Updated:
テクニカルブログ

15Stepで習得 Dockerから入るKubernetes その5

ロールアウト・ロールバック

ロールアウト機能

ロールアウトとは、アプリケーションコンテナの更新
サービスが止まらないよう、古いPodと新しいPodを入れ替えることが可能

例）nginxの設定を変更する
手順

  1. nginxの設定を変更
  2. 新しいコンテナイメージとしてビルド
  3. コンテナイメージをリポジトリへ登録する
  4. マニフェストで指定されているコンテナイメージ新しいコンテナイメージに変更する
  5. ロールアウト

マニフェストファイルの作成

変更前のマニフェストをnginx-deployment2.yml、変更後のマニフェストをnignx-deployment3.ymlとする

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$ cat nginx-deployment2.yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-deploy
spec:
  replicas: 5
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: nginx
        image: nginx:1.16

nginxのバージョンは1.16

変更後

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$ cat nginx-deployment3.yml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-deploy
spec:
  replicas: 5
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: nginx
        image: nginx:1.17

違いは

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$ diff -u nginx-deployment2.yml nginx-deployment3.yml
--- nginx-deployment2.yml	2020-03-04 21:39:06.000000000 +0900
+++ nginx-deployment3.yml	2020-03-04 21:40:14.000000000 +0900
@@ -14,4 +14,4 @@
     spec:
       containers:
       - name: nginx
-        image: nginx:1.16
+        image: nginx:1.17

のようにバージョンのみ

マニフェストの適用

まずはnginx-deployment2.ymlから

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$ kubectl apply -f nginx-deployment2.yml
deployment.apps/web-deploy created
$ kubectl get pod
NAME                          READY   STATUS    RESTARTS   AGE
web-deploy-866f97c649-788hf   1/1     Running   0          6s
web-deploy-866f97c649-8hsr8   1/1     Running   0          6s
web-deploy-866f97c649-kfxmg   1/1     Running   0          6s
web-deploy-866f97c649-pqrbf   1/1     Running   0          6s
web-deploy-866f97c649-vrm6r   1/1     Running   0          6s

起動したことがわかる
詳細に見る場合はkubectl describeを利用する

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$ kubectl describe deployment web-deploy
Name:                   web-deploy
Namespace:              default
CreationTimestamp:      Mon, 09 Mar 2020 21:46:59 +0900
Labels:                 <none>
Annotations:            deployment.kubernetes.io/revision: 1
                        kubectl.kubernetes.io/last-applied-configuration:
                          {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"name":"web-deploy","namespace":"default"},"spec":{"replicas":5,"...
Selector:               app=web
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=web
  Containers:
   nginx:
    Image:        nginx:1.16
    Port:         <none>
    Host Port:    <none>
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   web-deploy-866f97c649 (5/5 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  6s    deployment-controller  Scaled up replica set web-deploy-866f97c649 to 5

nginxのimageは1.16

次にnginx-deployment3.ymlを適用する

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$ kubectl apply -f nginx-deployment3.yml
deployment.apps/web-deploy configured
$ kubectl get pods
NAME                          READY   STATUS              RESTARTS   AGE
web-deploy-85477dddcd-4hzs9   0/1     ContainerCreating   0          4s
web-deploy-85477dddcd-4z7bw   0/1     ContainerCreating   0          4s
web-deploy-85477dddcd-crs96   0/1     ContainerCreating   0          4s
web-deploy-866f97c649-5z7r9   0/1     Terminating         0          2m48s
web-deploy-866f97c649-65fpv   1/1     Running             0          2m48s
web-deploy-866f97c649-7j7m6   1/1     Running             0          2m48s
web-deploy-866f97c649-nsw5d   1/1     Running             0          2m48s
web-deploy-866f97c649-vkwxd   1/1     Running             0          2m48s
$ kubectl get pods
NAME                          READY   STATUS    RESTARTS   AGE
web-deploy-85477dddcd-4hzs9   1/1     Running   0          34s
web-deploy-85477dddcd-4z7bw   1/1     Running   0          34s
web-deploy-85477dddcd-5plrj   1/1     Running   0          23s
web-deploy-85477dddcd-848ww   1/1     Running   0          24s
web-deploy-85477dddcd-crs96   1/1     Running   0          34s

