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
- 通過命令行來控制 Service
- 通過 yaml 配置文件來定義 Service
Virtual IPs and service proxies
- Proxy-mode: userspace
- 輪詢
- Proxy-mode: iptables
- v1.2開始作爲默認選項
- 比 userspace 快
- 注意：如果一開始選擇的 pod 失去響應後，不能自動重試其他 pod 因而需要定義 readiness probes
- 隨機
- Proxy-mode: ipvs
- FEATURE STATE: Kubernetes v1.9 beta
- 比 iptables 快
Publishing services - service types
- ClusterIP
- 創建一個 ClusterIP 來提供集羣內部訪問
- 默認選項
- NodePort
- 在每個節點 IP 上暴露一個端口（NodePort）來提供服務，集羣外部通過這種方式來訪問：<NodeIP>:<NodePort>，同時會創建一個 ClusterIP
- 這種類型使用較多
- 默認暴露的隨機端口範圍：30000-32767
- 可以通過 nodePort 字段來顯式的指定端口
- LoadBalancer
- 通過和 cloud provider’s load balancer 關聯使用，此時 NodePort and ClusterIP 將自動創建
- ExternalName
- 將 service 名稱映射到一個 externalName （例如一個域名），通過 kube-dns 來提供 DNS 到 CNAME 記錄
通過命令行來控制 Service
- 獲取和創建 service
### 獲取所有的 service 列表： [root@tvm-00 ~]# kubectl get services NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 5d
創建一個網絡類型爲 NodePort 的 service 並暴露 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
再次獲取所有的 service 列表：
[root@tvm-00 ~]# kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 5d
test-deployment-app-whoami NodePort 10.108.8.154 <none> 80:31816/TCP 9s
當然，也可以通過 label 來篩選：
[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 <none> 80:31816/TCP 23s
- 查看細節
```bash
### 查看 service 的細節：
[root@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>
### 此處也可以通過 label 來篩選
[root@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>- 請求 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
測試請求 10 次的結果：
[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
符合預期，請求隨機分佈在 5 個 pods 上
- 刪除 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 <none> 443/TCP 5d通過 yaml 配置文件來定義 Service
- 創建配置文件
[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
- 執行
```bash
[root@tvm-00 ~]# kubectl apply -f whoami/app.yaml --record
deployment "app-whoami" created
service "svc-whoami" created- 獲取信息
[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 <none> 80:30080/TCP 25s
- 測試
```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