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Deployments

Its just a Replicaset, with more features, like rollback and rollout

Deployments are simply objects that encapsulate ReplicaSets, allowing definitions around rolling Updates, undo changes, pause and resume

Identical specs

You can cat replicaSet.yaml | sed 's/ReplicaSet/Deployment/' a ReplicaSet definition to turn it into a Deployment.

Template​

apiVersion: apps/v1
kind: Deployment
metadata:
  name: ${RESOURCE_NAME}
  namespace: default
  labels: &app_labels
    name: ${RESOURCE_NAME}
spec:
  selector:
    matchLabels:
      <<: *app_labels
  replicas: 1
  template:
    metadata:
      name: ${RESOURCE_NAME}
      labels:
        <<: *app_labels
    spec:
      containers:
        - name: ${RESOURCE_NAME}
          image: localhost:30000/${RESOURCE_NAME}:latest

Rollout​

A new deployment triggers a rollout, which triggers a new deployment revision (rev 1). When the container version is outdated, a new rollout is created (rev 2).

kubectl rollout status
kubectl rollout history {deployment-name}

Types of Deployment Strategies​

  • Recreate: Destroy then create (causes downtime) (Scale down replica set to 0 first)
  • Rolling Update: Take one down, upgrade it around (upgrade it)

Can also use

kubectl set image deployment/{deployment-name} container=image:latest

K8s creates a new replica set when you update your deployment.

Rollback (Uhoh!)​

kubectl rollout undo deployment/<deployment-name>