k8s之Headless Service
1. Headless Service
see: Headless services
headless service 需要将 spec.clusterIP 设置成 None。
因为没有ClusterIP，kube-proxy 并不处理此类服务，因为没有load balancing或 proxy 代理设置，在访问服务的时候回返回后端的全部的Pods IP地址，主要用于开发者自己根据pods进行负载均衡器的开发(设置了selector)。
2. Test Headless Service With selectors
| $cat deployment.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx-deployment
spec:
replicas: 2 # tells deployment to run 2 pods matching the template
template: # create pods using pod definition in this template
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metadata:
# unlike pod-nginx.yaml, the name is not included in the meta data as a unique name is
# generated from the deployment name
labels:
app: nginx_test
spec:
containers:
- name: nginx
image: nginx:1.7.9
ports:
- containerPort: 80
|
| $ cat headless_service.yaml
kind: Service
apiVersion: v1
metadata:
name: nginx-service
spec:
selector:
app: nginx_test
ports:
- protocol: TCP
port: 80
targetPort: 80
clusterIP: None
|
通过dns访问，会返回后端pods的列表
登录到Cluster的内部pod
| nslookup nginx-service
nslookup: can't resolve '(null)': Name does not resolve
Name: nginx-service
Address 1: 10.10.23.36
Address 2: 10.10.23.39
|