189 lines
6.9 KiB
Markdown
189 lines
6.9 KiB
Markdown
# 🚀 AWS Scalable Web Application — ALB + ASG
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A production-grade, self-healing web application deployed on AWS using an Application Load Balancer, Auto Scaling Group, and EC2 across multiple Availability Zones. Mimics how platforms like **Heroku / Railway** manage scalable deployments automatically.
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---
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## 📸 Screenshots
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> All build screenshots are available in the [`/images`](./images) folder, numbered `1` through `81` in chronological build order.
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**Key screenshots inline:**
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### App Running via ALB DNS
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> App served through the Application Load Balancer DNS — no direct EC2 IP
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### Target Group — Both Instances Healthy in different AZ's
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> Both EC2 instances passing health checks across two Availability Zones
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### Auto Scaling Group — Instance Management after deleting
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> ASG maintaining desired capacity across `ap-south-1a` and `ap-south-1b` after terminating an ec2 machine to check for auto healing
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### AWS Notification -Subscription email
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>Confirmed notification subscription
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### CloudWatch Monitoring Dashboard
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> Real-time metrics — CPU, request count, response time, instance count
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----
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## 🏗️ Architecture
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```
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Internet
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│
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▼
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Internet Gateway (scalable-webapp-igw)
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│
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▼
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┌─────────────────────────────────────────────────────────┐
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│ VPC: scalable-webapp-vpc (10.0.0.0/16) │
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│ │
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│ ┌──────────────────┐ ┌──────────────────┐ │
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│ │ public-subnet-1a │ │ public-subnet-1b │ │
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│ │ 10.0.1.0/24 │ │ 10.0.2.0/24 │ │
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│ └──────────────────┘ └──────────────────┘ │
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│ │ │ │
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│ ▼ ▼ │
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│ Application Load Balancer (webapp-alb) │
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│ │ HTTP :80 Listener │
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│ ▼ │
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│ Target Group (webapp-target-group) │
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│ ├──▶ EC2 t3.micro — ap-south-1a ✓ healthy │
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│ └──▶ EC2 t3.micro — ap-south-1b ✓ healthy │
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│ ▲ │
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│ Auto Scaling Group (webapp-asg) │
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│ min: 1 │ desired: 2 │ max: 4 │
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│ CPU > 50% → scale out │
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│ CPU < 30% → scale in │
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│ │ │
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│ Launch Template (webapp-launch-template) │
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│ Amazon Linux 2023 + nginx │
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└─────────────────────────────────────────────────────────┘
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```
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---
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## ⚙️ AWS Services Used
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| Service | Purpose |
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|---|---|
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| **VPC** | Isolated network with public subnets across 2 AZs |
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| **EC2** | Compute — runs nginx web server |
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| **Application Load Balancer** | Distributes traffic, health checks, single DNS entry |
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| **Auto Scaling Group** | Automatically adds/removes instances based on CPU |
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| **Launch Template** | Blueprint for identical EC2 instances |
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| **IAM Role** | EC2 permissions for S3 and CloudWatch |
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| **CloudWatch** | Metrics dashboard + CPU alarm via SNS email |
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| **Security Groups** | Layered firewall — ALB faces internet, EC2 accepts ALB only |
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---
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## 🔐 Security Design
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```
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Internet → alb-sg (HTTP 0.0.0.0/0)
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↓
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ec2-sg (HTTP from alb-sg ONLY)
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```
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EC2 instances are **not directly reachable** from the internet. All public traffic flows through the ALB only. This is a standard production security pattern.
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---
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## 📦 Infrastructure Summary
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### VPC & Networking
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| Resource | Value |
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|---|---|
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| VPC CIDR | `10.0.0.0/16` |
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| Public Subnet 1 | `10.0.1.0/24` — ap-south-1a |
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| Public Subnet 2 | `10.0.2.0/24` — ap-south-1b |
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| Internet Gateway | Attached to VPC |
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| Route Table | `0.0.0.0/0 → IGW` |
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### Compute
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| Resource | Value |
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|---|---|
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| AMI | Amazon Linux 2023 |
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| Instance Type | t3.micro |
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| Web Server | nginx |
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| Deployment | User data script on launch |
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### Auto Scaling
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| Setting | Value |
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|---|---|
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| Minimum | 1 |
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| Desired | 2 |
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| Maximum | 4 |
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| Scale-out trigger | CPU > 50% |
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| Scale-in trigger | CPU < 30% |
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### Monitoring
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| Resource | Value |
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|---|---|
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| Dashboard | `webapp-monitoring` |
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| Alarm | `webapp-high-cpu` — triggers at 70% |
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| Notification | SNS email alert |
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---
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## 🛠️ Build Phases
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| Phase | What was built |
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| 1 — Networking | VPC, subnets, IGW, route table, security groups |
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| 2 — Compute | Launch template, IAM role, test EC2, nginx + web app |
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| 3 — Auto Scaling | ASG with target tracking scaling policy |
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| 4 — Load Balancer | ALB, target group, listener, ASG integration |
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| 5 — Monitoring | CloudWatch dashboard, CPU alarm, SNS notification |
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---
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## 💡 Key Cloud Concepts Demonstrated
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- **High Availability** — workload spread across 2 Availability Zones
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- **Horizontal Scaling** — ASG adds instances under load, removes them when idle
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- **Self-healing Infrastructure** — failed instances are automatically replaced by ASG
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- **Security Layering** — EC2 not exposed directly, traffic flows ALB → EC2 only
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- **Infrastructure as a Blueprint** — Launch Templates ensure every instance is identical
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- **Observability** — CloudWatch dashboard + proactive alerting via SNS
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---
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## 🧹 Cleanup
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To avoid AWS charges after testing:
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1. Delete **Auto Scaling Group** (this terminates all EC2 instances)
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2. Delete **Application Load Balancer**
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3. Delete **Target Group**
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4. Delete **Launch Template**
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5. Delete **CloudWatch Alarms and Dashboard**
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6. Delete **VPC** (also removes subnets, IGW, route tables, security groups)
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7. Delete **IAM Role** `ec2-webapp-role`
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8. Delete **SNS Topic** `webapp-cpu-alert`
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---
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## 📁 Repository Structure
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```
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aws-scalable-webapp-alb/
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├── index.html # Web app deployed on EC2 via nginx
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├── README.md # This file
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└── images/ # All build screenshots (1–70, in chronological order)
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```
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---
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## Learning Journey
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Built as part of a hands-on AWS Cloud & DevOps learning journey. |