K8S对node添加label，并根据label筛选节点

某些特殊情况下，需要将某些服务固定在一台宿主机上，K8S也适应这种方式，下面以mongo为例，来看看如何实现的：

kubectl label nodes kube-node node=kube-node

kubectl get node -a -l "node=kube-node"

nodeSelector:
node: kube-node4

apiVersion: v1
kind: ReplicationController
metadata:
name: mongo
spec:
replicas: 1
template:
metadata:
labels:
run: mongo
spec:
containers:
- name: mongo
image: daocloud.io/library/mongo:3.2.4
ports:
- containerPort: 27017
volumeMounts:
- mountPath: /data/db
name: mongo
volumes: [{"name":"mongo","hostPath":{"path":"/root/volumes/mongo"}}]
nodeSelector:
node: kube-node4