kubernetes rolling update

Rolling update

1. Create Deployment

# kubectl apply -f wether.cm.yaml
# kubectl apply -f weather-jmx.deploy.yaml --record

產生了新的rs 。

[root@k8s-master ~]# kubectl get rs -w | egrep "jmx|NAME"
NAME                    DESIRED     CURRENT     READY       AGE
weather-jmx-1809594718   3           3           3          35s

2. Update image

模擬版本升級，更換deployment 中使用的鏡像。

這裏以直接修改yaml文件爲例：
用文本編輯器打開weather-jmx.deploy.yaml， 將鏡像改爲：

172.16.18.5:30088/admin/centos7.1-v1-wth:test

執行：

[root@k8s-master ~]# kubectl replace -f weather-jmx.deploy.yaml --record
deployment "weather-jmx" replaced

3. Observation

[root@k8s-master ~]# kubectl get rs -w | egrep "jmx"
weather-jmx-1809594718        3         3         3         52s
weather-jmx-790510206   1         0         0         0s
weather-jmx-1809594718   2         3         3         9m
weather-jmx-790510206   1         0         0         0s
weather-jmx-790510206   1         1         0         0s
weather-jmx-1809594718   2         3         3         9m
weather-jmx-1809594718   2         2         2         9m
weather-jmx-790510206   2         1         0         0s
weather-jmx-790510206   2         1         0         0s
weather-jmx-790510206   2         2         0         0s
weather-jmx-790510206   2         2         1         4s
weather-jmx-1809594718   1         2         2         9m
weather-jmx-1809594718   1         2         2         9m
weather-jmx-790510206   3         2         1         4s
weather-jmx-1809594718   1         1         1         9m
weather-jmx-790510206   3         2         1         4s
weather-jmx-790510206   3         3         1         4s
weather-jmx-790510206   3         3         2         6s
weather-jmx-1809594718   0         1         1         9m
weather-jmx-1809594718   0         1         1         9m
weather-jmx-1809594718   0         0         0         9m
weather-jmx-790510206   3         3         3         7s

通過 kubectl get rs -w 命令可以觀察到,更新鏡像後創建了一個新的rs.
從上圖可以看出，新的rs 從1開始，逐漸的替換掉來原來的3個pod. 而原來的rs也由3個pod，逐漸變爲0個pod. 由此完成了整個滾動升級的過程。
升級完成

可以通過 rollout history 來查看Deployment的滾動日誌。

[root@k8s-master ~]# kubectl rollout history deployment/weather-jmx
deployments "weather-jmx"
REVISION    CHANGE-CAUSE
1       kubectl apply -f weather-jmx.deploy.yaml --record
2       kubectl replace -f weather-jmx.deploy.yaml --record

4. Rollback

如果需要回退到上個版本，執行：

[root@k8s-master ~]# kubectl rollout undo deployment/weather-jmx
deployment "weather-jmx" rolled back

回退過程同滾動升級過程一致：

[root@k8s-master ~]# kubectl get rs -w | egrep "jmx"
weather-jmx-1809594718        0         0         0         13m
weather-jmx-790510206         3         3         3         3m
weather-jmx-1809594718   0         0         0         13m
weather-jmx-1809594718   1         0         0         13m
weather-jmx-790510206   2         3         3         4m
weather-jmx-1809594718   1         0         0         13m
weather-jmx-1809594718   1         1         0         13m
weather-jmx-790510206   2         3         3         4m
weather-jmx-790510206   2         2         2         4m
weather-jmx-1809594718   2         1         0         13m
weather-jmx-1809594718   2         1         0         13m
weather-jmx-1809594718   2         2         0         13m
weather-jmx-1809594718   2         2         1         13m
weather-jmx-790510206   1         2         2         4m
weather-jmx-790510206   1         2         2         4m
weather-jmx-1809594718   3         2         1         13m
weather-jmx-790510206   1         1         1         4m
weather-jmx-1809594718   3         2         1         13m
weather-jmx-1809594718   3         3         1         13m
weather-jmx-1809594718   3         3         2         13m
weather-jmx-790510206   0         1         1         4m
weather-jmx-790510206   0         1         1         4m
weather-jmx-790510206   0         0         0         4m
weather-jmx-1809594718   3         3         3         13m

[root@k8s-master ~]# kubectl rollout history deployment/weather-jmx
deployments "weather-jmx"
REVISION    CHANGE-CAUSE
2       kubectl replace -f weather-jmx.deploy.yaml --record
3       kubectl apply -f weather-jmx.deploy.yaml --record

通過 rollout history 可以發現，當前的revision 爲3。也可以通過

# kubectl rollout undo deployment/weather-jmx --revision=<REVISION>

來回退到具體某個版本

參考鏈接：

https://kubernetes.io/docs/concepts/workloads/controllers/deployment/

https://tachingchen.com/tw/blog/Kubernetes-Rolling-Update-with-Deployment/