【K8S】集群中部署nginx应用 运行手写yaml文件报错排查过程

❌报错信息

提取报错信息【 unknown field “spec.selector.replicas”】【 unknown field “spec.selector.template”】

[root@master ~]# kubectl apply -f nginx-deployment.yaml
Error from server (BadRequest): error when creating "nginx-deployment.yaml": Deployment in version "v1" cannot be handled as a Deployment: strict decoding error: unknown field "spec.selector.replicas", unknown field "spec.selector.template"
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🔎排查过程

根据报错信息，排查一下nginx-deployment YAML文件。

• 原nginx-deployment.yaml文件（编写有误）

# nginx-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata: 
  name: nginx-deploy
  namespace: default
  labels:
    chapter: first-app
spec: 
  selector: 
    matchLabels: 
      app: nginx
    replicas: 2
    template:
      metadata: 
        labels: 
          app: nginx
      spec: 
        containers: 
          - name: nginx
            image: nginx:1.7.9
            ports: 
              - containerPort: 80
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首先，使用YAML、YML在线编辑(校验)器校对一下此YAML文件格式是否正确。未发现异常。

其次，根据报错信息，定位到【unknown field “spec.selector.replicas”】【unknown field “spec.selector.template”】这两处的字段中的replicas和template这两个关键字。提示的大概意思是在spec.selector字段值里未找到这两个属性，属于未知属性。

通过运行kubectl explain deployment 查看其中字段属性位置包含关系情况。

[root@master ~]# kubectl explain deployment
KIND:     Deployment
VERSION:  apps/v1

DESCRIPTION:
     Deployment enables declarative updates for Pods and ReplicaSets.

FIELDS:
   apiVersion   <string>
     APIVersion defines the versioned schema of this representation of an
     object. Servers should convert recognized schemas to the latest internal
     value, and may reject unrecognized values. More info:
     https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources

   kind <string>
     Kind is a string value representing the REST resource this object
     represents. Servers may infer this from the endpoint the client submits
     requests to. Cannot be updated. In CamelCase. More info:
     https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds

   metadata     <Object>
     Standard object's metadata. More info:
     https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata

   spec <Object>
     Specification of the desired behavior of the Deployment.

   status       <Object>
     Most recently observed status of the Deployment.
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---

查看replicas层级关系kubectl explain deployment.spec

replicas这一字段属于spec下一级。不应该在selector这一字段的下级。

同理，template这一字段也属于spec下一级，不应该在selector这一字段的下级。

[root@master ~]# kubectl explain deployment.spec
KIND:     Deployment
VERSION:  apps/v1

RESOURCE: spec <Object>

DESCRIPTION:
     Specification of the desired behavior of the Deployment.

     DeploymentSpec is the specification of the desired behavior of the
     Deployment.

FIELDS:
   minReadySeconds      <integer>
     Minimum number of seconds for which a newly created pod should be ready
     without any of its container crashing, for it to be considered available.
     Defaults to 0 (pod will be considered available as soon as it is ready)

   paused       <boolean>
     Indicates that the deployment is paused.

   progressDeadlineSeconds      <integer>
     The maximum time in seconds for a deployment to make progress before it is
     considered to be failed. The deployment controller will continue to process
     failed deployments and a condition with a ProgressDeadlineExceeded reason
     will be surfaced in the deployment status. Note that progress will not be
     estimated during the time a deployment is paused. Defaults to 600s.

   replicas     <integer>
     Number of desired pods. This is a pointer to distinguish between explicit
     zero and not specified. Defaults to 1.

   revisionHistoryLimit <integer>
     The number of old ReplicaSets to retain to allow rollback. This is a
     pointer to distinguish between explicit zero and not specified. Defaults to
     10.

   selector     <Object> -required-
     Label selector for pods. Existing ReplicaSets whose pods are selected by
     this will be the ones affected by this deployment. It must match the pod
     template's labels.

   strategy     <Object>
     The deployment strategy to use to replace existing pods with new ones.

   template     <Object> -required-
     Template describes the pods that will be created.
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🕹️修改完成后的nginx-deployment.yaml，如下：

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deploy
  namespace: default
  labels:
    chapter: first-app
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: nginx:1.7.9
          ports:
            - containerPort: 80
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✅问题解决

重新运行该YAML文件，运行成功🎇。

[root@master ~]# kubectl apply -f nginx-deployment.yaml
deployment.apps/nginx-deploy created
[root@master ~]# kubectl get deployment
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deploy   0/2     2            0           26s
[root@master ~]# kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
nginx-deploy-7759cfdc55-q4622   1/1     Running   0          33s
nginx-deploy-7759cfdc55-skcgp   1/1     Running   0          33s
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🎇🎇🎇完结🎉🎉🎉