k8s基本概念-如何使用Services
2018/1/5
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：
: ，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
- 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：
- 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： [root@tvm-00 ~]# kubectl get services NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1443/TCP 5d
创建一个网络类型为 NodePort 的 service 并暴露 pods 的 80 端口
[root@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：
[root@tvm-00 ~]# kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1
test-deployment-app-whoami NodePort 10.108.8.154
当然，也可以通过 label 来筛选：
[root@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
- 查看细节
```bash
### 查看 service 的细节：
[root@tvm-00 ~]# kubectl describe services/test-deployment-app-whoami
Name: test-deployment-app-whoami
Namespace: default
Labels: app=whoami
Annotations:
Selector: app=whoami
Type: NodePort
IP: 10.108.8.154
Port: 80/TCP
TargetPort: 80/TCP
NodePort: 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:
### 此处也可以通过 label 来筛选
[root@tvm-00 ~]# kubectl describe services -l app=whoami
Name: test-deployment-app-whoami
Namespace: default
Labels: app=whoami
Annotations:
Selector: app=whoami
Type: NodePort
IP: 10.108.8.154
Port: 80/TCP
TargetPort: 80/TCP
NodePort: 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: - 请求 service
[root@tvm-00 ~]# export NODE_PORT=$(kubectl get services/test-deployment-app-whoami -o go-template='{{(index .spec.ports 0).nodePort}}') [root@tvm-00 ~]# echo NODE_PORT=$NODE_PORT NODE_PORT=31816
[root@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：
[root@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
[root@tvm-00 ~]# kubectl delete services -l app=whoami
service "test-deployment-app-whoami" deleted
[root@tvm-00 ~]# kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 443/TCP 5d 通过 yaml 配置文件来定义 Service
- 创建配置文件
[root@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
[root@tvm-00 ~]# kubectl apply -f whoami/app.yaml --record
deployment "app-whoami" created
service "svc-whoami" created- 获取信息
[root@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
- 测试
```bash
[root@tvm-00 ~]# curl -s 10.96.100.22:80 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-msbmk
[root@tvm-00 ~]# curl -s tvm-00:30080 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-2pxlh
[root@tvm-00 ~]# curl -s tvm-01:30080 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-2pxlh
[root@tvm-00 ~]# curl -s tvm-02:30080 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-msbmk