What is ELB?

Elastic Load Balancer (ELB) is a key service provided by Amazon Web Services (AWS) that allows you to distribute incoming traffic across multiple instances or targets, improving the availability, scalability, and fault tolerance of your applications. In this article, we will explore how ELB works and its key components.

At a high level, ELB works by receiving traffic from clients and routing it to one or more backend instances or targets based on predefined rules. ELB can handle millions of requests per second and distribute them evenly across backend resources, helping to prevent overloading and reducing response times.

Image Credit: AWS Docs

Key components of ELB:

Load balancer: This is the core component of ELB, responsible for receiving incoming traffic from clients and distributing it across backend instances or targets. There are three types of load balancers: classic, application, and network.

Target groups: A target group is a logical grouping of backend resources that receive traffic from the load balancer. Target groups are associated with a specific listener and can be added or removed dynamically.

Health checks: ELB performs periodic health checks on backend resources to ensure that they are healthy and can handle incoming traffic. If a resource fails a health check, ELB can automatically remove it from the target group and route traffic to other healthy resources.

Listener: A listener is a process that listens for incoming traffic on a specific port and protocol. Each listener is associated with a specific load balancer and can have one or more rules that define how incoming traffic is routed to target groups.

SSL/TLS certificates: ELB can terminate SSL/TLS traffic at the load balancer, reducing the processing overhead on backend resources. You can upload your own SSL/TLS certificates to ELB or use certificates provided by AWS Certificate Manager (ACM).

Security groups: ELB uses security groups to control incoming and outgoing traffic. You can configure security groups to allow or deny traffic from specific IP addresses or networks.

In order to use ELB, you need to follow a few steps:

Create a load balancer: You can create a load balancer using the AWS Management Console, the AWS Command Line Interface (CLI), or the AWS SDKs. You can choose the type of load balancer you want to create, the availability zones in which it will be deployed, and the protocols and ports it will use.

Configure target groups: You can create target groups using the same tools as load balancers. You can add instances, IP addresses, or Lambda functions to target groups, and configure health checks to ensure that they are healthy.

Configure listeners: You can create listeners using the same tools as load balancers. You can define rules that specify how traffic is routed to target groups based on factors such as URL path, query string, and host header.

Associate target groups with listeners: You can associate target groups with listeners using the AWS Management Console or the CLI. You can add or remove target groups dynamically, depending on the traffic load.

Summary:

ELB is a key service provided by AWS that allows you to distribute incoming traffic across multiple backend resources, improving the availability, scalability, and fault tolerance of your applications. The key components of ELB include load balancers, target groups, health checks, listeners, SSL/TLS certificates, and security groups. By following a few simple steps, you can configure ELB to handle millions of requests per second and improve the performance and reliability of your applications.