3-Tier Architecture (Part-4)
Dharshinisri G

Dharshinisri G @dharshinisri_g_04a9fda5b6

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Jan 22, 2025

3-Tier Architecture (Part-4)

Publish Date: Mar 31
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AWS Three-Tier Architecture: App Instance Deployment

Table of Contents

App Instance Deployment

  1. Navigate to the EC2 service dashboard and click on Instances on the left-hand side.
  2. Click Launch Instances.

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  1. Select the Amazon Linux 2 AMI.

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  1. Choose t2.micro (Free Tier Eligible) and click Next: Configure Instance Details.

  2. Proceed without key-pair since we will use EC2-instance login.
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  3. Configure the instance details:

    • Select the correct Network (VPC) and Private Subnet (AZ-1). Image description

  • Attach the IAM role created earlier.
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  • Use the private instance security group created before.
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  1. Click Launch Instance.

Connect to Instance

  1. Navigate to the Instances list in the EC2 dashboard.

  2. Once the instance state is running, select it and click Connect.
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  3. Go to the Session Manager tab and click Connect (Opens a new browser tab).

Note: If you cannot connect via Session Manager, ensure:

  • Your instance can route to NAT Gateway.
  • The IAM role has the necessary permissions.
  1. Once connected, switch to ec2-user: 
   sudo -su ec2-user
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  1. Check if the instance can access the internet: 
   ping 8.8.8.8
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  1. If you cannot reach the internet, check Route Tables and Subnet Associations for NAT Gateway routing.

Configure Database

Install MySQL CLI 

sudo yum install mysql -y
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If the above fails, try:

sudo wget https://dev.mysql.com/get/mysql57-community-release-e17-11.noarch.rpm
sudo rpm --import https://repo.mysql.com/RPM-GPG-KEY-mysql-2022
sudo yum install https://dev.mysql.com/get/mysql57-community-release-e17-11.noarch.rpm
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Connect to RDS Database 

mysql -h YOUR-RDS-ENDPOINT -u YOUR-USERNAME -p
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Enter your password when prompted.

Create a Database and Table 

CREATE DATABASE webappdb;
SHOW DATABASES;
USE webappdb;

CREATE TABLE IF NOT EXISTS transactions (
    id INT NOT NULL AUTO_INCREMENT,
    amount DECIMAL(10,2),
    description VARCHAR(100),
    PRIMARY KEY(id)
);

SHOW TABLES;
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Insert Test Data 

INSERT INTO transactions (amount, description) VALUES ('400', 'groceries');
SELECT * FROM transactions;
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Exit MySQL:

exit
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Configure App Instance

Update Database Credentials

  1. Open application-code/app-tier/DbConfig.js.
  2. Update the hostname, user, password, and database.
  3. Save the file.

Upload App Code to S3

  1. Upload the app-tier folder to the S3 bucket created earlier.

Install Node.js and Dependencies 

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.38.0/install.sh | bash
source ~/.bashrc
nvm install 16
nvm use 16
npm install -g pm2
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Download and Run App 

cd ~/
aws s3 cp s3://BUCKET_NAME/app-tier/ app-tier --recursive
cd ~/app-tier
npm install
pm2 start index.js
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Check if App is Running 

pm2 list
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If the status is errored, check logs:

pm2 logs
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Enable Auto-Start for PM2 

pm2 startup
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Copy the exact command from the output and run it.

Save the PM2 process list:

pm2 save
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Test App Tier

Health Check Endpoint 

curl http://localhost:4000/health
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Expected response:

"This is the health check"
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Database Connection Test 

curl http://localhost:4000/transaction
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Expected response:

{"result":[{"id":1,"amount":400,"description":"groceries"}]}
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If both tests pass, the app layer is configured correctly.

Conclusion

This completes the App Tier setup for our AWS Three-Tier Architecture.

➡️ Proceed to Part 5 to continue the implementation:

Continue to the next Part AWS Three-Tier Architecture (Part-5)

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