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Kubernetes resource object introduction and common commands (III)

2022-07-03 17:11:00 【Silly [email protected]】

Service

A set of Pods An abstract method that is exposed as a network service . It can also be understood as Pod Service discovery and load balancing .

Service discovery and load balancing ：Service Will detect pod The state of , Traffic will only be sent to normal with average scores pod in .

establish Service

expose Deploy. port 8000.

Command line mode

[[email protected] ~]# kubectl expose deployment my-app --port=8000 --target-port=80
service/my-app exposed
[[email protected] ~]# kubectl get service

yaml The way ,service.yml

apiVersion: v1
kind: Service
metadata:
  labels:
    app: my-app
  name: my-app
spec:
  selector:
    app: my-app
  ports:
  - port: 8000
    protocol: TCP
    targetPort: 80

[[email protected] ~]# kubectl apply -f service.yml 
service/my-app created
[[email protected] ~]#

see Service

[[email protected] ~]# kubectl get service -n default
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)    AGE
kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP    23h
my-app       ClusterIP   10.96.2.98   <none>        8000/TCP   6s
[[email protected] ~]#

You can see what we created above Service Of ip by 10.96.2.98.

[[email protected] ~]# curl 10.96.2.98:8000
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
    
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
...
</html>
[[email protected] ~]#

Be careful ： We can use ip:8000 In the form of any node access in the cluster . We can also do that pod Inside Use domain name : port Form access . The form of domain name ：service name . Namespace .svc: port . for example ：my-app.default.svc:8000.

Expand ：

see pod label

[[email protected] ~]# kubectl get pod [podname] --show-labels
NAME                      READY   STATUS    RESTARTS   AGE   LABELS
my-app-5ff664f457-l7792   1/1     Running   1          20h   app=my-app,pod-template-hash=5ff664f457
my-app-5ff664f457-r69z5   1/1     Running   1          20h   app=my-app,pod-template-hash=5ff664f457
my-app-5ff664f457-w2d6q   1/1     Running   1          20h   app=my-app,pod-template-hash=5ff664f457
my-app-5ff664f457-xsz9l   1/1     Running   1          20h   app=my-app,pod-template-hash=5ff664f457
[[email protected] ~]#

Use tags to retrieve Pod

[[email protected] ~]# kubectl get pod -l app=my-app
NAME                      READY   STATUS    RESTARTS   AGE
my-app-5ff664f457-l7792   1/1     Running   1          20h
my-app-5ff664f457-r69z5   1/1     Running   1          20h
my-app-5ff664f457-w2d6q   1/1     Running   1          20h
my-app-5ff664f457-xsz9l   1/1     Running   1          20h
[[email protected] ~]#

Delete Service

[[email protected] ~]# kubectl delete service my-app
service "my-app" deleted
[[email protected] ~]#

ClusterIP

We created Service The default is ClusterIP, It's called clustering ip, It can only be used inside the cluster . Equate to :

kubectl expose deployment my-app --port=8000 --target-port=80 --type=ClusterIP

apiVersion: v1
kind: Service
metadata:
  labels:
    app: my-app
  name: my-app
spec:
  ports:
  - port: 8000
    protocol: TCP
    targetPort: 80
  selector:
    app: my-app
  type: ClusterIP

NodePort

Created this way Service It can also be accessed outside the cluster . Because he will be in every pod Show a new port .

Command line mode

[[email protected] ~]# kubectl expose deploy my-app --port=8000 --target-port=80 --type=NodePort
service/my-app exposed
[[email protected] ~]#

yaml The way .service.yml

apiVersion: v1
kind: Service
metadata:
  labels:
    app: my-app
  name: my-app
spec:
  ports:
  - port: 8000
    protocol: TCP
    targetPort: 80
  selector:
    app: my-app
  type: NodePort

kubectl apply -f service.yml

[[email protected] ~]# kubectl get svc
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP          25h
my-app       NodePort    10.96.198.191   <none>        8000:32047/TCP   39s
[[email protected] ~]#

Contrast found in PORT(S) A mapping port is added in 32047, This port is available on every node , Can pass node ip:30247 Access outside the cluster .

NodePort In addition to being accessible outside the cluster , The rest and ClusterIP Agreement .

Summary

NodePort The scope is 30000-32767 Randomly generated between .
ClusterIP Can only be used within a cluster .
NodePort Can pass node ip: new port Access outside the cluster .
Whether it's ClusterIP still NodePort, Will generate CLUSTER-IP, It can be used in the cluster .
Use ip: port To use on cluster nodes , and domain name : port To be in pod Internal use .
How to write a domain name ： service name . In the namespace .svc

This paper is written by mdnice Multi platform Publishing

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