使用kubectl創建部署

本文使用自己利用VirtubalBox搭建的集群環境，暫時只有一個Master、一個Node。如果想了解集群的搭建，可以參考我的文章離線環境安裝Kubernetes集群以及使用kubeadm安裝kubernetes V1.11.1 集群。

0. 目標

在命令行下使用 kubectl 命令創建並管理部署。

1. 檢查環境

檢查本地的環境信息。

[root@devops-101 ~]# kubectl get nodes
NAME         STATUS     ROLES     AGE       VERSION
devops-101   Ready      master    7h        v1.11.1
devops-102   Ready      <none>    6h        v1.11.1

2. 命令行方式創建部署

創建Tomcat部署，設置兩個副本。

$ kubectl run docker.io/tomcat --replicas=2 --labels="app=tomcat" --image=docker.io/tomcat --port=8080
deployment.apps/tomcat created
[root@devops-101 ~]# kubectl get deployment
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
tomcat    2         2         2            2           6m
[root@devops-101 ~]# kubectl get pods
NAME                      READY     STATUS    RESTARTS   AGE
tomcat-858b8c476d-vnm98   1/1       Running   0          6m
tomcat-858b8c476d-xl5xl   1/1       Running   0          6m

創建部署之后，可以看到容器已經運行了，但是默認情況下，容器只能內部互相訪問，如果需要對外提供服務，有以下幾種方式：

• ClusterIP，默認的方式，通過集群IP來對外提供服務，這種方式只能在集群內部訪問。
• NodePort，利用NAT技術在Node的指定端口上提供對外服務。外部應用通過 : 的方式訪問。
• LoadBalancer，利用外部的負載均衡設施進行服務的訪問。
• ExternalName，這是1.7版本之后 kube-dns 提供的功能。

2.1 端口映射，向外部暴露服務

在Kubernetes中Pod有其自己的生命周期，Node發生故障時，ReplicationController或者ReplicationSet會將Pod遷移到其他節點中以保持用戶希望的狀態。

[root@devops-101 ~]# kubectl expose deployment/tomcat --type="NodePort" --port 8080
service/tomcat exposed

查看service被映射到哪個端口。

[root@devops-101 ~]# kubectl get service
NAME         TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)          AGE
kubernetes   ClusterIP   10.96.0.1      <none>        443/TCP          8h
tomcat       NodePort    10.98.152.28   <none>        8080:32050/TCP   7s

因為知道被調度到了102節點，手工通過瀏覽器打開 http://192.168.0.102:32050 檢查服務是否能夠正常訪問。

3. 基於YAML文件創建部署

首先編輯Yaml文件

apiVersion: v1
kind: Pod
metadata:                           #元數據信息
  name: tomcat-c                    #kubectl get  pods 和 登陸容器顯示的名字
  labels:                           #標簽，可以作為查詢條件 kubectl get pods -l
    app=tomcat
    node=devops-103
spec:　　　　　　　　　　　　　　　 #規格
  containers:                       #容器
  - name: tomcat                    #容器名稱
    image: docker.io/tomcat         #使用的鏡像
    ports:
      - containerPort: 8080
    env:　　　　　　　　　　　　　　#設置env，登陸到容器中查看環境變量， DEME_GREETING 的值是 "hello from the enviroment"
    - name:GREETING
      value: "hello from the environment"

然后創建Pod。

[root@devops-101 ~]# kubectl create -f tomcat.yaml 
pod/tomcat-ccb created
[root@devops-101 ~]# kubectl get pods
NAME                      READY     STATUS    RESTARTS   AGE
tomcat-858b8c476d-vnm98   1/1       Running   2          21h
tomcat-858b8c476d-xl5xl   1/1       Running   3          21h
tomcat-ccb                1/1       Running   0          34s

4. 擴容部署

在擴容之前，我把devops-102節點也加入到集群中。

[root@devops-101 ~]# kubectl get nodes
NAME         STATUS    ROLES     AGE       VERSION
devops-101   Ready     master    9h        v1.11.1
devops-102   Ready     <none>    8h        v1.11.1
devops-103   Ready     <none>    7h        v1.11.1

