What Is Elastic Load Balance?
Elastic Load Balance (ELB) automatically distributes incoming traffic across multiple backend servers based on the listening rules you configure. ELB expands service capabilities of applications and eliminates single points of failure (SPOFs), improving application availability.
A load balancer distributes incoming traffic across multiple backend servers that reside in one or more availability zones (AZs).
- Listener: You can add one or more listeners to a load balancer. A listener uses the protocol and port you specify to check for requests from clients and route the requests to associated backend servers based on the listening rules you define.
- Backend server group: A backend server group routes requests to one or more backend servers.
You can configure health checks for each backend server group to check the running status of each backend server. When the health check result of a backend server is Unhealthy, the load balancer automatically stops routing new requests to this server until it recovers.
Load Balancer Type
ELB provides two types of load balancers: classic load balancers and shared load balancers.
- Classic load balancer: This type of load balancer can well handle web services with low traffic and simple applications.
- Shared load balancer: Shared load balancers are renamed from enhanced load balancers. They are suitable for web services with high access traffic. Requests are forwarded based on domain names or URLs, making request routing more flexible.
For more information, see Differences Between Classic and Shared Load Balancers.
Currently, classic load balancers are supported only in regions in the Latin America.
Access to ELB
You can use either of the following methods to access ELB:
- Management console
You can make calls to APIs to access ELB. For details, see the Elastic Load Balance API Reference.