数十秒で入れ替わったことがわかる

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$ kubectl describe deployment web-deploy
Name:                   web-deploy
Namespace:              default
CreationTimestamp:      Mon, 09 Mar 2020 21:46:59 +0900
Labels:                 <none>
Annotations:            deployment.kubernetes.io/revision: 2
                        kubectl.kubernetes.io/last-applied-configuration:
                          {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"name":"web-deploy","namespace":"default"},"spec":{"replicas":5,"...
Selector:               app=web
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=web
  Containers:
   nginx:
    Image:        nginx:1.17
    Port:         <none>
    Host Port:    <none>
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   web-deploy-85477dddcd (5/5 replicas created)
Events:
  Type    Reason             Age    From                   Message
  ----    ------             ----   ----                   -------
  Normal  ScalingReplicaSet  4m24s  deployment-controller  Scaled up replica set web-deploy-866f97c649 to 5
  Normal  ScalingReplicaSet  100s   deployment-controller  Scaled up replica set web-deploy-85477dddcd to 2
  Normal  ScalingReplicaSet  100s   deployment-controller  Scaled down replica set web-deploy-866f97c649 to 4
  Normal  ScalingReplicaSet  100s   deployment-controller  Scaled up replica set web-deploy-85477dddcd to 3
  Normal  ScalingReplicaSet  90s    deployment-controller  Scaled down replica set web-deploy-866f97c649 to 3
  Normal  ScalingReplicaSet  90s    deployment-controller  Scaled up replica set web-deploy-85477dddcd to 4
  Normal  ScalingReplicaSet  89s    deployment-controller  Scaled down replica set web-deploy-866f97c649 to 2
  Normal  ScalingReplicaSet  89s    deployment-controller  Scaled up replica set web-deploy-85477dddcd to 5
  Normal  ScalingReplicaSet  88s    deployment-controller  Scaled down replica set web-deploy-866f97c649 to 1
  Normal  ScalingReplicaSet  85s    deployment-controller  (combined from similar events): Scaled down replica set web-deploy-866f97c649 to 0

nginxのimageが1.17になっているのがわかる。またEventsにロールアウトの履歴が残っていることがわかる

ロールバック機能

Kubernetesにおけるロールバック機能は「ロールアウト前の古いコンテナへ戻すためにPodを入れ替えること」をさす

ロールバックコマンド

以下の1行で実行できる

1
kubectl rollout undo deployment デプロイメント名

実際に実行してみる

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$ kubectl rollout undo deployment web-deploy
deployment.apps/web-deploy rolled back
$ kubectl get pods
NAME                          READY   STATUS              RESTARTS   AGE
web-deploy-85477dddcd-4hzs9   0/1     Terminating         0          11m
web-deploy-85477dddcd-4z7bw   1/1     Running             0          11m
web-deploy-85477dddcd-5plrj   1/1     Terminating         0          11m
web-deploy-85477dddcd-848ww   1/1     Terminating         0          11m
web-deploy-85477dddcd-crs96   1/1     Terminating         0          11m
web-deploy-866f97c649-2sfv5   0/1     ContainerCreating   0          2s
web-deploy-866f97c649-nwv7d   0/1     ContainerCreating   0          2s
web-deploy-866f97c649-qhvdr   1/1     Running             0          4s
web-deploy-866f97c649-xskvq   1/1     Running             0          5s
web-deploy-866f97c649-xw4zq   1/1     Running             0          5s
$ kubectl get pods
NAME                          READY   STATUS        RESTARTS   AGE
web-deploy-85477dddcd-4z7bw   1/1     Terminating   0          11m
web-deploy-866f97c649-2sfv5   1/1     Running       0          7s
web-deploy-866f97c649-nwv7d   1/1     Running       0          7s
web-deploy-866f97c649-qhvdr   1/1     Running       0          9s
web-deploy-866f97c649-xskvq   1/1     Running       0          10s
web-deploy-866f97c649-xw4zq   1/1     Running       0          10s
$ kubectl get pods
NAME                          READY   STATUS    RESTARTS   AGE
web-deploy-866f97c649-2sfv5   1/1     Running   0          12s
web-deploy-866f97c649-nwv7d   1/1     Running   0          12s
web-deploy-866f97c649-qhvdr   1/1     Running   0          14s
web-deploy-866f97c649-xskvq   1/1     Running   0          15s
web-deploy-866f97c649-xw4zq   1/1     Running   0          15s

