Basic Architecture

BLB offers load balancing services via clusters. If a server in the load balancing system cluster encounters failure, other servers automatically take over its tasks to ensure high service availability. The basic architecture of BLB is as follows:

This document takes a TCP listener as an example to illustrate the processing flow of an access request:

1. When a user sends a request, he/she initiates a TCP handshake request to the listener address and port of the service;
2. In Layer 4 Load Balancing, the addresses of all user-configured real cloud servers are identified. Using configured load balancing strategies (e.g., weighted round-robin, weighted least connections, source IP), an available cloud server is selected to initiate a TCP handshake request.
3. After a successful connection is established, a mapping transformation is performed between connections, and frontend requests are forwarded to various cloud servers. During BLB operation, the Layer 4 Load Balancer continuously performs health checks on each cloud server according to configurations and filters out any unavailable servers.

This document takes a HTTP listener as an example to illustrate the processing flow of an access request:

1. When a user sends a request, he/she initiates a TCP handshake request to the listener address and port of the service;
2. The Layer 4 Load Balancer directly forwards user requests to the Layer 7 Load Balancer, which then initiates a TCP handshake with a real cloud server. In addition to fully supporting Layer 4 functionality, the Layer 7 Load Balancer offers features such as retrieving real IPs, identifying listener protocols, enabling session persistence, enabling HTTPS redirection, customizing configurations, and more.
3. After a successful connection is established, a mapping transformation is performed between connections, and frontend requests are forwarded to various cloud servers. Throughout BLB operations, the Layer 7 Load Balancer continually performs health checks on each cloud server according to configurations, filtering out any unavailable servers.