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Deployment

Deployment Object

  • deployment (has all revision history)
  • replicationSet-1 (revison=1)
  • replicationSet-2 (revison=2)
  • ...
  • replicationSet-n (current)
  • concept:
  • deploy pod/s
  • upgrade (upgrade all pods together)
  • rollout (upgrade pods one after another)
  • rollback
  • pause and resume
  • yaml is same as rs

  • just update kind to deployment object.

  • some command 

      - kubectl get deployments

  - kubectl create deployment --image=nginx nginx

  - kubectl create deployment --image=nginx nginx --dry-run -o yaml > def.yaml

  - kubectl scale deployment nginx --replicas=4

  - kubectl edit deployment d1  :)
    - With Deployments, you can easily edit "any" field/property of the POD template. 
    - unlike pod edit, few feilds can edit.
    - Since the pod template is a child of the deployment specification, 
    - the deployment will automatically delete and create a new pod with the new changes.

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understand yaml

properties

  • progressDeadlineSeconds: 600 , terminationGraceperiodSeconds: 30
  • revisionHistoryLimit : 10
  • strategy
  • rollingUpdate
    • maxSurge:
    • maxUnavailable:
  • type: recreate / rollingUpdate *
  • dnsPolicy: clusterFirst
  • how DNS resolution is handled within the pod.
  • clusterFirst :
    • Uses the cluster’s DNS service first for resolution.
    • If the DNS query fails, it will fall back to the host’s DNS.
  • Default : host’s DNS
  • None

annotations (ignore)

  • kubectl.kubernetes.io/restartedAt: Used to trigger a manual restart of the pods within the Deployment. Setting this annotation to a new timestamp forces a rollout restart, commonly used for manual updates without changing the Deployment spec.
  • prometheus.io/scrape
  • prometheus.io/port: Often used in Deployments where Prometheus monitoring is set up. Setting prometheus.io/scrape: "true" tells Prometheus to scrape metrics, and prometheus.io/port specifies the port to scrape from.
  • app.kubernetes.io/name,
  • app.kubernetes.io/version,
  • app.kubernetes.io/component: These labels are often applied as annotations for organizational purposes, helping to identify the application's name, version, and component type, improving tracking and monitoring.
  • sidecar.istio.io/inject: Common in clusters with Istio service mesh. Setting sidecar.istio.io/inject: "false" on a Deployment prevents Istio from injecting its sidecar container, useful for excluding specific pods from the mesh.
  • checksum/config
  • checksum/secret: Used to force a Deployment rollout when ConfigMaps or Secrets change. By updating the checksum when there are updates, Kubernetes detects a change and re-deploys the pods.