(CKA) 04. Application Lifecycle Management

CKA를 준비하면서 공부한 요약 내용입니다.

Rollout and Versioning

Rollout Command

kubectl rollout status deployment/myapp-deployment
kubectl rollout history deployment/myapp-deployment

Deployment Strategy

Recreate

destruction 5
create 5

Rolling Update

→ default strategy

destruction and create one by one

Revision

kubectl apply -f deployment.yaml
kubectl set image deployment/myapp-deployment nginx=nginx:1.9.1

Upgrades

make new replicaset when upgrade deploy

Rollback

kubectl rollout undo deployment/myapp-deployment
before rollback vs after rollback

Commands and Arguments

docker

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From Ubuntu
Entrypoint ["sleep"]
cmd ["5"]

definition

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apiVersion: v1
kind: Pod
metadata:
  name: ubuntu-sleeper-pod
spec:
  containers:
    - name: ubuntu-sleeper
      image: ubuntu-sleeper
      command: ["sleep2.0"]
      args: ["10"]

Environment

plain Key Value

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env:
  - name: APP_COLOR
    value: pink

configMap

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env:
  - name: APP_COLOR
    valueFrom:
      configMapKeyRef:

Secrets

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env:
  - name: APP_COLOR
    valueFrom:
      secretKeyRef:

ConfigMaps

create ConfigMap
Inject into pod

create

imperative

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kubectl create configmap\\
  app-config --from-literal=APP_COLOR=blue \\
            --from-literal=APP_MODE=prod

kubectl create configmap app-config --from-file=<path-to-file>

declartive

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apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  APP_COLOR: blue
  APP_MODE: prod

view

kubectl get configmaps
kubectl describe configmaps

ConfigMap in Pods

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apiVersion: v1
kind: Pod
metadata:
  name: simple-webapp-color
spec:
  containers:
    - name: simple-webapp-color
      image: simple-webapp-color
      envFrom:
        - configMapRef:
            name: app-config

Secrets

create secret
inject into pod

create

imperative

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kubectl create secret generic\\
  <secret-name> --from-literal=<key>=<value>

kubectl create secret <secret-name> --from-file=<path-to-file>

declartive

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apiVersion: v1
kind: Secret
metadata:
  name: app-secret
data:
  DB_Host: mysql
  DB_User: root
  DB_Passwird: paswrd

data → encoded format for safe
echo -n 'mysql' | base64

view

kubectl get secrets
kubectl describe secrets

decode

echo -n 'abalksdfas=' | base54 --decode

Secrets in Pods

defintion

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apiVersion: v1
kind: Pod
metadata:
  name: simple-webapp-color
spec:
  containers:
    - name: simple-webapp-color
      image: simple-webapp-color
      envFrom:
        - configMapRef:
            name: app-secret

env

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envFrom:
  - secretRef:
      name: app-config

single env

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env:
  - name: DB_Password
    valueFrom:
      secretKeyRef:
        name: app-secret
        key: DB_Password

volume

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volumes:
- name: app-secret-volumne
  secret:
    secretName: app-secret

inside the container

list
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ls /opt/app-secret-volumes

content

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cat /opt/app-secret-volumes/DB_Password

InitContainers

In multi-container pod, want to run a process that runs to completion in a container

initContainer

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apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: busybox:1.28
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']
  initContainers:
  - name: init-myservice
    image: busybox
    command: ['sh', '-c', 'git clone <some-repository-that-will-be-used-by-application> ; done;']

multiple initContainers

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apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: busybox:1.28
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', 'until nslookup myservice; do echo waiting for myservice; sleep 2; done;']
  - name: init-mydb
    image: busybox:1.28
    command: ['sh', '-c', 'until nslookup mydb; do echo waiting for mydb; sleep 2; done;']