199 lines
6.5 KiB
Markdown
199 lines
6.5 KiB
Markdown
## Selenium on Kubernetes
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Selenium is a browser automation tool used primarily for testing web applications. However when Selenium is used in a CI pipeline to test applications, there is often contention around the use of Selenium resources. This example shows you how to deploy Selenium to Kubernetes in a scalable fashion.
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### Prerequisites
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This example assumes you have a working Kubernetes cluster and a properly configured kubectl client. See the [Getting Started Guides](../../docs/getting-started-guides/) for details.
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Google Container Engine is also a quick way to get Kubernetes up and running: https://cloud.google.com/container-engine/
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Your cluster must have 4 CPU and 6 GB of RAM to complete the example up to the scaling portion.
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### Deploy Selenium Grid Hub:
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We will be using Selenium Grid Hub to make our Selenium install scalable via a master/worker model. The Selenium Hub is the master, and the Selenium Nodes are the workers(not to be confused with Kubernetes nodes). We only need one hub, but we're using a replication controller to ensure that the hub is always running:
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```console
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kubectl create --filename=examples/selenium/selenium-hub-rc.yaml
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```
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The Selenium Nodes will need to know how to get to the Hub, let's create a service for the nodes to connect to.
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```console
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kubectl create --filename=examples/selenium/selenium-hub-svc.yaml
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```
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### Verify Selenium Hub Deployment
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Let's verify our deployment of Selenium hub by connecting to the web console.
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#### Kubernetes Nodes Reachable
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If your Kubernetes nodes are reachable from your network, you can verify the hub by hitting it on the nodeport. You can retrieve the nodeport by typing `kubectl describe svc selenium-hub`, however the snippet below automates that by using kubectl's template functionality:
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```console
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export NODEPORT=`kubectl get svc --selector='app=selenium-hub' --output=template --template="{{ with index .items 0}}{{with index .spec.ports 0 }}{{.nodePort}}{{end}}{{end}}"`
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export NODE=`kubectl get nodes --output=template --template="{{with index .items 0 }}{{.metadata.name}}{{end}}"`
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curl http://$NODE:$NODEPORT
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```
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#### Kubernetes Nodes Unreachable
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If you cannot reach your Kubernetes nodes from your network, you can proxy via kubectl.
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```console
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export PODNAME=`kubectl get pods --selector="app=selenium-hub" --output=template --template="{{with index .items 0}}{{.metadata.name}}{{end}}"`
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kubectl port-forward --pod=$PODNAME 4444:4444
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```
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In a separate terminal, you can now check the status.
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```console
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curl http://localhost:4444
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```
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#### Using Google Container Engine
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If you are using Google Container Engine, you can expose your hub via the internet. This is a bad idea for many reasons, but you can do it as follows:
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```console
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kubectl expose rc selenium-hub --name=selenium-hub-external --labels="app=selenium-hub,external=true" --create-external-load-balancer=true
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```
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Then wait a few minutes, eventually your new `selenium-hub-external` service will be assigned a load balanced IP from gcloud. Once `kubectl get svc selenium-hub-external` shows two IPs, run this snippet.
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```console
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export INTERNET_IP=`kubectl get svc --selector="app=selenium-hub,external=true" --output=template --template="{{with index .items 0}}{{with index .status.loadBalancer.ingress 0}}{{.ip}}{{end}}{{end}}"`
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curl http://$INTERNET_IP:4444/
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```
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You should now be able to hit `$INTERNET_IP` via your web browser, and so can everyone else on the Internet!
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### Deploy Firefox and Chrome Nodes:
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Now that the Hub is up, we can deploy workers.
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This will deploy 2 Chrome nodes.
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```console
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kubectl create --file=examples/selenium/selenium-node-chrome-rc.yaml
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```
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And 2 Firefox nodes to match.
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```console
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kubectl create --file=examples/selenium/selenium-node-firefox-rc.yaml
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```
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Once the pods start, you will see them show up in the Selenium Hub interface.
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### Run a Selenium Job
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Let's run a quick Selenium job to validate our setup.
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#### Setup Python Environment
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First, we need to start a python container that we can attach to.
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```console
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kubectl run selenium-python --image=google/python-hello
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```
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Next, we need to get inside this container.
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```console
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export PODNAME=`kubectl get pods --selector="run=selenium-python" --output=template --template="{{with index .items 0}}{{.metadata.name}}{{end}}"`
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kubectl exec --stdin=true --tty=true $PODNAME bash
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```
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Once inside, we need to install the Selenium library
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```console
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pip install selenium
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```
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#### Run Selenium Job with Python
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We're all set up, start the python interpreter.
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```console
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python
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```
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And paste in the contents of selenium-test.py.
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```python
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from selenium import webdriver
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from selenium.webdriver.common.desired_capabilities import DesiredCapabilities
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def check_browser(browser):
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driver = webdriver.Remote(
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command_executor='http://selenium-hub:4444/wd/hub',
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desired_capabilities=getattr(DesiredCapabilities, browser)
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)
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driver.get("http://google.com")
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assert "google" in driver.page_source
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driver.close()
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print("Browser %s checks out!" % browser)
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check_browser("FIREFOX")
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check_browser("CHROME")
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```
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You should get
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```
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>>> check_browser("FIREFOX")
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Browser FIREFOX checks out!
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>>> check_browser("CHROME")
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Browser CHROME checks out!
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```
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Congratulations, your Selenium Hub is up, with Firefox and Chrome nodes!
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### Scale your Firefox and Chrome nodes.
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If you need more Firefox or Chrome nodes, your hardware is the limit:
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```console
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kubectl scale rc selenium-node-firefox --replicas=10
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kubectl scale rc selenium-node-chrome --replicas=10
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```
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You now have 10 Firefox and 10 Chrome nodes, happy Seleniuming!
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### Debugging
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Sometimes it is necessary to check on a hung test. Each pod is running VNC. To check on one of the browser nodes via VNC, it's recommended that you proxy, since we don't want to expose a service for every pod, and the containers have a weak VNC password. Replace POD_NAME with the name of the pod you want to connect to.
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```console
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kubectl port-forward --pod=POD_NAME 5900:5900
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```
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Then connect to localhost:5900 with your VNC client using the password "secret"
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Enjoy your scalable Selenium Grid!
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Adapted from: https://github.com/SeleniumHQ/docker-selenium
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### Teardown
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To remove all created resources, run the following:
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```console
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kubectl delete rc selenium-hub
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kubectl delete rc selenium-node-chrome
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kubectl delete rc selenium-node-firefox
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kubectl delete deployment selenium-python
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kubectl delete svc selenium-hub
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kubectl delete svc selenium-hub-external
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```
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<!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
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