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📘 DevOps Task – CI/CD with Jenkins, Docker, and Terraform

This project demonstrates a CI/CD pipeline using Jenkins, DockerHub, and Terraform for deploying a Node.js application into an AWS ECS Fargate Cluster.

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📊 Architecture Diagram

Application Access

✅ Once deployed, access the running Node.js app at:

http://54.234.64.42:3000

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⚙️ Setup Instructions

1. EC2 Setup

• Launch an EC2 instance (Amazon Linux 2, default VPC).

• Create a Security Group allowing:

  • 22 (SSH)
  • 80 (HTTP)
  • 3000 (App)
  • 8080 (Jenkins)

2. Install Java & Jenkins

# Install Java 17
sudo amazon-linux-extras enable corretto17
sudo yum install -y java-17-amazon-corretto

# Add Jenkins repo & install Jenkins
sudo wget -O /etc/yum.repos.d/jenkins.repo https://pkg.jenkins.io/redhat-stable/jenkins.repo
sudo rpm --import https://pkg.jenkins.io/redhat-stable/jenkins.io.key
sudo yum install -y jenkins

# Start & enable Jenkins
sudo systemctl start jenkins
sudo systemctl enable jenkins

• Add sudo permission for Jenkins user:

  sudo visudo
  jenkins ALL=(ALL) NOPASSWD:ALL

• Access Jenkins at:

  http://<EC2_PUBLIC_IP>:8080
  

3. Jenkins Configuration

• Install plugins: Git, Docker, Terraform, NodeJS, Pipeline, AWS Credentials.

• Add credentials:

  • dockercred → DockerHub username/password
  • aws-creds → AWS Access Key/Secret

4. GitHub Repo

Repo (devops-task1) contains:

• Node.js application
• Dockerfile
• Terraform configs (main.tf)

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🔄 Jenkins Pipeline Flow

The pipeline (devops-task-CICD) is defined in Jenkinsfile with the following stages:

1. Setup Environment

• Updates system.
• Installs Git, Docker, Terraform, Node.js (via NVM).
• Verifies installations.

2. Clone Repository

• Removes old repo.
• Clones GitHub repo (main branch).

3. Install Dependencies

• Runs npm install for Node.js app.

4. Docker Login

• Logs in to DockerHub using Jenkins credentials.

5. Build Docker Image

• Builds Docker image saihari1/devopstask.

6. Push Docker Image

• Pushes image to DockerHub.

7. Terraform Destroy

• Cleans up old infra before redeploy.

8. Terraform Init

• Initializes Terraform working directory.

9. Terraform Plan

• Creates execution plan (tfplan).

10. Terraform Apply

• Applies infra changes: ECS Cluster, ECS Service, IAM Role, S3 backend, Log Group.

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🌐 Terraform Configuration Breakdown

1. Provider

provider "aws" {
  region = "us-east-1"
}

Sets AWS region.

2. Backend (S3)

terraform {
  backend "s3" {
    bucket       = "my-rehydration-demo"
    key          = "ecs/prod/terraform.tfstate"
    region       = "us-east-1"
    encrypt      = true
    use_lockfile = true
  }
}

Stores Terraform state in S3 (remote backend).

3. CloudWatch Log Group

resource "aws_cloudwatch_log_group" "ecs_logs" {
  name              = "/ecs/devopstask"
  retention_in_days = 7
}

Centralized logs for ECS containers.

4. Networking (Default VPC + Subnets)

data "aws_vpc" "default" { default = true }
data "aws_subnets" "default" {
  filter {
    name   = "vpc-id"
    values = [data.aws_vpc.default.id]
  }
}

Uses default VPC & subnets.

5. Security Group

resource "aws_security_group" "ecs_sg" {
  ingress { from_port = 3000 to_port = 3000 protocol = "tcp" cidr_blocks = ["0.0.0.0/0"] }
  egress  { from_port = 0 to_port = 0 protocol = "-1" cidr_blocks = ["0.0.0.0/0"] }
}

Allows inbound traffic on 3000, open egress.

6. ECS Cluster

resource "aws_ecs_cluster" "cluster" {
  name = "prod-fargate-cluster"
}

Defines ECS Fargate cluster.

7. IAM Role

resource "aws_iam_role" "ecs_task_execution_role" { ... }
resource "aws_iam_role_policy_attachment" "ecs_policy_attach" { ... }

Grants ECS tasks permission to pull images and write logs.

8. ECS Task Definition

resource "aws_ecs_task_definition" "task" {
  family = "devopstask-prod"
  container_definitions = jsonencode([{
    name = "app"
    image = "saihari1/devopstask:latest"
    portMappings = [{ containerPort = 3000 }]
    logConfiguration = { awslogs-group = aws_cloudwatch_log_group.ecs_logs.name }
  }])
}

Defines how the container runs (image, CPU, memory, port, logging).

9. ECS Service

resource "aws_ecs_service" "service" {
  cluster = aws_ecs_cluster.cluster.id
  task_definition = aws_ecs_task_definition.task.arn
  desired_count = 1
  launch_type = "FARGATE"
  network_configuration {
    subnets = data.aws_subnets.default.ids
    security_groups = [aws_security_group.ecs_sg.id]
    assign_public_ip = true
  }
}

Runs ECS tasks as a scalable Fargate service.

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✅ Evaluation Coverage

• GitHub commits/branching → Code in main branch.
• Working Jenkins pipeline → Automates CI/CD.
• Docker best practices → Containerized app with image push.
• Cloud deployment correctness → ECS Fargate + Terraform infra.
• IaC bonus → Terraform for ECS, IAM, S3, CloudWatch.
• Clarity → Diagram + setup + pipeline + Terraform explained.

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