linux运维、架构之路-K8s滚动更新及回滚

一、滚动更新

       应用程序一次只更新一小部分副本,更新成功后,再更新更多的副本,最终完成所有副本的更新。 滚动更新的优点:零停机,整个更新过程始终有副本在运行,从而保证了业务的连续性。

1、创建三个副本Httpd服务,初始镜像为httpd:2.2.31,然后滚动更新至httpd:2.2.32

###cat httpd.yaml###
apiVersion: apps/v1beta2
kind: Deployment
metadata:
name: httpd
spec:
replicas:
selector:
matchLabels:
app: httpd
template:
metadata:
labels:
app: httpd
spec:
containers:
- name: httpd
image: httpd:2.2.
imagePullPolicy: IfNotPresent #默认值,本地有则使用本地镜像,不拉取
ports:
- containerPort:

①创建

kubectl apply -f httpd.yaml

②查看

linux运维、架构之路-K8s滚动更新及回滚

③修改deployment文件进行更新

linux运维、架构之路-K8s滚动更新及回滚

 应用

kubectl apply -f httpd.yaml --record

④再次查看更新后的httpd版本

linux运维、架构之路-K8s滚动更新及回滚

⑤使用命令查看滚动更新详细

kubectl describe deployment httpd

linux运维、架构之路-K8s滚动更新及回滚

 结果:每次只更新替换一个pod副本

⑥使用命令替换镜像

kubectl set image deployments/httpd httpd=httpd:2.2.

⑦验证如下:

[root@k8s-node1 rolling]# kubectl get deployment -o wide
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
httpd 42m httpd httpd:2.2. app=httpd
mtomcat 4d mtomcat liujixiao/java-demo:latest app=mtomcat
mynginx 9d mynginx nginx:latest name=mynginx
mytomcat 9d mytomcat tomcat: app=mytomcat
nginx 16d nginx nginx:latest name=nginx
[root@k8s-node1 rolling]# kubectl get rs -o wide
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
httpd-7584b484ff 11m httpd httpd:2.2. app=httpd,pod-template-hash=
httpd-cb5f5c5cb 38s httpd httpd:2.2. app=httpd,pod-template-hash=
httpd-fbdc45d78 42m httpd httpd:2.2. app=httpd,pod-template-hash=
mtomcat-7d6b5577b9 4d mtomcat tomcat: app=mtomcat,pod-template-hash=
mtomcat-b8d9c579 3d mtomcat liujixiao/java-demo:latest app=mtomcat,pod-template-hash=
mynginx-7659f869f4 9d mynginx nginx:latest name=mynginx,pod-template-hash=
mytomcat-698fb6789 9d mytomcat tomcat: app=mytomcat,pod-template-hash=
nginx-5bc649579b 5d nginx nginx:latest name=nginx,pod-template-hash=
nginx-fd7dc4fbc 16d nginx nginx:latest name=nginx,pod-template-hash=

二、回滚

kubectl apply每次更新应用时,都会记录下当前的配置文件,保存为一个revision (版本),这样就可以通过这个版本回滚到特定的时间。默认配置下,K8s只会保留最近的几个revision,可以在Deployment配置文件中通过revisionHistoryLimit属性增加reviseion数量。

1、实践回滚功能

①创建三个应用配置文件httpd-v1.yaml、httpd-v2.yaml、httpd-v3.yaml

httpd-v1.yaml

apiVersion: apps/v1beta2
kind: Deployment
metadata:
name: httpd
spec:
revisionHistoryLimit:
replicas:
selector:
matchLabels:
app: httpd
template:
metadata:
labels:
app: httpd
spec:
containers:
- name: httpd
image: httpd:2.4.
imagePullPolicy: IfNotPresent #默认值,本地有则使用本地镜像,不拉取
ports:
- containerPort:

httpd-v2.yaml

apiVersion: apps/v1beta2
kind: Deployment
metadata:
name: httpd
spec:
revisionHistoryLimit:
replicas:
selector:
matchLabels:
app: httpd
template:
metadata:
labels:
app: httpd
spec:
containers:
- name: httpd
image: httpd:2.4.
imagePullPolicy: IfNotPresent #默认值,本地有则使用本地镜像,不拉取
ports:
- containerPort:

httpd-v3.yaml

apiVersion: apps/v1beta2
kind: Deployment
metadata:
name: httpd
spec:
revisionHistoryLimit:
replicas:
selector:
matchLabels:
app: httpd
template:
metadata:
labels:
app: httpd
spec:
containers:
- name: httpd
image: httpd:2.4.
imagePullPolicy: IfNotPresent #默认值,本地有则使用本地镜像,不拉取
ports:
- containerPort:

②通过kubectl apply部署并更新应用

kubectl apply -f httpd-v1.yaml --record
deployment.apps "httpd" created
[root@k8s-node1 rolling]# kubectl get deployment httpd -o wide
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
httpd 16s httpd httpd:2.4. app=httpd
[root@k8s-node1 rolling]# kubectl apply -f httpd-v2.yaml --record
deployment.apps "httpd" configured
[root@k8s-node1 rolling]#
[root@k8s-node1 rolling]#
[root@k8s-node1 rolling]# kubectl get deployment httpd -o wide
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
httpd 27s httpd httpd:2.4. app=httpd
[root@k8s-node1 rolling]# kubectl apply -f httpd-v3.yaml --record
deployment.apps "httpd" configured
[root@k8s-node1 rolling]#
[root@k8s-node1 rolling]#
[root@k8s-node1 rolling]#
[root@k8s-node1 rolling]# kubectl get deployment httpd -o wide
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
httpd 36s httpd httpd:2.4. app=httpd
--record的作用是将当前命令记录到revision 记录中,这样我们就可以知道每个revison对应的是哪个配置文件,
通过
kubectl rollout history deployment httpd查看历史记录,如下图:
[root@k8s-node1 rolling]# kubectl rollout history deployment httpd
deployments "httpd"
REVISION CHANGE-CAUSE
kubectl apply --filename=httpd-v1.yaml --record=true
kubectl apply --filename=httpd-v2.yaml --record=true
kubectl apply --filename=httpd-v3.yaml --record=true

③回滚到某个版本

查看当前版本:

[root@k8s-node1 rolling]# kubectl get deployment httpd -o wide
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
httpd 17m httpd httpd:2.4. app=httpd

回滚版本

kubectl rollout undo deployment httpd --to-revision=

查看回滚后版本

[root@k8s-node1 rolling]# kubectl get deployment httpd -o wide
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
httpd 19m httpd httpd:2.4. app=httpd

此时再查看历史记录也会发生相应的变化:

[root@k8s-node1 rolling]# kubectl rollout history deployment httpd
deployments "httpd"
REVISION CHANGE-CAUSE
kubectl apply --filename=httpd-v2.yaml --record=true
kubectl apply --filename=httpd-v3.yaml --record=true
kubectl apply --filename=httpd-v1.yaml --record=true
CHANGE-CAUSE就是--record的结果,这里可以通过CHANGE-CAUSE知道每个revision的具体含义,所以执行kubect apply时加上--record参数。
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