ECS with ALB integration in AWS - Mini Project: Build & Apply

ECS with ALB integration

📖 Scenario: You are setting up a simple web application on AWS using Elastic Container Service (ECS) with an Application Load Balancer (ALB) to distribute traffic.This setup helps your app handle more users by spreading requests across multiple containers.

🎯 Goal: Build an ECS service running a container behind an Application Load Balancer (ALB) that routes HTTP traffic to the container.You will create the ECS cluster, task definition, ALB, target group, and ECS service with ALB integration.

📋 What You'll Learn

Create an ECS cluster named my-ecs-cluster

Define a task definition named my-task-def with a container named my-container using the image nginx:latest

Create an Application Load Balancer named my-alb with a listener on port 80

Create a target group named my-target-group for the ALB with port 80 and protocol HTTP

Create an ECS service named my-ecs-service that runs 2 tasks and integrates with the ALB target group

💡 Why This Matters

🌍 Real World

This project shows how to deploy containerized web applications on AWS ECS with load balancing to handle user traffic efficiently.

💼 Career

Understanding ECS and ALB integration is essential for cloud engineers and DevOps professionals managing scalable containerized applications.

1

Create ECS cluster

Create an ECS cluster named my-ecs-cluster using AWS CLI syntax.

AWS

# Create ECS cluster named my-ecs-cluster
# Your code here

Hint

Use the AWS CLI command aws ecs create-cluster --cluster-name my-ecs-cluster to create the cluster.

2

Define ECS task definition

Create a task definition JSON file named task-def.json with a container named my-container using the image nginx:latest and port 80 exposed. Register the task definition.

AWS

aws ecs create-cluster --cluster-name my-ecs-cluster
# Create task definition JSON file task-def.json and register it
# Your code here

Hint

Create the JSON file using cat > task-def.json << 'EOF' ... EOF with family as my-task-def and a container named my-container using nginx:latest image exposing port 80. Then register with aws ecs register-task-definition --cli-input-json file://task-def.json.

3

Create Application Load Balancer and target group

Create an Application Load Balancer named my-alb with a listener on port 80 and a target group named my-target-group with protocol HTTP and port 80.

AWS

aws ecs create-cluster --cluster-name my-ecs-cluster
cat > task-def.json << 'EOF'
{
  "family": "my-task-def",
  "containerDefinitions": [
    {
      "name": "my-container",
      "image": "nginx:latest",
      "portMappings": [
        {
          "containerPort": 80,
          "protocol": "tcp"
        }
      ]
    }
  ]
}
EOF
aws ecs register-task-definition --cli-input-json file://task-def.json
# Create ALB named my-alb with listener on port 80 and target group my-target-group
# Your code here

Hint

Use aws elbv2 create-load-balancer to create ALB and aws elbv2 create-target-group for the target group. Then create a listener on port 80 forwarding to the target group.

4

Create ECS service with ALB integration

Create an ECS service named my-ecs-service in cluster my-ecs-cluster that runs 2 tasks of my-task-def and integrates with the ALB target group my-target-group.

AWS

aws ecs create-cluster --cluster-name my-ecs-cluster
cat > task-def.json << 'EOF'
{
  "family": "my-task-def",
  "containerDefinitions": [
    {
      "name": "my-container",
      "image": "nginx:latest",
      "portMappings": [
        {
          "containerPort": 80,
          "protocol": "tcp"
        }
      ]
    }
  ]
}
EOF
aws ecs register-task-definition --cli-input-json file://task-def.json
aws elbv2 create-load-balancer --name my-alb --subnets subnet-12345678 subnet-87654321 --security-groups sg-12345678
aws elbv2 create-target-group --name my-target-group --protocol HTTP --port 80 --vpc-id vpc-12345678
aws elbv2 create-listener --load-balancer-arn arn:aws:elasticloadbalancing:region:account-id:loadbalancer/app/my-alb/1234567890abcdef --protocol HTTP --port 80 --default-actions Type=forward,TargetGroupArn=arn:aws:elasticloadbalancing:region:account-id:targetgroup/my-target-group/abcdef1234567890
# Create ECS service my-ecs-service with 2 tasks and ALB integration
# Your code here

Hint

Use aws ecs create-service with cluster, service name, task definition, desired count 2, and load balancer target group ARN with container name and port.

Practice

1. What is the main purpose of integrating an Application Load Balancer (ALB) with Amazon ECS?

easy

A. To distribute incoming web traffic evenly across multiple container tasks

B. To store container images securely

C. To monitor CPU usage of ECS tasks

D. To create virtual private clouds automatically

Solution

1. Step 1: Understand ALB role in ECS

   ALB is designed to balance incoming traffic to multiple targets, such as ECS tasks, to ensure reliability and scalability.

2. Step 2: Identify the correct purpose

   Among the options, only distributing web traffic evenly matches ALB's function in ECS.