実際に動いているバージョンを確認する

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$ kubectl describe deployment web-deploy
Name:                   web-deploy
Namespace:              default
CreationTimestamp:      Mon, 09 Mar 2020 21:46:59 +0900
Labels:                 <none>
Annotations:            deployment.kubernetes.io/revision: 3
                        kubectl.kubernetes.io/last-applied-configuration:
                          {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"name":"web-deploy","namespace":"default"},"spec":{"replicas":5,"...
Selector:               app=web
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=web
  Containers:
   nginx:
    Image:        nginx:1.16
    Port:         <none>
    Host Port:    <none>
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   web-deploy-866f97c649 (5/5 replicas created)
Events:
  Type    Reason             Age                From                   Message
  ----    ------             ----               ----                   -------
  Normal  ScalingReplicaSet  12m                deployment-controller  Scaled up replica set web-deploy-85477dddcd to 2
  Normal  ScalingReplicaSet  12m                deployment-controller  Scaled down replica set web-deploy-866f97c649 to 4
  Normal  ScalingReplicaSet  12m                deployment-controller  Scaled up replica set web-deploy-85477dddcd to 3
  Normal  ScalingReplicaSet  12m                deployment-controller  Scaled down replica set web-deploy-866f97c649 to 3
  Normal  ScalingReplicaSet  12m                deployment-controller  Scaled up replica set web-deploy-85477dddcd to 4
  Normal  ScalingReplicaSet  11m                deployment-controller  Scaled down replica set web-deploy-866f97c649 to 2
  Normal  ScalingReplicaSet  11m                deployment-controller  Scaled up replica set web-deploy-85477dddcd to 5
  Normal  ScalingReplicaSet  11m                deployment-controller  Scaled down replica set web-deploy-866f97c649 to 1
  Normal  ScalingReplicaSet  11m                deployment-controller  (combined from similar events): Scaled down replica set web-deploy-866f97c649 to 0
  Normal  ScalingReplicaSet  32s                deployment-controller  Scaled up replica set web-deploy-866f97c649 to 2
  Normal  ScalingReplicaSet  32s                deployment-controller  Scaled down replica set web-deploy-85477dddcd to 4
  Normal  ScalingReplicaSet  31s                deployment-controller  Scaled up replica set web-deploy-866f97c649 to 3
  Normal  ScalingReplicaSet  29s (x2 over 14m)  deployment-controller  Scaled up replica set web-deploy-866f97c649 to 5
  Normal  ScalingReplicaSet  29s                deployment-controller  Scaled down replica set web-deploy-85477dddcd to 3
  Normal  ScalingReplicaSet  29s                deployment-controller  Scaled up replica set web-deploy-866f97c649 to 4
  Normal  ScalingReplicaSet  29s                deployment-controller  Scaled down replica set web-deploy-85477dddcd to 2
  Normal  ScalingReplicaSet  29s                deployment-controller  Scaled down replica set web-deploy-85477dddcd to 1
  Normal  ScalingReplicaSet  23s                deployment-controller  Scaled down replica set web-deploy-85477dddcd to 0

1.16に戻っていることがわかる

ロールアウト、ロールバック機能はサービスを停止することなくリリースを行うことができる
実際にアクセスできるサービスを立ち上げないと実感がわかないので、次はServiceについて調べてみる