How to connect multiple machines to the Selenium Grid hub

istvan.lackoOctober 31, 2013Automated Testing Tools, JavaComments are off for this post

There might an instance in which we would want to run, for example, 50 tests in parallel.
50 browsers would consume the CPU power very fast, so we need to split the load between multiple machines.
Fortunately with Selenium Grid 2 this is not a problem.

On “Machine A” we need to start the Grid hub with the following command:

java -jar selenium-server-standalone-2.35.0.jar -role hub -port 5555

To “Machine A” we can give the number of the maximum Sessions, to control how many browser may run in parallel.
The following command starts a node on “Machine A”, plus gives the number of Sessions:

java -jar selenium-server-standalone-2.35.0.jar -role node -hub http://localhost:5555/grid/register -browser browserName=chrome,maxInstances=25 -maxSession 25

On the remote machines we also need to set up the selenium grid. For this we need the selenium-server-standalone-2.35.0.jar file, need to set up the java environment and add the browser drivers (chromedriver, iedriver) to the environment variables.
Then on “Machine B” we can register the remote machine to the hub with the following command:
java -jar selenium-server-standalone-2.35.0.jar -role node -hub http://TheHubIP:5555/grid/register -browser browserName=chrome,maxInstances=25 -maxSession 25

Of course you need to add the hub IP to the “TheHubIP” part.

6 thoughts to “How to connect multiple machines to the Selenium Grid hub”

Aditya January 23, 2014 at 2:45 pm

Just curious to know, what is the difference between maxinstances and maxsessions arguements while running node.
- István Lackó February 3, 2014 at 7:43 am
  
  Hi,
  The answer is the following:
  MaxInstances – how many instances of same version of browser can run over the Remote System. So I can run X instances of Firefox and as well as Y instances of IE at the same time in remote machine. So total user can run X+Y instances of different browsers in parallel.
  MaxSession – how many browsers (Any Browser and any version) can run in parallel at a time in the remote system. So this overrides the Max Instances settings and can restrict the number of browser instances that can run in parallel.
Asiq Ahamed February 20, 2014 at 11:50 am

VisGrid-UI for Selenium Grid

VisGrid is a GUI for Selenium Grid. You can start hub, create and attach a Selenium node very easily and quickly.

Download: http://www.codoid.com/products/view/2/30
- Tihomir Turzai February 21, 2014 at 9:40 am
  
  Hi Asiq,
  
  Thanks for the tip. We more like the console configuration because of the flexibility, but we will try out your tool too, maybe we can spare some time with it.
Silas Ray September 19, 2014 at 5:48 pm

It should be noted that it’s often advisable not to run a node on the same machine as the hub, as is done here. While the hub doesn’t consume much in the way of CPU and memory resources, both the hub and the test client (the code actually executing the tests remotely through Selenium) consume lots of network resources, which can start to bog the system down, especially if your test code is interacting a lot with Selenium. The hub acts as a proxy to the remotes, so running the hub and node on the same machine essentially doubles network traffic on the loopback interface vs running the same number of instances purely locally.
Ishwaryaa January 26, 2017 at 11:46 am

Thanks for the article,
Could you please help me here – I am running my GridServer and Nodes on the cloud. Shall I make a p2p connection between grids.