3. Final Answer:

   To distribute incoming web traffic evenly across multiple container tasks -> Option A

4. Quick Check:

   ALB balances traffic = C [OK]

Hint: ALB balances traffic to containers, not stores or monitors [OK]

Common Mistakes:

• Confusing ALB with container image storage
• Thinking ALB monitors CPU usage
• Assuming ALB creates VPCs

2. Which ECS launch type and network mode combination is recommended for simple networking and security when using ALB?

easy

A. EC2 launch type with none network mode

B. EC2 launch type with bridge network mode

C. Fargate launch type with host network mode

D. Fargate launch type with awsvpc network mode

Solution

1. Step 1: Recall recommended ECS and network mode

   Fargate with awsvpc mode provides each task with its own network interface, simplifying networking and security.

2. Step 2: Match options to recommendation

   Only Fargate launch type with awsvpc network mode matches the recommended combination for ALB integration.

3. Final Answer:

   Fargate launch type with awsvpc network mode -> Option D

4. Quick Check:

   Fargate + awsvpc = A [OK]

Hint: Fargate + awsvpc = simple networking with ALB [OK]

Common Mistakes:

• Choosing EC2 launch type instead of Fargate
• Using bridge or host network modes with Fargate
• Selecting none network mode which disables networking

3. Given this ECS service configuration snippet, what will happen when the ALB receives HTTP requests?

{
  "loadBalancers": [{
    "targetGroupArn": "arn:aws:elasticloadbalancing:...",
    "containerName": "webapp",
    "containerPort": 80
  }],
  "launchType": "FARGATE",
  "networkConfiguration": {
    "awsvpcConfiguration": {
      "subnets": ["subnet-12345"],
      "assignPublicIp": "ENABLED"
    }
  }
}

medium

A. ALB forwards requests to the webapp container on port 80 in each task

B. ALB blocks all HTTP requests due to missing security group

C. ALB forwards requests to port 443 by default

D. ALB cannot route because containerPort is missing

Solution

1. Step 1: Analyze load balancer target settings

   The ALB targets the container named "webapp" on port 80, so it will forward HTTP requests there.

2. Step 2: Check network configuration

   Fargate with awsvpc and public IP enabled allows tasks to receive traffic from ALB.

3. Final Answer:

   ALB forwards requests to the webapp container on port 80 in each task -> Option A

4. Quick Check:

   ALB targets container port 80 = B [OK]

Hint: ALB forwards to specified containerPort, not default 443 [OK]

Common Mistakes:

• Assuming ALB blocks traffic without explicit security group mention
• Thinking ALB defaults to port 443
• Missing containerPort causes routing failure

4. You deployed an ECS service with ALB integration but the ALB shows no healthy targets. What is the most likely cause?

medium

A. The ECS cluster has no EC2 instances running

B. The ALB listener is missing a rule for HTTPS traffic

C. The ECS tasks are not registering with the target group due to incorrect container port mapping

D. The ALB is in a different AWS region than the ECS service

Solution

1. Step 1: Understand why ALB shows no healthy targets

   ALB health checks fail if ECS tasks do not register correctly, often due to wrong container port mapping.

2. Step 2: Evaluate other options

   Listener rules missing HTTPS won't cause no healthy targets; ECS Fargate doesn't need EC2 instances; ALB and ECS must be in same region, but this is less common cause.

3. Final Answer:

   The ECS tasks are not registering with the target group due to incorrect container port mapping -> Option C

4. Quick Check:

   Incorrect port mapping blocks target registration = A [OK]

Hint: Check container port matches target group port for healthy targets [OK]

Common Mistakes:

• Assuming missing HTTPS rule causes no healthy targets
• Thinking ECS Fargate needs EC2 instances
• Ignoring region mismatch issues

5. You want to deploy a highly available ECS service behind an ALB that automatically scales with traffic. Which combination of settings ensures this best practice?

hard

A. Use EC2 launch type with none mode, ALB with health checks disabled, and ECS service with fixed task count

B. Use Fargate launch type with awsvpc mode, ALB with target group health checks, and ECS service auto scaling

C. Use Fargate launch type with host mode, ALB with fixed target group size, and no ECS scaling

D. Use EC2 launch type with bridge mode, ALB without health checks, and manual ECS task scaling

Solution

1. Step 1: Identify best ECS launch and network mode for availability

   Fargate with awsvpc mode simplifies networking and security, ideal for high availability.

2. Step 2: Confirm ALB and ECS scaling features

   ALB target group health checks ensure traffic only goes to healthy tasks; ECS service auto scaling adjusts task count with traffic.

3. Step 3: Evaluate other options

   Other options lack health checks or auto scaling, reducing availability and scalability.

4. Final Answer:

   Use Fargate launch type with awsvpc mode, ALB with target group health checks, and ECS service auto scaling -> Option B

5. Quick Check:

   Fargate + awsvpc + ALB health checks + auto scaling = D [OK]

Hint: Combine Fargate, awsvpc, ALB health checks, and auto scaling [OK]

Common Mistakes:

• Skipping ALB health checks
• Using manual scaling instead of auto scaling
• Choosing EC2 with bridge or none network modes