dev-ops-challenges

Jenkins Deploy Pipeline

Technical Overview

Modern Continuous Integration and Continuous Deployment (CI/CD) pipelines automate software delivery from source control to production web servers. By leveraging Jenkins Pipelines as code, infrastructure teams can define build, test, and deployment workflows within declarative Groovy scripts.

In this challenge, we configure a Jenkins Declarative Pipeline job named datacenter-webapp-job to automate the deployment of a static web application hosted in a Gitea Git repository onto an Apache HTTP web server running on App Server 1 (stapp01).

Key tasks accomplished:

Agent Node Configuration: Configuring an SSH Build Agent Node (App Server 1) with label stapp01 and remote root directory /home/sarah/jenkins_agent.
Pipeline Job Creation: Creating a Jenkins Pipeline project named datacenter-webapp-job.
Declarative Pipeline Scripting: Writing a Groovy pipeline script that restricts execution to nodes labeled stapp01 and defines a single stage named Deploy to pull updates directly into the web root directory (/var/www/html).
Automated Verification: Triggering the pipeline, monitoring console outputs, updating source files in Git, and verifying dynamic updates on the web application.

graph TD
    subgraph SCM ["Gitea Version Control"]
        GitRepo["Git Repository<br/>sarah/web_app master branch"]
    end

    subgraph JenkinsController ["Jenkins Controller"]
        Job["Pipeline Job:<br/>datacenter-webapp-job"]
        Script["Declarative Jenkinsfile<br/>agent { label 'stapp01' }"]
    end

    subgraph AppServer ["App Server 1: stapp01"]
        Agent["Jenkins Agent Process<br/>Root: /home/sarah/jenkins_agent"]
        WebRoot["Apache Web Root<br/>/var/www/html"]
        Apache["Apache Web Server<br/>Port 8091"]
    end

    GitRepo -->|"1. Source Code Push"| Job
    Job -->|"2. Parse Pipeline"| Script
    Script -->|"3. Schedule Job on stapp01"| Agent
    Agent -->|"4. Execute Shell: git pull"| WebRoot
    WebRoot -->|"5. Serve Updated Web Content"| Apache

Pipeline Architecture & Deployment Strategy

1. Declarative Jenkins Pipeline

Unlike classic Freestyle jobs, Jenkins Pipelines use a domain-specific language (DSL) written in Groovy to define execution steps:

pipeline { ... }: The root block enclosing the pipeline definition.
agent { label 'stapp01' }: Directs the Jenkins controller to schedule and execute stages exclusively on agent nodes tagged with the stapp01 label.
stages { stage('Deploy') { ... } }: Defines explicit build phases. The Deploy stage executes shell commands directly within the agent environment.

2. Live Document-Root Pull Deployment

The deployment mechanism navigates to /var/www/html on stapp01 and executes git pull origin master:

Zero-Downtime Update: Pulls updated assets directly into the web root served by Apache HTTP Server.
Fast-Forward Merge: Synchronizes local web root commits with the remote sarah/web_app repository branch.

Infrastructure & Configuration Requirements

Jenkins Controller Access: Web Browser (HTTP) on port 8080
Admin Credentials: admin / Adm!n321
Target Application Server: App Server 1 (stapp01)
Git Repository: http://gitea:3000/sarah/web_app
Required Plugins: Pipeline, SSH Build Agents

Agent Node & Pipeline Matrix

Setting	Value
Node Name	`App Server 1`
Node Label	`stapp01`
Remote Root Directory	`/home/sarah/jenkins_agent`
Launch Method	Launch agents via SSH
Host	`stapp01`
SSH Credentials	`sarah`
Pipeline Job Name	`datacenter-webapp-job`
Pipeline Stage Name	`Deploy`
Web Server Document Root	`/var/www/html`

Step-by-Step Walkthrough

Step 1: Log in to Jenkins

Open your browser and navigate to the Jenkins interface.
Sign in with administrative credentials:
- Username: admin
- Password: Adm!n321

Step 2: Verify Required Plugins

Navigate to Manage Jenkins -> Plugins -> Available plugins and verify that both Pipeline and SSH Build Agents plugins are installed and available.

