Deployments and Services
Run replicas and expose them with Services. Results appear in the same fence: same-line # comments when short, multiline # blocks below the sample when not. Fences are bash, dockerfile, or yaml as appropriate.
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Run replicas and expose them with Services. Results appear in the same fence: same-line # comments when short, multiline # blocks below the sample when not. Fences are bash, dockerfile, or yaml as appropriate.
Declarative replica management.
apiVersion: apps/v1
kind: Deployment
metadata:
name: api
spec:
replicas: 3
selector:
matchLabels: { app: api }
template:
metadata:
labels: { app: api }
spec:
containers:
- name: api
image: ghcr.io/acme/api:1.0
# 3 pods desiredScale desired count.
spec:
replicas: 5
# kubectl scale deploy/api --replicas=5Max unavailable/surge during rollout.
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 0
maxSurge: 1
# zero-downtime style rolloutStable virtual IP inside the cluster.
apiVersion: v1
kind: Service
metadata:
name: api
spec:
selector: { app: api }
ports:
- port: 80
targetPort: 8080
# ClusterIP allocatedExternal exposure types.
spec:
type: LoadBalancer
ports:
- port: 80
targetPort: 8080
# cloud LB or NodePort fallbackNo ClusterIP for direct pod DNS.
spec:
clusterIP: None
selector: { app: zk }
# dns: pod-ip.svcDNS CNAME Service.
spec:
type: ExternalName
externalName: db.example.com
# resolves to external hostClientIP stickiness.
spec:
sessionAffinity: ClientIP
# same client IP -> same pod (best effort)Labels on Deployment vs pod template.
metadata:
labels: { app: api }
spec:
template:
metadata:
labels: { app: api, version: v1 }
# Service selects pod labelsDelay availability during rollout.
spec:
minReadySeconds: 10
# pod must be ready 10s to countFail rollout if stuck.
spec:
progressDeadlineSeconds: 600
# ProgressDeadlineExceeded conditionHow many old ReplicaSets to keep.
spec:
revisionHistoryLimit: 5
# rollout undo targetsNamed ports for clarity.
ports:
- name: http
port: 80
targetPort: http
# targetPort can be name or numberService without selector - manual Endpoints.
# Service with no selector + Endpoints object
# for external backendsInclude not-ready pods in Endpoints.
publishNotReadyAddresses: true
# useful for stateful joinersStack versions: Kubernetes 1.36.2 · Docker Engine 29.6.1 · Helm 3 · Compose v2 · containerd via CRI
Reviewed by Chris St. John·Last updated Jul 18, 2026