k8s基本概念-如何使用Services
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：
# 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
# 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：
# 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：
# 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：
# 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
# 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
# export NODE_PORT=$(kubectl get services/test-deployment-app-whoami -o go-template='{{(index .spec.ports 0).nodePort}}')
# echo NODE_PORT=$NODE_PORT
NODE_PORT=31816
# 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：
# 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
# kubectl delete services -l app=whoami
service "test-deployment-app-whoami" deleted
# 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
# 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
# kubectl apply -f whoami/app.yaml --record
deployment "app-whoami" created
service "svc-whoami" created
获取信息
# 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
# curl -s 10.96.100.22:80 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-msbmk
# curl -s tvm-00:30080 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-2pxlh
# curl -s tvm-01:30080 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-2pxlh
# curl -s tvm-02:30080 |grep Hostname
Hostname: app-whoami-6cf9cd6bf4-msbmk
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