2.4.3. Elastic Load Balancing (ELB)
š” First Principle: Elastic Load Balancing (ELB) automatically distributes incoming application traffic across multiple healthy targets, ensuring high availability, fault tolerance, and optimal resource utilization.
ELB is a service that automatically distributes incoming application traffic across multiple targets, such as EC2 instances, containers, Lambda functions, and IP addresses. It's crucial for building scalable and highly available applications.
Key Characteristics of ELB:
- Traffic Distribution: Spreads incoming requests across healthy targets, preventing any single target from becoming a bottleneck.
- Health Checks: Continuously monitors the health of registered targets. If a target fails a configured number of health checks, ELB automatically takes it out of rotation and stops sending traffic to it.
- Automatic Scaling: ELB automatically scales its own capacity to handle fluctuations in incoming application traffic.
- Cross-AZ Load Balancing: Distributes traffic across all registered targets in all enabled Availability Zones (AZs), even if an AZ experiences issues, ensuring continuous operation.
- Multiple Load Balancer Types:
- Application Load Balancer (ALB): Operates at Layer 7 (HTTP/HTTPS traffic). Best for web applications, offers advanced routing (e.g., path-based, host-based).
- Network Load Balancer (NLB): Operates at Layer 4 (TCP/UDP traffic). Designed for extreme performance and static IP addresses.
- Gateway Load Balancer (GLB): For deploying and managing virtual appliances (e.g., firewalls).
Scenario: A company needs to distribute incoming web traffic across multiple EC2 instances for scalability and ensure that if an instance becomes unhealthy, traffic is automatically routed away from it.
Reflection Question: How does Elastic Load Balancing (ELB), with its efficient traffic distribution and continuous health checks, fundamentally ensure high availability, fault tolerance, and optimal resource utilization for your applications?