Deployments是在Kubernetes 1.2版本增加的特性，作为对于pod的控制，Deployments实现了声明式的应用发布和升级，保证了应用的高可用性和快速回滚的能力。在Kubernetes 1.8时相关API移至apps/v1beta2，在Kubernetes 1.9中整合至apps/v1，随着环境中的Kubernetes的升级，原有API的废弃导致Deployment的相应yaml文件需要修改，这篇文章以旧版的Prometheus的Deployment的修改为例，介绍Deployments修改需要注意的事项。

事前准备

本文示例中准备了Kubernetes 1.17的环境，环境的准备方法可参考如下Easyapck下的Ansible一键脚本。

单机版本或者集群版本环境搭建

[root@host131 ansible]# kubectl version
Client Version: version.Info{Major:"1", Minor:"17", GitVersion:"v1.17.0", GitCommit:"70132b0f130acc0bed193d9ba59dd186f0e634cf", GitTreeState:"clean", BuildDate:"2019-12-07T21:20:10Z", GoVersion:"go1.13.4", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"17", GitVersion:"v1.17.0", GitCommit:"70132b0f130acc0bed193d9ba59dd186f0e634cf", GitTreeState:"clean", BuildDate:"2019-12-07T21:12:17Z", GoVersion:"go1.13.4", Compiler:"gc", Platform:"linux/amd64"}
[root@host131 ansible]#
[root@host131 ansible]# kubectl get nodes -o wide
NAME              STATUS   ROLES    AGE   VERSION   INTERNAL-IP       EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION          CONTAINER-RUNTIME
192.168.163.131   Ready    <none>   18m   v1.17.0   192.168.163.131   <none>        CentOS Linux 7 (Core)   3.10.0-957.el7.x86_64   docker://18.9.7
[root@host131 ansible]#

Deployment示例准备

如下是Deployment在beta1阶段的Yaml文件示例

[root@host131 prometheus]# cat prometheus-deployment.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:name: prometheus-deploymentnamespace: monitoring
spec:replicas: 1template:metadata:labels:app: prometheus-serverspec:containers:- name: prometheusimage: prom/prometheus:v2.12.0args:- "--config.file=/etc/prometheus/prometheus.yml"- "--storage.tsdb.path=/prometheus/"ports:- containerPort: 9090volumeMounts:- name: prometheus-config-volumemountPath: /etc/prometheus/- name: prometheus-storage-volumemountPath: /prometheus/volumes:- name: prometheus-config-volumeconfigMap:defaultMode: 420name: prometheus-server-conf- name: prometheus-storage-volumeemptyDir: {}
[root@host131 prometheus]#

Yaml文件中所需要的命名空间ConfigMap等其他准备也事前已经准备：

[root@host131 prometheus]# kubectl get ns |grep monitoring
monitoring        Active   3m18s
[root@host131 prometheus]# kubectl get clusterrole |grep prometheus
prometheus                                                             3m1s
[root@host131 prometheus]# kubectl get clusterrolebindings |grep prometheus
prometheus                                             3m7s
[root@host131 prometheus]# kubectl get cm -n monitoring
NAME                     DATA   AGE
prometheus-server-conf   2      93s
[root@host131 prometheus]#

API变化所需要的对应事项

从上述extensions/v1beta1到apps/v1，Deployment需要进行如下修改：

对应事项1: 修改apiVersion

在Kubernetes 1.17下直接使用使用上述Yaml文件进行Deployment的创建，首先会提示如下错误信息：

[root@host131 prometheus]# kubectl create -f prometheus-deployment.yaml
error: unable to recognize "prometheus-deployment.yaml": no matches for kind "Deployment" in version "extensions/v1beta1"
[root@host131 prometheus]#

原因很简单，在这个版本中，extensions/v1beta1中已经没有Deployment了，已经被移除了，只能使用apps/v1了，然后做如下修改

[root@host131 prometheus]# cp prometheus-deployment.yaml prometheus-deployment.yaml.org
[root@host131 prometheus]# vi prometheus-deployment.yaml
[root@host131 prometheus]# diff prometheus-deployment.yaml prometheus-deployment.yaml.org
1c1
< apiVersion: apps/v1
---
> apiVersion: extensions/v1beta1
[root@host131 prometheus]#

