[Kubernetes] Kubernetes Management Techniques

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Kubernetes Management Techniques

• YAML Generators in kubectl commands
• Imperative vs Desclarative
• Three Management Approaches

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YAML Generators in kubectl commands

• kubectl create use helper templates called generators
  • Generators can have different defaults by version
• Every resource in k8s has a specification(spec)

# see the deployment templates with --dry-run=client -o yaml
kubectl create deployment test --image nginx --dry-run=client -o yaml

# see the job templates with --dry-run=client -o yaml
kubectl create job test --image nginx --dry-run=client -o yaml

# see the service templates with --dry-run=client -o yaml
kubectl create deployment test --image nginx # deployment needed to expose
kubectl expose deploy test --port 80 --dry-run=client -o yaml

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Imperative vs Desclarative

• Imperative: Focuses on how a program operates
  • For example, boil water, get 42 gram of medium-fine grounds, and poor over 700 grams of water, etc
  • In k8s, the command lines (kubectl run | create | update | etc. ) are imperative
• Desclarative: Focuses on what a program should accomplish
  • For example, “Barista i’d like a cup of coffee”
  • In k8s, yaml find can be used(kubectl apply -f values.yaml)

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Three Management Approaches

• Imperative commands: kubectl run | expose | scale | edit | create deployment | etc.
  • Best for dev/learning/personal projects
  • Easy to learn, hardest to manage
• Imperative objects: create | replace -f values.yaml, etc.
  • Good for prod of small environments, single file per command
  • Store changes in git-based yaml files
• Declarative: apply -f values.yaml | dir/ | diff
  • Best for prod, easier to automate
  • Harder to understand and predict changes

• Do not mix the approaches in production!