本文使用自己利用VirtubalBox搭建的集群环境，暂时只有一个Master、一个Node。如果想了解集群的搭建，可以参考我的文章离线环境安装Kubernetes集群以及使用kubeadm安装kubernetes V1.11.1 集群。
0. 目标
在命令行下使用 kubectl 命令创建并管理部署。
1. 检查环境
检查本地的环境信息。
[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. 命令行方式创建部署
创建Tomcat部署，设置两个副本。
$ 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
创建部署之后，可以看到容器已经运行了，但是默认情况下，容器只能内部互相访问，如果需要对外提供服务，有以下几种方式：
- ClusterIP，默认的方式，通过集群IP来对外提供服务，这种方式只能在集群内部访问。
- NodePort，利用NAT技术在Node的指定端口上提供对外服务。外部应用通过:的方式访问。
- LoadBalancer，利用外部的负载均衡设施进行服务的访问。
- ExternalName，这是1.7版本之后 kube-dns 提供的功能。
2.1 端口映射，向外部暴露服务
在Kubernetes中Pod有其自己的生命周期，Node发生故障时，ReplicationController或者ReplicationSet会将Pod迁移到其他节点中以保持用户希望的状态。
[root@devops-101 ~]# kubectl expose deployment/tomcat --type="NodePort" --port 8080
service/tomcat exposed
查看service被映射到哪个端口。
[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
因为知道被调度到了102节点，手工通过浏览器打开 http://192.168.0.102:32050 检查服务是否能够正常访问。
3. 基于YAML文件创建部署
首先编辑Yaml文件
apiVersion: v1
kind: Pod
metadata: #元数据信息
name: tomcat-c #kubectl get pods 和 登陆容器显示的名字
labels: #标签，可以作为查询条件 kubectl get pods -l
app=tomcat
node=devops-103
spec: #规格
containers: #容器
- name: tomcat #容器名称
image: docker.io/tomcat #使用的镜像
ports:
- containerPort: 8080
env: #设置env，登陆到容器中查看环境变量， DEME_GREETING 的值是 "hello from the enviroment"
- name:GREETING
value: "hello from the environment"
然后创建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. 扩容部署
在扩容之前，我把devops-102节点也加入到集群中。
[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
然后再执行扩容动作。
[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. 缩容
[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. 标签功能
创建部署的时候，kubectl会自动帮我们打一个标签，这里是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
可以使用标签来查询资源，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
可以给Pods打上自定义的标签。
[root@devops-101 ~]# kubectl label --overwrite pod tomcat-858b8c476d-vnm98 node=devops-102
# 这里用了--overwrite属性是因为之前标错了
[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. 删除部署
$ kubectl delete pod-name