对应事项2: Deployment.spec中添加selector

修改apiVersion之后，再次执行kubectl create命令进行Deployment的创建，会得到如下错误信息提示：

[root@host131 prometheus]# kubectl create -f prometheus-deployment.yaml
error: error validating "prometheus-deployment.yaml": error validating data: ValidationError(Deployment.spec): missing required field "selector" in io.k8s.api.apps.v1.DeploymentSpec; if you choose to ignore these errors, turn validation off with --validate=false
[root@host131 prometheus]#

原因也非常清晰，Deployment.spec中需要添加selector选择器，使用Kubernetes自带的帮助文档进行确认Deployment.spec.selector的写法

[root@host131 prometheus]# kubectl explain Deployment.spec.selector
KIND:     Deployment
VERSION:  apps/v1RESOURCE: selector <Object>DESCRIPTION:Label selector for pods. Existing ReplicaSets whose pods are selected bythis will be the ones affected by this deployment. It must match the podtemplate's labels.A label selector is a label query over a set of resources. The result ofmatchLabels and matchExpressions are ANDed. An empty label selector matchesall objects. A null label selector matches no objects.FIELDS:matchExpressions   <[]Object>matchExpressions is a list of label selector requirements. The requirementsare ANDed.matchLabels    <map[string]string>matchLabels is a map of {key,value} pairs. A single {key,value} in thematchLabels map is equivalent to an element of matchExpressions, whose keyfield is "key", the operator is "In", and the values array contains only"value". The requirements are ANDed.[root@host131 prometheus]#

对配置文件进行如下修改

[root@host131 prometheus]# vi prometheus-deployment.yaml
[root@host131 prometheus]# diff prometheus-deployment.yaml prometheus-deployment.yaml.org
1c1
< apiVersion: apps/v1
---
> apiVersion: extensions/v1beta1
8,10d7
<   selector:
<     matchLabels:
<       app: prometheus-server
[root@host131 prometheus]# cat prometheus-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:name: prometheus-deploymentnamespace: monitoring
spec:replicas: 1selector:matchLabels:app: prometheus-servertemplate:metadata:labels:app: prometheus-serverspec:containers:- name: prometheusimage: prom/prometheus:v2.12.0args:- "--config.file=/etc/prometheus/prometheus.yml"- "--storage.tsdb.path=/prometheus/"ports:- containerPort: 9090volumeMounts:- name: prometheus-config-volumemountPath: /etc/prometheus/- name: prometheus-storage-volumemountPath: /prometheus/volumes:- name: prometheus-config-volumeconfigMap:defaultMode: 420name: prometheus-server-conf- name: prometheus-storage-volumeemptyDir: {}
[root@host131 prometheus]#

既然是matchLabels，当然就需要设定相应的Label，这里添加了Deployment.spec.selector，实际上此Label需要和template里面的Label一致，这里之所以定义为app: prometheus-server也是因为为了和template已经存在的Label保持一致，这样就可以成功的进行创建了

[root@host131 prometheus]# kubectl create -f prometheus-deployment.yaml
deployment.apps/prometheus-deployment created
[root@host131 prometheus]# kubectl get pods -n monitoring
NAME                                     READY   STATUS    RESTARTS   AGE
prometheus-deployment-5c4f4f5779-vvr6h   1/1     Running   0          9m17s
[root@host131 prometheus]# kubectl get deployment -n monitoring
NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
prometheus-deployment   1/1     1            1           13m
[root@host131 prometheus]#

如果两者不一致的情况下，也会提示错误信息，比如这里我们特意将Label改成不一致

[root@host131 prometheus]# kubectl delete -f prometheus-deployment.yaml
deployment.apps "prometheus-deployment" deleted
[root@host131 prometheus]# cp prometheus-deployment.yaml prometheus-deployment.yaml.test
[root@host131 prometheus]# vi prometheus-deployment.yaml.test
[root@host131 prometheus]# diff prometheus-deployment.yaml prometheus-deployment.yaml.test
10c10
<       app: prometheus-server
---
>       app: prometheus-test
[root@host131 prometheus]#

不一致的情况下就会明确的提示，Deployment的selector和spec.template.metadata.labels不一致。

[root@host131 prometheus]# kubectl create -f prometheus-deployment.yaml.test
The Deployment "prometheus-deployment" is invalid: spec.template.metadata.labels: Invalid value: map[string]string{"app":"prometheus-server"}: `selector` does not match template `labels`
[root@host131 prometheus]#

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