Jenkins Plugins Setup

Step 3: Configure `App Server 1` SSH Build Agent Node

Navigate to Manage Jenkins -> Nodes.
Select or edit node App Server 1 configuration:
- Remote root directory: /home/sarah/jenkins_agent
- Labels: stapp01
- Launch method: Launch agents via SSH
- Host: stapp01
- Credentials: Select SSH credentials for sarah
- Host Key Verification Strategy: Non verifying Verification Strategy
Click Save.

Configure App Server 1 Node

Step 4: Verify Node Status

Confirm on the Nodes overview page that App Server 1 is online and connected with label stapp01.

Jenkins Nodes Status Page

Step 5: Create New Pipeline Job

Click New Item from the left dashboard menu.
Enter item name: datacenter-webapp-job
Select Pipeline as the item type.
Click OK.

Create Pipeline Job

Step 6: Configure Pipeline Script

In the job configuration page under the Pipeline section, set Definition to Pipeline script and input the following Groovy code:

pipeline {
    agent { label 'stapp01' }

    stages {
        stage('Deploy') {
            steps {
                sh '''
                cd /var/www/html
                git pull origin master
                '''
            }
        }
    }
}

Click Save.

Configure Pipeline Script

Step 7: Build Scheduling & Execution Handling

If the agent node is not tagged with stapp01 or is offline, Jenkins will queue the build with the message: Still waiting to schedule task: There are no nodes with the label 'stapp01'

Build Waiting for Agent Label

Once App Server 1 is properly online with label stapp01, click Build Now.

Step 8: Verify Build Console Output

Open Console Output for Build #3 to verify successful execution:

The build runs on App Server 1 inside workspace /home/sarah/jenkins_agent/workspace/datacenter-webapp-job.
Executes cd /var/www/html && git pull origin master.
Pulls updates from http://gitea:3000/sarah/web_app.
Status completes with Finished: SUCCESS.

Pipeline Execution Console Output

Step 9: Verify Initial Deployed Web Page

Navigate to the web server URL (port 8091). Verify the initial output served from /var/www/html/index.html: Welcome to xFusionCorp Industries!

Initial Deployed Web Application

Step 10: Inspect Source Repository in Gitea

Access the Gitea repository at http://gitea:3000/sarah/web_app and open index.html.

Gitea Web Application Repository

Step 11: Update Source Code & Re-Trigger Deployment

In Gitea, edit index.html to append additional text:

Welcome to xFusionCorp Industries!
This verify the deployment job is running successfully.

Commit changes to the master branch.

Editing index.html in Gitea

Trigger Build Now on datacenter-webapp-job in Jenkins.

Step 12: Confirm Updated Web Application

Refresh the web application URL on port 8091. Confirm the live web page reflects the latest commit: Welcome to xFusionCorp Industries! This verify the deployment job is running successfully.

Updated Web Application Deployment

Complete Declarative Jenkinsfile

pipeline {
    agent { 
        label 'stapp01' 
    }

    stages {
        stage('Deploy') {
            steps {
                sh '''
                cd /var/www/html
                git pull origin master
                '''
            }
        }
    }
}

Verification & Validation Checklist

SSH Build Agent App Server 1 configured with label stapp01 and remote root /home/sarah/jenkins_agent.
Pipeline project datacenter-webapp-job created in Jenkins.
Declarative pipeline script defined with agent { label 'stapp01' } and stage 'Deploy'.
Deployment commands execute git pull origin master inside /var/www/html.
Jenkins build finishes with status SUCCESS.
Web server running on stapp01 correctly serves updated contents from /var/www/html/index.html.