Cannot access standalone-chrome selenium server via Kubernetes service-CodePudding

I have a k0s Kubernetes cluster on a single node. I am trying to run a selenium/standalone-chrome to create a remote Selenium node. The trouble that I am having is that it responds if I port forward 4444 from the pod, but cannot seem to access it via a Service port. I get connection refused. I don't know if it's because it's ignore connections that non-localhost.

The Pod definition for pod/standalone-chrome is:

apiVersion: v1
kind: Pod
metadata:
  name: standalone-chrome
spec:
  containers:
  - name: standalone-chrome
    image: selenium/standalone-chrome
    ports:
    - containerPort: 4444
    env:
    - name: JAVA_OPTS
      value: '-Dwebdriver.chrome.whitelistedIps=""'

The Service definition I have for service/standalone-chrome-service is:

apiVersion: v1
kind: Service
metadata:
  name: standalone-chrome-service
  labels:
    app: standalone-chrome
spec:
  ports:
  - port: 4444
    name: standalone-chrome
  type: ClusterIP
  selector:
    app: standalone-chrome

This creates the following, along with a busybox container I have just for testing connectivity.

NAME                         READY   STATUS    RESTARTS   AGE
pod/busybox1                 1/1     Running   70         2d22h
pod/standalone-chrome        1/1     Running   0          3m15s

NAME                                TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
service/kubernetes                  ClusterIP   10.96.0.1       <none>        443/TCP          18d
service/standalone-chrome-service   ClusterIP   10.111.12.1     <none>        4444/TCP         3m5s

The issue I am having now is that I'm not able to access the remote Selenium service via standalone-chrome-service. I get connection refused. For example, here is trying to reach it via the busybox1 container:

$ wget http://standalone-chrome-service:4444
Connecting to standalone-chrome-service:4444 (10.111.12.1:4444)
wget: can't connect to remote host (10.111.12.1): Connection refused

I am able to port forward from pod/standalone-chrome to my host machine using kubectl port-forward though and it works OK, which I think confirms a service is successfully running but not accessible via the Service:

$ kubectl port-forward pod/standalone-chrome 4444:4444 &
Forwarding from 127.0.0.1:4444 -> 4444
Forwarding from [::1]:4444 -> 4444
$ wget http://localhost:4444
--2021-11-22 13:37:20--  http://localhost:4444/
Resolving localhost (localhost)... ::1, 127.0.0.1
Connecting to localhost (localhost)|::1|:4444... connected.
...

I'd greatly appreciate any help in figuring out how to get the Selenium remote server accessible via the Service.

EDIT: Here is the updated Service definition with name...

apiVersion: v1
kind: Service
metadata:
  name: standalone-chrome-service
  labels:
    app: standalone-chrome
spec:
  ports:
  - port: 4444
    name: standalone-chrome
  type: ClusterIP
  selector:
    name: standalone-chrome

Here is the output of describe:

Name:              standalone-chrome-service
Namespace:         default
Labels:            app=standalone-chrome
Annotations:       <none>
Selector:          name=standalone-chrome
Type:              ClusterIP
IP Families:       <none>
IP:                10.100.179.116
IPs:               10.100.179.116
Port:              standalone-chrome  4444/TCP
TargetPort:        4444/TCP
Endpoints:         <none>
Session Affinity:  None
Events:            <none>

CodePudding user response：

There are two problems that I've found from the above-posted YAML and console output.

The selector for service, You've specified as app: standalone-chrome, it should be name: standalone-chrome (if you are trying to access the service from inside kubernetes cluster you can ignore the next problem)
The service type you are trying to access is clusterIp which is only available in your cluster network. For accessing the service from the outside the cluster, use type NodePort. Note that the NodePort services have a predefined range of ports 30000 - 32767. Either you can manually set one port in this range and map it with your 4444 or let Kubernetes randomly pick it for you.

In addition to this, you can use the command kubectl describe service standalone-chrome-service for verifying whether all your pods got attached with the service or not.

CodePudding user response：

Service's syntax with:

  selector:
    app: standalone-chrome

is correct, selector should be matched by label.

Services match a set of Pods using labels and selectors, a grouping primitive that allows logical operation on objects in Kubernetes. Labels are key/value pairs attached to objects

See for more details Using a Service to Expose Your App.

Now you need to add this label (which is app: standalone-chrome) to your pod.yaml metadata:

apiVersion: v1
kind: Pod
metadata:
  name: standalone-chrome
  labels:
    app: standalone-chrome # this label should match to selector in service
spec:
  containers:
  - name: standalone-chrome
    image: selenium/standalone-chrome
    ports:
    - containerPort: 4444
    env:
    - name: JAVA_OPTS
      value: '-Dwebdriver.chrome.whitelistedIps=""'