Guides

Kubernetes वर Blue-Green vs Canary (सोप्या शब्दात)

By Ravindra Bagale, DevOps trainer · LinkedIn · Published: 28 October 2026 · Last updated: 28 October 2026

Blue-green: Service selector flip. Canary: थोड्या replicas आधी, मग वाढ किंवा abort.

Language: English · मराठी · हिंदी

दोन शैली का

Release fail; escape हवा.

Why: In-place undo लपवते. What: flip vs percent. How: labels + selector.

Example 1: Blue Deployment

Type this:

mkdir -p /tmp/bgc && printf '%s\n' 'apiVersion: apps/v1' 'kind: Deployment' 'metadata: {name: web-blue}' 'spec:' '  replicas: 2' '  selector: {matchLabels: {app: web, color: blue}}' '  template:' '    metadata: {labels: {app: web, color: blue}}' '    spec: {containers: [{name: web, image: public.ecr.aws/docker/library/nginx:1.27-alpine}]}' > /tmp/bgc/blue.yaml && grep color /tmp/bgc/blue.yaml | head -2

You will see:

selector: {matchLabels: {app: web, color: blue}}

What it means: Blue is the live color today.

Example 2: Green Deployment

Type this:

printf '%s\n' 'apiVersion: apps/v1' 'kind: Deployment' 'metadata: {name: web-green}' 'spec:' '  replicas: 2' '  selector: {matchLabels: {app: web, color: green}}' '  template:' '    metadata: {labels: {app: web, color: green}}' '    spec: {containers: [{name: web, image: public.ecr.aws/docker/library/nginx:1.27-alpine}]}' > /tmp/bgc/green.yaml && grep name /tmp/bgc/green.yaml | head -1

You will see:

metadata: {name: web-green}

What it means: Green sits idle until you flip the Service.

Example 3: Service points to blue

Type this:

printf '%s\n' 'apiVersion: v1' 'kind: Service' 'metadata: {name: web}' 'spec:' '  selector: {app: web, color: blue}' '  ports: [{port: 80}]' > /tmp/bgc/svc.yaml && grep color /tmp/bgc/svc.yaml

You will see:

selector: {app: web, color: blue}

What it means: Flip = change selector to green.

Concept 1: Blue-green

selector बदला.

Why: Half update गोंधळ. What: patch green. How: patch blue = rollback.

Example 4: Blue-green flip command

Type this:

printf '%s\n' 'kubectl patch svc web -p "{\"spec\":{\"selector\":{\"app\":\"web\",\"color\":\"green\"}}"'

You will see:

kubectl patch svc web -p "{"spec":{"selector":{"app":"web","color":"green"}}}"

What it means: All traffic moves in one step — Instant flip.

Example 8: Watch endpoints

Type this:

printf '%s\n' 'kubectl get endpoints web -o wide'

You will see:

kubectl get endpoints web -o wide

What it means: After a flip, endpoints must list the new pods.

Example 9: Rollback blue-green

Type this:

printf '%s\n' 'kubectl patch svc web -p "{\"spec\":{\"selector\":{\"app\":\"web\",\"color\":\"blue\"}}"'

You will see:

kubectl patch svc web -p "{"spec":{"selector":{"app":"web","color":"blue"}}}"

What it means: Flip back — old pods still warm.

Concept 2: Canary

थोडी नवीन pods.

Why: Exact % साठी mesh. What: 9+1 ≈ 10%. How: scale 0 = abort.

Example 5: Canary weight idea

Type this:

printf '%s\n' 'canary: 10 percent pods on new version; 90 percent stay on stable'

You will see:

canary: 10 percent pods on new version; 90 percent stay on stable

What it means: Canary = small blast radius first.

Example 6: Two Deployments one Service (canary labels)

Type this:

printf '%s\n' 'Service selector app=web only; both stable and canary pods share app=web' 'Stable also has track=stable; canary has track=canary'

You will see:

Service selector app=web only; both stable and canary pods share app=web
Stable also has track=stable; canary has track=canary

What it means: Replica counts set the approximate percent.

Example 7: Canary scale math

Type this:

printf '%s\n' 'stable replicas=9; canary replicas=1  → about 10 percent'

You will see:

stable replicas=9; canary replicas=1  → about 10 percent

What it means: Exact percent needs a mesh; replica ratio is the beginner path.

Concept 3: निवड

capacity vs risk.

Why: चुकीची निवड महाग. What: 2× → BG; tight → canary. How: cleanup.

Example 10: Rollback canary

Type this:

printf '%s\n' 'kubectl scale deploy/web-canary --replicas=0'

You will see:

kubectl scale deploy/web-canary --replicas=0

What it means: Remove canary pods; stable keeps 100%.

Example 11: When to pick which

Type this:

printf '%s\n' 'blue-green: need instant rollback and double capacity ok' 'canary: want gradual risk on one cluster capacity'

You will see:

blue-green: need instant rollback and double capacity ok
canary: want gradual risk on one cluster capacity

What it means: Infosys runbooks pick canary when capacity is tight.

Example 12: Cleanup

Type this:

printf '%s\n' 'kubectl delete -f svc.yaml -f blue.yaml -f green.yaml'

You will see:

kubectl delete -f svc.yaml -f blue.yaml -f green.yaml

What it means: Lab cleanup.

Release card

1 two Deploys 2 Service 3 flip/ratio 4 watch 5 rollback

Suppose: empty endpoints

Labels.

Suppose: wrong %

Replica counts.

Check yourself (quiz)

prepare → flip/canary → measure → finish/rollback. Did you understand? Let us try it once more.