Kubernetes - services without selector

问题

I'm struggling with Kubernetes' service without a selector. The cluster is installed on AWS with the kops. I have a deployment with 3 nginx pods exposing port 80:

apiVersion: apps/v1
kind: Deployment
metadata:
 name: ngix-dpl                 # Name of the deployment object
 labels:
   app: nginx                     
spec:
 replicas: 3                    # Number of instances in the deployment
 selector:                      # Selector identifies pods to be
     matchLabels:               #     part of the deployment 
        app: nginx              #     by matching of the label "app" 
 template:                      # Templates describes pods of the deployment
   metadata:
     labels:                    # Defines key-value map
       app: nginx               # Label to be recognized by other objects
   spec:                        #     as deployment or service
     containers:                # Lists all containers in the pod
     - name: nginx-pod          # container name
       image: nginx:1.17.4      # container docker image
       ports:
       - containerPort: 80      # port exposed by container

After creation of the deployment, I noted the IP addresses:

$ kubectl get pods -o wide | awk {'print $1" " $3" " $6'} | column -t
                                                                           NAME                       STATUS   IP
curl                       Running  100.96.6.40
ngix-dpl-7d6b8c8944-8zsgk  Running  100.96.8.53
ngix-dpl-7d6b8c8944-l4gwk  Running  100.96.6.43
ngix-dpl-7d6b8c8944-pffsg  Running  100.96.8.54

and created a service that should serve the IP addresses:

apiVersion: v1
kind: Service
metadata:
  name: dummy-svc
  labels:
    app: nginx
spec:
 ports:
    - protocol: TCP
      port: 80
      targetPort: 80
---
apiVersion: v1
kind: Endpoints
metadata:
  name: dummy-svc 
subsets: 
  - addresses:
    - ip: 100.96.8.53
    - ip: 100.96.6.43
    - ip: 100.96.8.54
    ports:
    - port: 80
      name: http

The service is successfully created:

$ kubectl get svc
NAME         TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
dummy-svc    ClusterIP   100.64.222.220   <none>        80/TCP    32m
kubernetes   ClusterIP   100.64.0.1       <none>        443/TCP   5d14h

Unfortunately, my attempt to connect to the nginx through the service from another pod of the same namespace fails:

$ curl 100.64.222.220
curl: (7) Failed to connect to 100.64.222.220 port 80: Connection refused

I can successfully connect to the nginx pods directly:

$ curl 100.96.8.53
<!DOCTYPE html>
<html>
<head>
....

I noticed that my service does not have any endpoints. But I'm not sure that the manual endpoints should be shown there:

$ kubectl get svc/dummy-svc -o yaml
apiVersion: v1
kind: Service
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |      
       {"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"labels":{"app":"nginx"},"name":"dummy-svc","namespace":"default"},"spec":{"ports":[{"port":80,"protocol":"TCP","targetPort":80}]}}
  creationTimestamp: "2019-11-22T08:41:29Z"
  labels:
    app: nginx
  name: dummy-svc
  namespace: default
  resourceVersion: "4406151"
  selfLink: /api/v1/namespaces/default/services/dummy-svc
  uid: e0aa9d01-0d03-11ea-a19c-0a7942f17bf8
spec:
  clusterIP: 100.64.222.220
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  sessionAffinity: None
  type: ClusterIP
status:
  loadBalancer: {}

I understand that it is not a proper use case for services and using of a pod selector will bring it to work. But I want to understend why this configuration does not work. I don't know where to look for the solution. Any hint will be appreciated.

回答1:

it works if you remove the "name" field from the endpoints configuration. it should look like this:

apiVersion: v1
kind: Endpoints
metadata:
  name: dummy-svc 
subsets: 
  - addresses:
    - ip: 172.17.0.4
    - ip: 172.17.0.5
    - ip: 172.17.0.6
    ports:
    - port: 80

回答2:

correct the service definition as below

apiVersion: v1
kind: Service
metadata:
  name: dummy-svc
  labels:
    app: nginx
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80
  selector:
   app: nginx

来源：https://stackoverflow.com/questions/58991516/kubernetes-services-without-selector

标签

amazon-web-services

Docker

nginx

Kubernetes

kops