목차

Update APP

이 문서는 Rolling Update / Rollback APP 에 대한 방법을 포함하고 있습니다.

Update Source

아래와 같이 Source 를 UPDATE 가 되었습니다.
신규 Build 및 Image Push 는 build app flask 를 확인하여 진행합니다.

diff --git a/main.py b/main.py
index 2b9f022..9b347b4 100755
--- a/main.py
+++ b/main.py
@@ -8,7 +8,7 @@ podname = os.uname()[1]

 @app.route("/")
 def index():
-    return " Container LAB | POD Working : " + podname + " | v=1\n"
+    return " Container LAB | POD Working : " + podname + " | v=2\n"

 if __name__ == "__main__":
     app.run(host="0.0.0.0", port="80")

시간 관계상 Push 된 이미지를 사용할 것입니다.

  • Container Image Tag : han0495/flask-example-app:v2

Rolling Update

아래 명령을 통해 기존에 v1 에서 v2 로 image 를 변경하여 Rolling Update 해보겠습니다.

  • 기존 정보 
      $ kubectl describe deployments flask-example-app
  ...
  Pod Template:
    Labels:  app=flask-example-app
    Containers:
     flask-example-app:
      Image:        han0495/flask-example-app:v1    <<
      Port:         <none>
      Host Port:    <none>
      Environment:  <none>
      Mounts:       <none>
    Volumes:        <none>
  • Change image 
      $ kubectl set image deployments flask-example-app flask-example-app=han0495/flask-example-app:v2
  • Rolling Update 상태 확인
    • 상태 확인 
        $ kubectl rollout status deployments flask-example-app
  Waiting for deployment "flask-example-app" rollout to finish: 1 old replicas are pending termination...
  Waiting for deployment "flask-example-app" rollout to finish: 1 old replicas are pending termination...
  Waiting for deployment "flask-example-app" rollout to finish: 1 old replicas are pending termination...
  deployment "flask-example-app" successfully rolled out
    • 실제 서비스 확인 
        $ while true; do curl 192.168.200.110:32296; done
   Container LAB | POD Working : flask-example-app-959c5f88d-k95wk | v=1
   Container LAB | POD Working : flask-example-app-959c5f88d-b62j5 | v=1
   Container LAB | POD Working : flask-example-app-677cbdd665-mhpqs | v=2
   Container LAB | POD Working : flask-example-app-677cbdd665-wwmf8 | v=2
   Container LAB | POD Working : flask-example-app-959c5f88d-b62j5 | v=1
   Container LAB | POD Working : flask-example-app-677cbdd665-mhpqs | v=2
   Container LAB | POD Working : flask-example-app-677cbdd665-wwmf8 | v=2
   Container LAB | POD Working : flask-example-app-677cbdd665-mhpqs | v=2
   Container LAB | POD Working : flask-example-app-959c5f88d-k95wk | v=1
   ...
  • 변경 확인 
      $ kubectl describe deployments flask-example-app
  Name:                   flask-example-app
  Namespace:              default
  CreationTimestamp:      Wed, 09 Sep 2020 15:37:59 +0900
  Labels:                 app=flask-example-app
  Annotations:            deployment.kubernetes.io/revision: 2
  Selector:               app=flask-example-app
  Replicas:               5 desired | 5 updated | 5 total | 5 available | 0 unavailable
  StrategyType:           RollingUpdate
  MinReadySeconds:        0
  RollingUpdateStrategy:  25% max unavailable, 25% max surge
  Pod Template:
    Labels:  app=flask-example-app
    Containers:
     flask-example-app:
      Image:        han0495/flask-example-app:v2       <<< 변경됨
      Port:         <none>
      Host Port:    <none>
      Environment:  <none>
      Mounts:       <none>
    Volumes:        <none>
  Conditions:
    Type           Status  Reason
    ----           ------  ------
    Available      True    MinimumReplicasAvailable
    Progressing    True    NewReplicaSetAvailable
  OldReplicaSets:  <none>
  NewReplicaSet:   flask-example-app-677cbdd665 (5/5 replicas created)
  Events:
    Type    Reason             Age    From                   Message
    ----    ------             ----   ----                   -------
    Normal  ScalingReplicaSet  19m    deployment-controller  Scaled up replica set flask-example-app-959c5f88d to 5
    Normal  ScalingReplicaSet  3m31s  deployment-controller  Scaled up replica set flask-example-app-677cbdd665 to 2
    Normal  ScalingReplicaSet  3m31s  deployment-controller  Scaled down replica set flask-example-app-959c5f88d to 4
    Normal  ScalingReplicaSet  3m30s  deployment-controller  Scaled up replica set flask-example-app-677cbdd665 to 3
    Normal  ScalingReplicaSet  2m59s  deployment-controller  Scaled down replica set flask-example-app-959c5f88d to 3
    Normal  ScalingReplicaSet  2m58s  deployment-controller  Scaled up replica set flask-example-app-677cbdd665 to 4
    Normal  ScalingReplicaSet  2m56s  deployment-controller  Scaled down replica set flask-example-app-959c5f88d to 2
    Normal  ScalingReplicaSet  2m55s  deployment-controller  Scaled up replica set flask-example-app-677cbdd665 to 5
    Normal  ScalingReplicaSet  2m50s  deployment-controller  Scaled down replica set flask-example-app-959c5f88d to 1
    Normal  ScalingReplicaSet  2m3s   deployment-controller  Scaled down replica set flask-example-app-959c5f88d to 0

Rollback APP

Rollback 은 배포된 APP 에 문제가 있을 때, 다시 이전 이미지로 배포 해야 되는 경우 사용하는 방법입니다.
(꼭 문제가 있어야 사용이 가능한 것은 아님, 주 목적은 이전 버전으로 Rollback 하기 위함입니다.)

