Name

ngx_http_upstream_vnswrr_module.

Introduction

The VNSWRR module is an efficient load balancing algorithm that is smooth, decentralized, and high-performance compared to Nginx's official SWRR algorithm.

Example

http {

    upstream backend {
        vnswrr; # enable VNSWRR load balancing algorithm.
        127.0.0.1 port=81;
        127.0.0.1 port=82 weight=2;
        127.0.0.1 port=83;
        127.0.0.1 port=84 backup;
        127.0.0.1 port=85 down;
    }
    
    server {
        server_name localhost;
        
        location / {
            proxy_pass http://backend;
        }
    }
}

Installation

Build Tengine with this module from source:

./configure --add-module=./modules/ngx_http_upstream_vnswrr_module/
make
make install

Directive

vnswrr

Syntax: vnswrr
Default: none
Context: upstream

Enable vnswrr load balancing algorithm.

Performance

In the same pressure environment (wrk, 500 concurrency, keepalive, 2000 endpoint), the CPU consumption of VNSWRR algorithm accounts for 0.27% ( ngx_http_upstream_get_vnswrr).
Compared with VNSWRR algorithm, the CPU consumption of SWRR (ngx_http_upstream_get_peer 39%) is an order of magnitude higher than VNSWRR.

In the above environment, the QPS of VNSWRR increases by 60% compared with SWRR algorithm.

Observing the changes of QPS and RT in the different back-end number scenarios.
Under SWRR algorithm, when the number of back-end for every 500 addition, then the QPS of Nginx decreases by about 10% and RT increases by about 1 ms. But under the VNSWRR algorithm, QPS and RT do not change much.