KubernetesのimagePullPolicy機能の動作確認

目的

kubernetesのcontainerのimageの取得する/しない動作を確認する。
deploymentにimagePullPolicyで設定する

事前準備: internet reachが無い状態にする

bash

vagrant@vagrant:~/jira$ ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
From 10.0.2.2 icmp_seq=1 Destination Net Unreachable
From 10.0.2.2 icmp_seq=2 Destination Net Unreachable
^C
--- 8.8.8.8 ping statistics ---
6 packets transmitted, 0 received, +6 errors, 100% packet loss, time 5117ms

vagrant@vagrant:~/jira$

deploymentで使うimageをlocalのnodeの落としておく

bash

vagrant@vagrant:~/jira$ docker images | grep d058fe5de8ce
atlassian/jira-software                 latest              d058fe5de8ce        3 days ago          634MB
vagrant@vagrant:~/jira$

deploymentにIfNotPresentをconfigしていない場合 => ErrImagePullになる

bash

vagrant@vagrant:~/jira$ cat jira-deployment-svc.yaml | grep image
      - image: atlassian/jira-software
        # imagePullPolicy: IfNotPresent
vagrant@vagrant:~/jira$ kubectl apply -f jira-deployment-svc.yaml
deployment.apps/jira created
service/jira created
vagrant@vagrant:~/jira$ kubectl get pod -n jira -w
NAME                    READY   STATUS             RESTARTS   AGE
jira-66c5d87466-lqprz   0/1     ImagePullBackOff   0          6s
jira-66c5d87466-lqprz   0/1     ErrImagePull       0          31s
jira-66c5d87466-lqprz   0/1     ImagePullBackOff   0          44s
^Cvagrant@vagrant:~/jira$

一旦deploymentを消す

bash

vagrant@vagrant:~/jira$ kubectl delete -f jira-deployment-svc.yaml
deployment.apps "jira" deleted
service "jira" deleted

今度はdeplymentにIfNotPresentをconfigしている場合 => podがrunningになる

bash

vagrant@vagrant:~/jira$ cat jira-deployment-svc.yaml | grep image
      - image: atlassian/jira-software
        imagePullPolicy: IfNotPresent
vagrant@vagrant:~/jira$ kubectl apply -f jira-deployment-svc.yaml
deployment.apps/jira created
service/jira created
vagrant@vagrant:~/jira$ kubectl get pod -n jira
NAME                    READY   STATUS    RESTARTS   AGE
jira-5d59fdd6c6-npmfk   1/1     Running   0          5s
vagrant@vagrant:~/jira$

結論

imagePullPolicyをIfNotPresentにすれば、imageがlocalにあれば再度pullしてくる事は無い。