight: 10
      - pause: {duration: 5m}
      - setWeight: 25
      - pause: {duration: 5m}
      - setWeight: 50
      - pause: {duration: 5m}
      - setWeight: 75
      - pause: {duration: 5m}
      analysis:
        templates:
        - templateName: success-rate
        startingStep: 2
        args:
        - name: service-name
          value: myapp
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myapp:v2.0.0
        ports:
        - containerPort: 8080
---
apiVersion: argoproj.io/v1alpha1
kind: AnalysisTemplate
metadata:
  name: success-rate
spec:
  args:
  - name: service-name
  metrics:
  - name: success-rate
    interval: 1m
    successCondition: result[0] >= 0.95
    failureLimit: 3
    provider:
      prometheus:
        address: http://prometheus:9090
        query: |
          sum(rate(http_requests_total{service="{{args.service-name}}",status=~"2.*"}[5m]))
          /
          sum(rate(http_requests_total{service="{{args.service-name}}"}[5m]))
```

## Rolling Deployment

### Kubernetes Default

```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  replicas: 5
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1        # Max pods above desired
      maxUnavailable: 0   # Max pods unavailable
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myapp:v2.0.0
        ports:
        - containerPort: 8080
        readinessProbe:
          httpGet:
            path: /ready
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 10
```

### Rolling Update Commands

```bash
# Update image
kubectl set image deployment/myapp myapp=myapp:v2.0.0

# Watch rollout
kubectl rollout status deployment/myapp

# Pause rollout
kubectl rollout pause deployment/myapp

# Resume rollout
kubectl rollout resume deployment/myapp

# Rollback
kubectl rollout undo deployment/myapp

# Rollback to specific revision
kubectl rollout undo deployment/myapp --to-revision=2

# View history
kubectl rollout history deployment/myapp
```

## Health Checks

### Comprehensive Health Endpoint

```python
# Flask health endpoint
from flask import Flask, jsonify
import psycopg2
import redis
import os
DATABASE_URL = os.environ["DATABASE_URL"]
REDIS_URL = os.environ["REDIS_URL"]

app = Flask(__name__)

@app.route('/health')
def health():
    """Liveness probe - is the app running?"""
    return jsonify({'status': 'healthy'}), 200

@app.route('/ready')
def ready():
    """Readiness probe - can the app serve traffic?"""
    checks = {}
    
    # Database check
    try:
        conn = psycopg2.connect(DATABASE_URL, connect_timeout=3)
        conn.close()
        checks['database'] = 'ok'
    except Exception as e:
        checks['database'] = 'unavailable'
        return jsonify({'status': 'unhealthy', 'checks': checks}), 503
    
    # Redis check
    try:
        r = redis.from_url(REDIS_URL, socket_connect_timeout=3, socket_timeout=3)
        r.ping()
        checks['redis'] = 'ok'
    except Exception as e:
        checks['redis'] = 'unavailable'
        return jsonify({'status': 'unhealthy', 'checks': checks}), 503
    
    return jsonify({'status': 'healthy', 'checks': checks}), 200
```


## Contents

- [Rollback Procedures](references/details.md)
- [Rollback Checklist](references/details.md)
- [Common Issues](references/details.md)
- [Best Practices](references/details.md)
- [Related Skills](references/details.md)

## When to Use This Skill

Use this skill when:
- Implementing zero-downtime deployments
- Reducing deployment risk
- Enabling instant rollbacks
- Running canary releases
- Performing A/B testing in production

## Limitations

- Guidance executes against real environments: confirm target, blast radius, and rollback plan before applying anything.
- Never deploy to production without explicit approval. Docs-only import: upstream scripts and templates not bundled.

### Example

```bash
git status && git diff --stat
kubectl diff -f manifest.yaml
```

> Adapted from [BagelHole/DevOps-Security-Agent-Skills](https://github.com/BagelHole/DevOps-Security-Agent-Skills) (MIT); frontmatter, When to Use/Limitations, and safety boundaries added for upstream compliance. Docs-only import: helper scripts and templates not bundled.