然后再執行擴容動作。

[root@devops-101 ~]# kubectl scale deployments/tomcat --replicas=3
deployment.extensions/tomcat scaled
[root@devops-101 ~]# kubectl get deployments
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
tomcat    3         3         3            2           1h
[root@devops-101 ~]# kubectl get pods
NAME                      READY     STATUS              RESTARTS   AGE
tomcat-858b8c476d-cfrtt   0/1       ContainerCreating   0          2m
tomcat-858b8c476d-vnm98   1/1       Running             0          1h
tomcat-858b8c476d-xl5xl   1/1       Running             0          1h
[root@devops-101 ~]# kubectl describe pod tomcat-858b8c476d-cfrtt
Name:           tomcat-858b8c476d-cfrtt
Namespace:      default
Node:           devops-103/192.168.0.103
Start Time:     Tue, 24 Jul 2018 18:29:51 +0800
Labels:         app=tomcat
                pod-template-hash=4146470328
Annotations:    <none>
Status:         Pending
IP:             
Controlled By:  ReplicaSet/tomcat-858b8c476d
Containers:
  tomcat:
    Container ID:   
    Image:          docker.io/tomcat
    Image ID:       
    Port:           8080/TCP
    Host Port:      0/TCP
    State:          Waiting
      Reason:       ContainerCreating
    Ready:          False
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-trvqv (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             False 
  ContainersReady   False 
  PodScheduled      True 
Volumes:
  default-token-trvqv:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-trvqv
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age        From                 Message
  ----    ------     ----       ----                 -------
  Normal  Scheduled  2m         default-scheduler    Successfully assigned default/tomcat-858b8c476d-cfrtt to devops-103
  Normal  Pulling    <invalid>  kubelet, devops-103  pulling image "docker.io/tomcat"

5. 縮容

[root@devops-101 ~]# kubectl scale deployments/tomcat --replicas=2
deployment.extensions/tomcat scaled
[root@devops-101 ~]# kubectl get pods
NAME                      READY     STATUS    RESTARTS   AGE
tomcat-858b8c476d-vnm98   1/1       Running   0          1h
tomcat-858b8c476d-xl5xl   1/1       Running   0          1h

6. 標簽功能

創建部署的時候，kubectl會自動幫我們打一個標簽，這里是app=tomcat。

[root@devops-101 ~]# kubectl describe deployment
Name:                   tomcat
Namespace:              default
CreationTimestamp:      Tue, 24 Jul 2018 16:35:08 +0800
Labels:                 app=tomcat
Annotations:            deployment.kubernetes.io/revision=1
Selector:               app=tomcat
Replicas:               2 desired | 2 updated | 2 total | 2 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=tomcat
  Containers:
   tomcat:
    Image:        docker.io/tomcat
    Port:         8080/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Progressing    True    NewReplicaSetAvailable
  Available      True    MinimumReplicasAvailable
OldReplicaSets:  <none>
NewReplicaSet:   tomcat-858b8c476d (2/2 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  18m   deployment-controller  Scaled up replica set tomcat-858b8c476d to 3
  Normal  ScalingReplicaSet  4m    deployment-controller  Scaled down replica set tomcat-858b8c476d to 2

可以使用標簽來查詢資源，包括Pods和Services。

[root@devops-101 ~]# kubectl get pods -l app=tomcat
NAME                      READY     STATUS    RESTARTS   AGE
tomcat-858b8c476d-vnm98   1/1       Running   0          1h
tomcat-858b8c476d-xl5xl   1/1       Running   0          1h
[root@devops-101 ~]# kubectl get services -l app=tomcat
NAME      TYPE       CLUSTER-IP     EXTERNAL-IP   PORT(S)          AGE
tomcat    NodePort   10.98.152.28   <none>        8080:32050/TCP   1h

可以給Pods打上自定義的標簽。

[root@devops-101 ~]# kubectl label --overwrite  pod tomcat-858b8c476d-vnm98 node=devops-102
# 這里用了--overwrite屬性是因為之前標錯了
[root@devops-101 ~]# kubectl describe pods tomcat-858b8c476d-vnm98
Name:           tomcat-858b8c476d-vnm98
Namespace:      default
Node:           devops-102/192.168.0.102
Start Time:     Tue, 24 Jul 2018 16:35:08 +0800
Labels:         app=tomcat
                node=devops-102
                pod-template-hash=4146470328
Annotations:    <none>
Status:         Running
IP:             10.244.2.6
Controlled By:  ReplicaSet/tomcat-858b8c476d
Containers:
  tomcat:
    Container ID:   docker://9f3aa2d3d6c1937d4209a44820c1cd06f7eaf8796848c759e19410358aea4866
    Image:          docker.io/tomcat
    Image ID:       docker-pullable://docker.io/tomcat@sha256:87ad70ceaafd5c71301b081b37ca2795bd6c7c1a5599a8c92c9447bbd225ae47
    Port:           8080/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Tue, 24 Jul 2018 16:35:37 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-trvqv (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-trvqv:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-trvqv
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:          <none>

7. 刪除部署

$ kubectl delete pod-name

參考資料

1. Using kubectl to Create a Deployment
2. kubernetes 安裝學習
3. kubernetes step by step