Last Updated: Dec 22, 2017

Welcome to use Alibaba Cloud Server Load Balancer. The Server Load Balancer virtualizes multiple Elastic Compute Services (ECSs) in a region as a high-performance and high-availability application service pool by setting a virtual service address (an IP address). With a method specified by the applications, the requests from a client on the network are distributed to the ECS pool. Alibaba Cloud Server Load Balancer checks an ECS for health in the ECS pool and isolates it from an abnormal ECS, therefore troubleshooting a faulty node of an ECS and improving the overall service capability of applications. In addition to the standard Server Load Balancer functions, the Server Load Balancer features anti-DDoS attacks by TCP and HTTP to enhance the protective capability of an application server. Alibaba Cloud Server Load Balancer is a supporting service of the ECS for multiple machines, and needs to operate with the ECS.

Before using these interfaces, fully learn about the description, access protocol, and charging mode of the Server Load Balancer.

API conceptual diagram

  • Alibaba Cloud Server Load Balancer API involves three basic concepts.
    1. LoadBalancer indicates a Server Load Balancer instance.
    2. Listener indicates the customized Server Load Balancer policies and forwarding rules.
    3. BackendServer is a group of backend ECSs.

An external request for access is distributed by a Server Load Balancer instance to the backend ECS for processing in accordance with relevant policies and forwarding rules.


Term Full name English Description
Server Load Balancer Server Load Balancer The server load balancer is referred to as the Server Load Balancer. A network server load balancer provided by Alibaba Cloud. It can provide users with the ECS instance-based TCP and HTTP server load balancer service in combination with Alibaba Cloud ECS.
Region Region Indicates the region where resources reside. One region involves a group of data centers.
LoadBalancer Load Balancer The server load balancer instance is referred to as the Server Load Balancer instance. A Server Load Balancer instance indicates an operating instance in the Server Load Balancer service. To use the Server Load Balancer service, a user must create a Server Load Balancer instance. LoadBalancerId uniquely identifies the Server Load Balancer instance of the user.
Listener Listener Server Load Balancer listener. A Server Load Balancer listener includes listener ports, Server Load Balancer policies and health check configuration.
BackendServer Backend Server Backend server. A group of ECSs receiving the Server Load Balancer-distributed requests. The Server Load Balancer forwards the external requests for access to this group of backend servers for processing in accordance with user-defined rules.

Business restrictions and resource specification restrictions

Alibaba Cloud Server Load Balancer restricts the number of Server Load Balancer instances and listeners on instances for each user. It also restricts all the parameters concerning instance specifications, bandwidth ranges, and health checks. Before using the Server Load Balancer API, read the latest business restriction rules and resource specification restrictions on Limitations.

If any optional value and availability of a parameter conflicts with those in the resource specification restrictions on the official website, the value and availability on the official website prevail.

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