먼저 아래 명령어를 통해 Rolling Update 를 다시 진행합니다.

$ kubectl set image deployments flask-example-app flask-example-app=han0495/flask-example-app:v99

어떤 일이 발생될까요?

$ kubectl get pod
NAME                                 READY   STATUS             RESTARTS   AGE
flask-example-app-677cbdd665-mhpqs   1/1     Running            0          8m33s
flask-example-app-677cbdd665-wwmf8   1/1     Running            0          8m33s
flask-example-app-677cbdd665-x95tn   1/1     Running            0          8m31s
flask-example-app-677cbdd665-754fq   1/1     Running            0          7m59s
flask-example-app-79f5875dcf-26pvs   0/1     ImagePullBackOff   0          38s
flask-example-app-79f5875dcf-thxmx   0/1     ImagePullBackOff   0          38s
flask-example-app-79f5875dcf-jmwpv   0/1     ErrImagePull       0          38s

Image 에 v99 라는 TAG 는 없으므로 ImagePull 에서 Error 가 발생되면서 서비스 배포가 정상적으로 진행이 안됩니다.

  • Rollback 진행
    • 현재 상태 확인 
        $ kubectl rollout history deployment flask-example-app
  deployment.apps/flask-example-app
  REVISION  CHANGE-CAUSE
  1         <none>
  2         <none>
  3         <none>   < 현재 버전
    • Rollback 진행 
        $ kubectl rollout undo deployment flask-example-app
  deployment.apps/flask-example-app rolled back
    • Rollback 확인 
        $ kubectl describe deployments.apps flask-example-app
  Name:                   flask-example-app
  Namespace:              default
  CreationTimestamp:      Wed, 09 Sep 2020 15:37:59 +0900
  Labels:                 app=flask-example-app
  Annotations:            deployment.kubernetes.io/revision: 4
  Selector:               app=flask-example-app
  Replicas:               5 desired | 5 updated | 5 total | 5 available | 0 unavailable
  StrategyType:           RollingUpdate
  MinReadySeconds:        0
  RollingUpdateStrategy:  25% max unavailable, 25% max surge
  Pod Template:
Labels:  app=flask-example-app
Containers:
 flask-example-app:
  Image:        han0495/flask-example-app:v2    <<
  Port:         <none>
  Host Port:    <none>
  • v1 로 돌아가기
    • Rollback 수행 
        $ kubectl rollout undo deployment flask-example-app --to-revision=1
    • 서비스 확인 
        $ while true; do curl 192.168.200.110:32296; done
   Container LAB | POD Working : flask-example-app-959c5f88d-rjbqc | v=1
   Container LAB | POD Working : flask-example-app-959c5f88d-sgrfk | v=1
   Container LAB | POD Working : flask-example-app-959c5f88d-sgrfk | v=1
   Container LAB | POD Working : flask-example-app-959c5f88d-rjbqc | v=1
   Container LAB | POD Working : flask-example-app-677cbdd665-wwmf8 | v=2  <<
   Container LAB | POD Working : flask-example-app-959c5f88d-sgrfk | v=1
   Container LAB | POD Working : flask-example-app-677cbdd665-wwmf8 | v=2  <<
   Container LAB | POD Working : flask-example-app-959c5f88d-rjbqc | v=1
   Container LAB | POD Working : flask-example-app-959c5f88d-l7zjp | v=1
   Container LAB | POD Working : flask-example-app-959c5f88d-sgrfk | v=1
   Container LAB | POD Working : flask-example-app-959c5f88d-l7zjp | v=1
    • Rollback 완료 
        $ kubectl describe deployments.apps flask-example-app
  Name:                   flask-example-app
  Namespace:              default
  CreationTimestamp:      Wed, 09 Sep 2020 15:37:59 +0900
  Labels:                 app=flask-example-app
  Annotations:            deployment.kubernetes.io/revision: 5
  Selector:               app=flask-example-app
  Replicas:               5 desired | 5 updated | 5 total | 5 available | 0 unavailable
  StrategyType:           RollingUpdate
  MinReadySeconds:        0
  RollingUpdateStrategy:  25% max unavailable, 25% max surge
  Pod Template:
Labels:  app=flask-example-app
Containers:
 flask-example-app:
  Image:        han0495/flask-example-app:v1
  Port:         <none>
  Host Port:    <none>
  Environment:  <none>
  Mounts:       <none>
Volumes:        <none>

참고 문서

chhanz's profile image

chhanz

2020-09-28

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