kubernetes-- scheduling constraints

Fundamental

kubernetes通过watch的机制进行每个组件的协作，每个组件之间的设计实现了解耦.

Scheduling

nodeName用于将Pod调度到指定的Node名称上,跳过调度器直接分配.

nodeSelector用于将Pod调度到匹配Label的Node上,前提是node要有标签.

Detailed principles

图中左上角的运维人员往节点中创建一个nginx资源.

API Server和etcd和Scheduler是master.

Kubelet和Docker是node节点.

API Server做为唯一入口，接受create创建资源的属性信息写入到etcd中（属性信息：名称，镜像名称，限制条件），
etcd完善发现机制（watch）给Scheduler调度器（查看那个节点适合），然后绑定相关pod的网络信息，
反馈给API Server，收到信息后api写入etcd中，此时etcd存储了pod的网络信息（IP），node1、中的kubelet会管理pod资源，
会触发容器的创建命令，安装完成后docker就会反馈状态信息给API Server，当API Server收到状态信息写入到etcd中.

API Server相当于是平台中的管理员,负责记录相关信息,

etcd相当于管理员的记事本,相关信息内容写在其中,

如果API Server挂了，那么k8s基本上就瘫痪了.

Sample demonstrates -nodeName

• Edit the file yaml

vim pod5.yaml

apiVersion: v1
kind: Pod
metadata:
  name: pod-example
  labels:
    app: nginx
spec:
  nodeName: 192.168.142.131
  #指定给node1节点
  containers:
  - name: nginx
    image: nginx:1.15
    #验证是否创建了nginx

• Create a file yaml

kubectl create -f pod5.yaml

kubectl get pods

• View detailed event scheduler has not been found

kubectl describe pod pod-example

• Empty pod resources

kubectl delete -f .

kubectl get pods

Sample demonstrates -nodeSelector

• Gets the label Help

kubectl label --help

• NAME need to get the name of the node

kubectl get node

• Provided to the corresponding node label kgc = a and, respectively kgc = b

kubectl label nodes 192.168.142.130 kgc=a

kubectl label nodes 192.168.142.131 kgc=b

• Look at the label

kubectl get nodes --show-labels

vim pod5.yaml

apiVersion: v1
kind: Pod
metadata:
  name: pod-example
  labels:
    app: nginx
spec:
  nodeSelector: 
    kgc: b
  containers:
  - name: nginx
    image: nginx:1.15

kubectl apply -f pod5.yaml

• View event details can be observed through the scheduler allocates by events

kubectl describe pod pod-example

Troubleshooting

• View pod event

kubectl describe TYPE NAME_PREFIX

• View Log pod (under Failed state)

kubectl logs POD_NAME

• Into the pod (status is running, but the service is not provided)

kubectl exec –it POD_NAME bash

thanks for reading!