Nginx负载均衡中的fair算法原理与实现

Http {
    upstream backend {
        fair;
        server backend1.example.com weight=3;
        server backend2.example.com weight=2;
        server backend3.example.com weight=1;
    }

    server {
        listen 80;
        server_name example.com;

        location / {
            proxy_pass http://backend;
        }
    }
}

import math

servers = [
    {'name': 'backend1.example.com', 'weight': 3},
    {'name': 'backend2.example.com', 'weight': 2},
    {'name': 'backend3.example.com', 'weight': 1},
]

total_weight = sum(server['weight'] for server in servers)
GCd = math.gcd(*[server['weight'] for server in servers])

for server in servers:
    server['current_weight'] = server['weight']
    
while True:
    best_server = None
    best_weight = 0
    
    for server in servers:
        server['current_weight'] += server['weight']
        if server['current_weight'] > best_weight:
            best_server = server
            best_weight = server['current_weight']
    
    best_server['current_weight'] -= total_weight
    
    print('Request sent to: %s' % best_server['name'])