What is Load Balancing in AWS?

Published Sep 16, 2024

What is Load Balancing?

Load balancing is the process of distributing incoming network traffic across multiple servers to ensure no single server becomes overwhelmed, thereby improving the availability and responsiveness of applications. Load balancers help to:

Distribute Traffic: Spread incoming traffic across multiple servers.
Ensure High Availability: Improve application availability by rerouting traffic in case of server failure.
Enhance Performance: Optimize resource utilization and reduce latency by balancing the load.
Increase Fault Tolerance: Automatically detect and handle server failures.

Types of Load Balancing

Application Load Balancing (Layer 7): Operates at the application layer (HTTP/HTTPS) and can make routing decisions based on the content of the request.
Network Load Balancing (Layer 4): Operates at the transport layer (TCP/UDP) and routes traffic based on IP address and port.

Load Balancing in AWS

AWS offers a variety of load balancing services under the Elastic Load Balancing (ELB) umbrella, including:

Application Load Balancer (ALB): Best suited for HTTP and HTTPS traffic, offering advanced routing, SSL termination, and WebSocket support.
Network Load Balancer (NLB): Best suited for TCP and UDP traffic, capable of handling millions of requests per second with ultra-low latency.
Classic Load Balancer (CLB): Supports both Layer 4 and Layer 7 load balancing but is considered legacy compared to ALB and NLB.

Benefits of AWS Load Balancers

Scalability: Automatically adjusts capacity to handle changes in traffic.
Security: Integrates with AWS services like AWS Shield, AWS WAF, and AWS Certificate Manager.
Availability: Distributes traffic across multiple Availability Zones.
Flexibility: Supports different types of traffic and advanced routing features.

How to Implement Load Balancing in AWS

Step 1: Create an Application Load Balancer (ALB)

1.1 Log in to the AWS Management Console

Navigate to the EC2 Dashboard and click on "Load Balancers" under the "Load Balancing" section.

1.2 Click "Create Load Balancer"

Choose "Application Load Balancer" and click "Create".

1.3 Configure Load Balancer

Name: Enter a name for your load balancer.
Scheme: Choose "Internet-facing" or "Internal" based on your needs.
IP address type: Choose "ipv4" or "dualstack" for IPv6 support.
Listeners: Select the protocols and ports for your listener (e.g., HTTP and/or HTTPS).
Availability Zones: Select the VPC and the subnets (Availability Zones) where the load balancer will route traffic.

1.4 Configure Security Settings (for HTTPS)

If you chose HTTPS, configure SSL settings:

Select Certificate: Use AWS Certificate Manager (ACM) to request or import a certificate.
Security Policy: Choose an SSL security policy.

1.5 Configure Security Groups

Select or create security groups that allow traffic on the necessary ports (e.g., HTTP/HTTPS).

1.6 Configure Routing

Target Group: Create a new target group or select an existing one.
Target Type: Choose between "Instances", "IP addresses", or "Lambda function".
Health Checks: Configure health check settings to monitor the health of targets.

1.7 Register Targets

Add the instances or IP addresses that will receive traffic from the load balancer.

1.8 Review and Create

Review your settings and click "Create".

Example: Creating an ALB using AWS CLI

aws elbv2 create-load-balancer \

    --name my-load-balancer \

    --subnets subnet-12345678 subnet-87654321 \

    --security-groups sg-0123456789abcdef0 \

    --scheme internet-facing \

    --type application  

aws elbv2 create-target-group \

    --name my-targets \

    --protocol HTTP \

    --port 80 \

    --vpc-id vpc-0123456789abcdef0 \

    --health-check-protocol HTTP \

    --health-check-path /index.html \

    --matcher HttpCode=200

 aws elbv2 register-targets \

    --target-group-arn arn:aws:elasticloadbalancing:region:account-id:targetgroup/my-targets/0123456789abcdef \

    --targets Id=i-0123456789abcdef0 Id=i-0abcdef1234567890

 aws elbv2 create-listener \

    --load-balancer-arn arn:aws:elasticloadbalancing:region:account-id:loadbalancer/app/my-load-balancer/0123456789abcdef \

    --protocol HTTP \

    --port 80 \

    --default-actions Type=forward,TargetGroupArn=arn:aws:elasticloadbalancing:region:account-id:targetgroup/my-targets/0123456789abcdef

Step 2: Create a Network Load Balancer (NLB)

2.1 Log in to the AWS Management Console

Navigate to the EC2 Dashboard and click on "Load Balancers" under the "Load Balancing" section.

2.2 Click "Create Load Balancer"

Choose "Network Load Balancer" and click "Create".

2.3 Configure Load Balancer

Name: Enter a name for your load balancer.
Scheme: Choose "Internet-facing" or "Internal".
Listeners: Select the protocols and ports for your listener (e.g., TCP).

2.4 Configure Availability Zones

Select the VPC and the subnets (Availability Zones) where the load balancer will route traffic.

2.5 Configure Security Groups (Optional)

NLBs do not require security groups, but you can associate one if needed for backend security.

2.6 Configure Target Groups

Target Group: Create a new target group or select an existing one.
Target Type: Choose between "Instances", "IP addresses", or "Lambda function".
Health Checks: Configure health check settings to monitor the health of targets.

2.7 Register Targets

Add the instances or IP addresses that will receive traffic from the load balancer.

2.8 Review and Create

Review your settings and click "Create".

Example: Creating an NLB using AWS CLI

bash

aws elbv2 create-load-balancer \

    --name my-nlb \

    --subnets subnet-12345678 subnet-87654321 \

    --scheme internet-facing \

    --type network

 aws elbv2 create-target-group \

    --name my-nlb-targets \

    --protocol TCP \

    --port 80 \

    --vpc-id vpc-0123456789abcdef0 \

    --health-check-protocol TCP

 aws elbv2 register-targets \

    --target-group-arn arn:aws:elasticloadbalancing:region:account-id:targetgroup/my-nlb-targets/0123456789abcdef \

    --targets Id=i-0123456789abcdef0 Id=i-0abcdef1234567890

 aws elbv2 create-listener \

    --load-balancer-arn arn:aws:elasticloadbalancing:region:account-id:loadbalancer/net/my-nlb/0123456789abcdef \

    --protocol TCP \

    --port 80 \

    --default-actions Type=forward,TargetGroupArn=arn:aws:elasticloadbalancing:region:account-id:targetgroup/my-nlb-targets/0123456789abcdef

Monitoring and Managing Load Balancers

Using Amazon CloudWatch

Metrics: Monitor load balancer metrics such as request count, latency, and healthy host count.
Alarms: Set up CloudWatch Alarms to notify you of unusual activity or performance issues.

Using AWS CloudTrail

Logging: Enable CloudTrail to log API activity related to your load balancer, providing visibility into actions taken on your load balancer.

Best Practices for Load Balancing

Distribute Traffic: Use multiple Availability Zones to ensure high availability and fault tolerance.
Secure Your Traffic: Use SSL/TLS termination on the load balancer to encrypt traffic.
Optimize Health Checks: Configure health checks to ensure only healthy instances receive traffic.
Monitor Performance: Regularly monitor load balancer metrics and set up alerts for potential issues.
Regularly Update Security Groups: Ensure security groups are correctly configured to allow necessary traffic while blocking potential threats.

Load balancing is a crucial component for ensuring the availability, performance, and reliability of your applications. AWS provides robust load balancing solutions through Elastic Load Balancing (ALB, NLB, and CLB) to cater to different needs. By following the steps and best practices outlined in this guide, you can effectively implement and manage load balancing in AWS, ensuring your applications are resilient and scalable.