Elastic Load Balancer (ELB) and Auto Scaling Group are two important services provided by AWS that help ensure high availability, scalability, and fault tolerance for applications running on Amazon Elastic Compute Cloud (EC2). Here’s an overview of each:
- Elastic Load Balancer (ELB)
- Elastic Load Balancer is a managed load balancing service that automatically distributes incoming application traffic across multiple EC2 instances or IP addresses.
- ELB helps improve the availability and fault tolerance of applications by distributing traffic evenly across healthy instances, thus preventing any single instance from becoming overwhelmed.
- ELB supports various types of load balancers, including Application Load Balancer (ALB), Network Load Balancer (NLB), and Classic Load Balancer (CLB), each tailored for specific use cases and traffic types.
- Key features of ELB include health checks to monitor the health of instances, SSL termination for encrypting traffic, and integration with other AWS services like Auto Scaling and AWS Certificate Manager.
- ELB automatically scales to handle incoming traffic and can scale both vertically (by upgrading load balancer resources) and horizontally (by adding more instances to the load balancer).
- Auto Scaling Group
- Auto Scaling Group (ASG) is a service that automatically adjusts the number of EC2 instances in a group based on predefined scaling policies and conditions.
- ASG helps ensure that the desired number of instances are available to handle incoming traffic, even during peak loads or sudden spikes in demand.
- You define minimum, maximum, and desired capacities for your Auto Scaling Group, along with scaling policies that dictate when and how instances should be added or removed based on metrics such as CPU utilization, network traffic, or custom CloudWatch metrics.
- ASG integrates with ELB to automatically register and deregister instances from the load balancer as they are launched or terminated, ensuring that traffic is evenly distributed across healthy instances.
- ASG can launch instances from pre-configured Amazon Machine Images (AMIs), allowing you to specify the configuration, including instance type, storage, security groups, and user data scripts.
- ASG works seamlessly with other AWS services, such as CloudWatch for monitoring and scaling based on custom metrics, and AWS Lambda for executing custom actions in response to scaling events.
Together, Elastic Load Balancer and Auto Scaling Group form a powerful combination for achieving high availability, scalability, and fault tolerance for applications running on AWS infrastructure. ELB distributes incoming traffic across multiple instances, while ASG dynamically adjusts the number of instances based on workload demand, ensuring optimal performance and resource utilization.