kubectl diffを使ってみる

kubernetesのドキュメントを読んでて、kubectl apply -f hoge.ymlはよく使うけど、 kubectl diffを使ってなかったので、どのように表示させれるか気になって試した。

使用した環境

• GKE
• version 1.13.7-gke.19

試す

変更前のmanifest

deployment_old.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 2
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80

変更後のmanifest

deployment_new.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 3 # <- ここを変更する
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80

deployment_oldのapply

$ kubectl apply -f deployment_old.yml
deployment.apps/nginx-deployment created

$ kubectl get pod
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-76bf4969df-c7btx   1/1     Running   0          2m7s
nginx-deployment-76bf4969df-jvnjx   1/1     Running   0          2m7s

deployment_oldとdeployment_newとのdiff

$ kubectl diff -f deployment_new.ymlをしたところ・・・
普通にdiffだった。

diff -u -N /var/folders/3p/67s9vdms1vqd95dyynttcvyr0000gn/T/LIVE-194678655/apps.v1.Deployment.default.nginx-deployment /var/folders/3p/67s9vdms1vqd95dyynttcvyr0000gn/T/MERGED-809569490/apps.v1.Deployment.default.nginx-deployment
--- /var/folders/3p/67s9vdms1vqd95dyynttcvyr0000gn/T/LIVE-194678655/apps.v1.Deployment.default.nginx-deployment	2019-08-20 22:52:12.000000000 +0900
+++ /var/folders/3p/67s9vdms1vqd95dyynttcvyr0000gn/T/MERGED-809569490/apps.v1.Deployment.default.nginx-deployment	2019-08-20 22:52:12.000000000 +0900
@@ -6,7 +6,7 @@
     kubectl.kubernetes.io/last-applied-configuration: |
       {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"name":"nginx-deployment","namespace":"default"},"spec":{"replicas":2,"selector":{"matchLabels":{"app":"nginx"}},"template":{"metadata":{"labels":{"app":"nginx"}},"spec":{"containers":[{"image":"nginx:1.7.9","name":"nginx","ports":[{"containerPort":80}]}]}}}}
   creationTimestamp: "2019-08-20T13:45:17Z"
-  generation: 1
+  generation: 2
   name: nginx-deployment
   namespace: default
   resourceVersion: "1135"
@@ -14,7 +14,7 @@
   uid: bef21344-c350-11e9-8bb0-42010a92004b
 spec:
   progressDeadlineSeconds: 600
-  replicas: 2
+  replicas: 3
   revisionHistoryLimit: 10
   selector:
     matchLabels:
exit status 1

感想

CDのパイプラインでも、diffで確認したあとに、applyってしたほうが安全だし、変更点に気づきやすいんじゃね？と思った。