k8s基本概念-如何使用Services

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Services 使用示例

    Virtual IPs and service proxies
    Publishing services - service types
    通过命令行来控制 Service
    通过 yaml 配置文件来定义 Service

Virtual IPs and service proxies

    Proxy-mode: userspace
        轮询
    Proxy-mode: iptables
        v1.2开始作为默认选项
        比 userspace 快
        注意：如果一开始选择的 pod 失去响应后，不能自动重试其他 pod 因而需要定义 readiness probes
        随机
    Proxy-mode: ipvs
        FEATURE STATE: Kubernetes v1.9 beta
        比 iptables 快

Publishing services - service types

    ClusterIP
        创建一个 ClusterIP 来提供集群内部访问
        默认选项
    NodePort
        在每个节点 IP 上暴露一个端口（NodePort）来提供服务，集群外部通过这种方式来访问：<NodeIP>:<NodePort>，同时会创建一个 ClusterIP
        这种类型使用较多
        默认暴露的随机端口范围：30000-32767
        可以通过 nodePort 字段来显式的指定端口
    LoadBalancer
        通过和 cloud provider’s load balancer 关联使用，此时 NodePort and ClusterIP 将自动创建
    ExternalName
        将 service 名称映射到一个 externalName （例如一个域名），通过 kube-dns 来提供 DNS 到 CNAME 记录

通过命令行来控制 Service

    获取和创建 service


    ### 获取所有的 service 列表：
    [iyunv@tvm-00 ~]# kubectl get services
    NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
    kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   5d

创建一个网络类型为 NodePort 的 service 并暴露 pods 的 80 端口

[iyunv@tvm-00 ~]# kubectl expose deployments/test-deployment-app-whoami --type="NodePort" --port 80
service "test-deployment-app-whoami" exposed
再次获取所有的 service 列表：

[iyunv@tvm-00 ~]# kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 5d
test-deployment-app-whoami NodePort 10.108.8.154 <none> 80:31816/TCP 9s
当然，也可以通过 label 来筛选：

[iyunv@tvm-00 ~]# kubectl get services -l app=whoami
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
test-deployment-app-whoami NodePort 10.108.8.154 <none> 80:31816/TCP 23s


- 查看细节
```bash
### 查看 service 的细节：
[iyunv@tvm-00 ~]# kubectl describe services/test-deployment-app-whoami
Name:                     test-deployment-app-whoami
Namespace:                default
Labels:                   app=whoami
Annotations:              <none>
Selector:                 app=whoami
Type:                     NodePort
IP:                       10.108.8.154
Port:                     <unset>  80/TCP
TargetPort:               80/TCP
NodePort:                 <unset>  31816/TCP
Endpoints:                172.30.11.74:80,172.30.11.75:80,172.30.11.77:80 + 2 more...
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

### 此处也可以通过 label 来筛选
[iyunv@tvm-00 ~]# kubectl describe services -l app=whoami
Name:                     test-deployment-app-whoami
Namespace:                default
Labels:                   app=whoami
Annotations:              <none>
Selector:                 app=whoami
Type:                     NodePort
IP:                       10.108.8.154
Port:                     <unset>  80/TCP
TargetPort:               80/TCP
NodePort:                 <unset>  31816/TCP
Endpoints:                172.30.11.74:80,172.30.11.75:80,172.30.11.77:80 + 2 more...
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

    请求 service


    [iyunv@tvm-00 ~]# export NODE_PORT=$(kubectl get services/test-deployment-app-whoami -o go-template='{{(index .spec.ports 0).nodePort}}')
    [iyunv@tvm-00 ~]# echo NODE_PORT=$NODE_PORT
    NODE_PORT=31816

[iyunv@tvm-00 ~]# kubectl get pods -l app=whoami
NAME READY STATUS RESTARTS AGE
test-deployment-app-whoami-6cf9cd6bf4-2dd5m 1/1 Running 0 15h
test-deployment-app-whoami-6cf9cd6bf4-bb7v7 1/1 Running 0 15h
test-deployment-app-whoami-6cf9cd6bf4-c7cht 1/1 Running 0 15h
test-deployment-app-whoami-6cf9cd6bf4-jhtqz 1/1 Running 0 15h
test-deployment-app-whoami-6cf9cd6bf4-px24h 1/1 Running 0 15h
测试请求 10 次的结果：

[iyunv@tvm-00 ~]# for i in $(seq 1 10); do curl -s tvm-00:$NODE_PORT|grep Hostname; done
Hostname: test-deployment-app-whoami-6cf9cd6bf4-jhtqz
Hostname: test-deployment-app-whoami-6cf9cd6bf4-bb7v7
Hostname: test-deployment-app-whoami-6cf9cd6bf4-px24h
Hostname: test-deployment-app-whoami-6cf9cd6bf4-jhtqz
Hostname: test-deployment-app-whoami-6cf9cd6bf4-2dd5m
Hostname: test-deployment-app-whoami-6cf9cd6bf4-c7cht
Hostname: test-deployment-app-whoami-6cf9cd6bf4-c7cht
Hostname: test-deployment-app-whoami-6cf9cd6bf4-bb7v7
Hostname: test-deployment-app-whoami-6cf9cd6bf4-jhtqz
Hostname: test-deployment-app-whoami-6cf9cd6bf4-px24h
符合预期，请求随机分布在 5 个 pods 上


- 删除 service
```bash
[iyunv@tvm-00 ~]# kubectl delete services -l app=whoami
service "test-deployment-app-whoami" deleted
[iyunv@tvm-00 ~]# kubectl get services
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   5d

