Unveiling the Powerful Selenium Grid Architecture [ 2024 ]
Selenium Grid Architecture
Selenium Grid Architecture is a system designed to distribute the test execution across multiple machines, enabling parallel test execution in different environments and browsers. This setup improves the speed of running automated tests and helps in achieving cross-browser and cross-platform testing.
Selenium Grid is an automation tool used with Selenium WebDriver to run distributed web tests simultaneously on multiple machines and browsers. This allows for parallel test execution, significantly reducing the time required to execute a test suite. The architecture of Selenium Grid is based on a hub-node model.
Components
Selenium Grid = A Hub + Multiple Nodes
Hub
You can have only one Hub in a Selenium Grid setup.
The Hub is the central server in Selenium Grid that controls the test distribution to various machines (nodes). It acts as the main point of communication between the test scripts and the Nodes.
The Hub can be thought of as the coordinator of the tests. It receives the test requests from the clients (scripts) and sends them to the appropriate nodes for execution.
Node
You can have multiple Nodes in a Selenium Grid setup.
Nodes are the machines either physical or virtual connected to the Hub, where the actual tests are executed. Nodes can run tests on different browsers, operating systems, and environments. A Node registers itself with the Hub to receive test requests. Each Node can run multiple browsers in parallel and is configured to support specific browsers (e.g., Chrome, Firefox, Edge) and platforms (e.g., Windows, Linux, Mac OS).
Architecture Diagram
Below is an example architecture diagram for running tests on Linux, Windows, and Mac platforms. As shown in the diagram, a hub distributes the test across the nodes.
As shown in the figure, Selenium Grid allows us to run multiple instances of nodes in parallel on different OSs. All the tests can run in parallel on multiple browsers on different OSs, such as Safari on Mac or Firefox on a Linux machine. Selenium Grid makes all these nodes appear as a single instance, so tests do not have to worry about the infrastructure. It cuts down on the time required to run Selenium tests.
Selenium Client
The Client is the code (test script) that sends the test request to the Hub, specifying the desired browser, operating system, and other parameters. The client communicates with the Hub to request the execution of test cases, and the Hub forwards the request to an appropriate Node based on the configuration and availability.
