In this blog, we’ll explore how Jenkins integrates with these tools using a master-slave configuration — with a simple example to tie it all together.


Understanding Jenkins Master-Slave Setup

- Master Node: Controls the Jenkins environment, handles scheduling, and assigns jobs to slaves


- Slave Node (Agent): Performs the actual tasks like pulling code, building Docker containers, or running test scripts.


This separation of responsibilities ensures that heavy tasks don't overload the master and builds/tests can run in parallel.

"The best way to secure a system is not to have it accessible in the first place."

by Eugene H. Spafforda

Integrating Git, Docker, and Selenium — Step-by-Step Example


Scenario:

You're developing a web application. You want Jenkins to:
1. Pull the latest code from Git.
2. Build and containerize the app using Docker.
3. Run Selenium test cases to verify the UI.

Step 1: Git Integration on Jenkins Master

  • The Jenkins master monitors the Git repository for changes.
  • When a developer pushes code to GitHub, a webhook triggers a Jenkins job.
  • Jenkins pulls the source code and schedules the pipeline execution.
Step 2: Docker Build on Slave Node

  • The Jenkins slave (with Docker installed) receives the build job.
  • It creates a Docker image of the application using the pulled source code.
  • The image is then run as a container for further testing or deployment.
Step 3: Selenium Testing on Slave Node

  • Another Jenkins slave (configured with Selenium and browser drivers) picks up the nextstage
  • It runs automated Selenium scripts against the Dockerized app to verify the UI.
  • Test results are sent back to the Jenkins master for reporting.
Final Workflow Summary
[ Git Repo Push ] → [ Jenkins Master ]
1. Clone Git →
2. Assign Build to Docker Slave →
3. Assign Tests to Selenium Slave
[ Report Back to Master ]

Why Use Jenkins with Master-Slave Setup?


  • Load distribution across nodes
  • Environment isolation for builds and tests
  • Faster execution with parallel tasking
  • Scalability for enterprise pipelines

Final Thoughts


Integrating Jenkins with Git, Docker, and Selenium in a master-slave environment creates a reliable, scalable, and automated DevOps pipeline. You ensure that every code commit is built, tested, and packaged — without slowing down your infrastructure or your team.

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