通过 yaml 配置文件来定义 Service

    创建配置文件


    [iyunv@tvm-00 ~]# cat ~/k8s_install/test/whoami/app.yaml
    apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
    kind: Deployment
    metadata:
    name: app-whoami
    labels:
    app: whoami
    spec:
    replicas: 3
    selector:
    matchLabels:
      app: whoami
    template:
    metadata:
      labels:
        app: whoami
    spec:
      containers:
        - name: whoami
          image: opera443399/whoami:0.9
          ports:
            - containerPort: 80

apiVersion: v1
kind: Service
metadata:
name: svc-whoami
labels:
app: whoami
spec:
selector:
app: whoami
ports:

    protocol: TCP
    port: 80
    targetPort: 80
    nodePort: 30080
    type: NodePort


- 执行
```bash
[iyunv@tvm-00 ~]# kubectl apply -f whoami/app.yaml --record
deployment "app-whoami" created
service "svc-whoami" created

    获取信息


    [iyunv@tvm-00 ~]# kubectl get all -l app=whoami
    NAME                DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
    deploy/app-whoami   3         3         3            3           25s

NAME DESIRED CURRENT READY AGE
rs/app-whoami-6cf9cd6bf4 3 3 3 25s

NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
deploy/app-whoami 3 3 3 3 25s

NAME DESIRED CURRENT READY AGE
rs/app-whoami-6cf9cd6bf4 3 3 3 25s

NAME READY STATUS RESTARTS AGE
po/app-whoami-6cf9cd6bf4-2pxlh 1/1 Running 0 25s
po/app-whoami-6cf9cd6bf4-82ng2 1/1 Running 0 25s
po/app-whoami-6cf9cd6bf4-msbmk 1/1 Running 0 25s

NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
svc/svc-whoami NodePort 10.96.100.22 <none> 80:30080/TCP 25s


- 测试
```bash
[iyunv@tvm-00 ~]# curl -s 10.96.100.22:80 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-msbmk
[iyunv@tvm-00 ~]# curl -s tvm-00:30080 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-2pxlh
[iyunv@tvm-00 ~]# curl -s tvm-01:30080 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-2pxlh
[iyunv@tvm-00 ~]# curl -s tvm-02:30080 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-msbmk