Selenium Grid & Docker container Implementation

by Niranjan Limbachiya | May 11, 2016 | Manual TestingSelenium Automation Testing | 0 Comment

What is Docker?

Docker is a lightweight container (read: a scaled-down VM) that provides a fast and programmatic way to run distributed applications. Selenium Grid is distributed system of nodes for running tests. Instead of running your grid across multiple machines or VMs, you can run them all on a single large machine using Docker. The two are practically destined for each other.

What is Selenium Grid?

Selenium Grid is a great way to speed up your tests by running them in parallel on multiple machines. However, rolling your own grid also means maintaining it. Setting up the right browser / OS combinations across many virtual machines (or – even worse – physical machines) and making sure each is running the Selenium Server correctly is a huge pain.

How to run selenium grid with Docker:

You can check at below link to see information.
  1. https://docs.docker.com/compose/install/
  2. https://docs.docker.com/installation/
  • Here’s an overview of what we’re going to do: 1. Create Docker images for your Selenium Grid hub and node(s) 2. Add Java to the hub to run the Selenium server jar 3. Add Java, plus Firefox and Xvfb to the node 4. Create a docker-compose.yml file to define how the images will interact with each other 5. Start docker-compose and scale out to as many nodes as you need – or that your machine can handlet

Create a base image for your selenium server and the hub

let’s make a base Dockerfile we can use for both:

FROM ubuntu

ENV VERSION 2.44.0

RUN apt-get update -qqy \
&& apt-get -qqy --no-install-recommends install \
software-properties-common \
&& rm -rf /var/lib/apt/lists/*
RUN add-apt-repository -y ppa:webupd8team/java

RUN echo debconf shared/accepted-oracle-license-v1-1 select true | debconf-set-selections
RUN echo debconf shared/accepted-oracle-license-v1-1 seen true | debconf-set-selections

RUN apt-get update -qqy \
&& apt-get -qqy --no-install-recommends install \
oracle-java7-installer \
&& rm -rf /var/lib/apt/lists/*

RUN wget http://selenium-release.storage.googleapis.com/${VERSION%.*}/selenium-server-standalone-${VERSION}.jar

Let's Build and Tag it

docker build -t selenium/base .
The Grid is basically a single hub connected to any number of different nodes. So, our hub image should look something like this:
FROM selenium/base

EXPOSE 4444

ADD start_grid.sh /var/start_grid.sh
RUN chmod 755 /var/start_grid.sh

CMD ["/bin/bash", "/var/start_grid.sh"]
And in the same directory as the Dockerfile, your run.sh script:
java -jar selenium-server-standalone-${VERSION}.jar -role hub

Install specific version of Firefox

we need a single Dockerfile for all of our nodes. In this example, every node will be a copy of this Dockerfile. It follows the same format as above – start from our selenium/base image and install necessary apps: Firefox, Xvfb, etc. However, there’s one catch here. we need to install a specific version of Firefox. specifying a specific version of Firefox in our Dockerfile is a good rule of thumb:

FROM selenium/base

ENV FIREFOX_MINOR 34.0.5

RUN apt-get update -qqy \
&& apt-get -qqy --no-install-recommends install \
firefox \
xvfb \
bzip2 \
&& rm -rf /var/lib/apt/lists/*

RUN [ -e /usr/bin/firefox ] && rm /usr/bin/firefox
ADD https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/${FIREFOX_MINOR}/linux-x86_64/en-US/firefox-${FIREFOX_MINOR}.tar.bz2 /tmp/
RUN apt-get install -q -y libdbus-glib-1-2
RUN tar -xvjf /tmp/firefox-${FIREFOX_MINOR}.tar.bz2 -C /opt/
RUN chmod -R +x /opt/firefox/
RUN ln -s /opt/firefox/firefox /usr/bin/firefox

ADD register-node.sh /var/register-node.sh
RUN chmod 755 /var/register-node.sh

CMD ["/bin/bash", "/var/register-node.sh"]
And our register-node.sh script:
#!/bin/bash
xvfb-run --server-args=":99.0 -screen 0 2000x2000x16 -ac" \
java -jar selenium-server-standalone-${VERSION}.jar \
-role node \
-hub http://$HUB_1_PORT_4444_TCP_ADDR:4444/grid/register \
-browser browserName=firefox

Define Your selenium Grid network with Docker compose

Once we have these files created, let’s make a docker-compose.yml file in the same directory as our selenium_grid folder. The contents of the file should be as follows:
hub:
  image: selenium_grid/hub
  ports:
    - "4444:4444"
firefox:
  image: selenium_grid/firefox
  links:
    - hub
  expose:
    - "5555"

Docker compose-Up

From here, all we have to do is start it up:
#!/bin/bash
docker-compose up -d
docker-compose scale firefox=5
You should now have a Selenium Grid consisting of one hub and five Firefox nodes. (You can see them running here: http://<boot2docker_ip>:4444/grid/console)

Docker compose-Up & down

Want to scale your grid up or down? It’s easy: just type docker-compose scale firefox=20. Too much? Scale it back down size with docker-compose scale firefox=10. Let’s stop everything. And for good measure, let’s completely remove the images too:
docker-compose stop
docker-compose rm
From here, there are a lot of possibilities for setting up your Grid and integrating it with other Continuous Integration systems.  

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