搭建负载均衡

本节介绍如何使用Nginx搭建负载均衡。

基本配置

轮询

upstream backend {
    server 192.168.1.10:8080;
    server 192.168.1.11:8080;
    server 192.168.1.12:8080;
}

server {
    listen 80;
    server_name lb.example.com;

    location / {
        proxy_pass http://backend;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

负载均衡算法

最少连接

upstream backend {
    least_conn;
    server 192.168.1.10:8080;
    server 192.168.1.11:8080;
    server 192.168.1.12:8080;
}

IP Hash

upstream backend {
    ip_hash;
    server 192.168.1.10:8080;
    server 192.168.1.11:8080;
    server 192.168.1.12:8080;
}

加权轮询

upstream backend {
    server 192.168.1.10:8080 weight=3;
    server 192.168.1.11:8080 weight=2;
    server 192.168.1.12:8080 weight=1;
}

健康检查

基本健康检查

upstream backend {
    server 192.168.1.10:8080 max_fails=3 fail_timeout=30s;
    server 192.168.1.11:8080 max_fails=3 fail_timeout=30s;
    server 192.168.1.12:8080 max_fails=3 fail_timeout=30s;
}

备用服务器

upstream backend {
    server 192.168.1.10:8080;
    server 192.168.1.11:8080;
    server 192.168.1.12:8080 backup;
}

会话保持

IP Hash

upstream backend {
    ip_hash;
    server 192.168.1.10:8080;
    server 192.168.1.11:8080;
    server 192.168.1.12:8080;
}

Sticky Cookie

upstream backend {
    sticky cookie srv_id expires=1h domain=.example.com path=/;
    server 192.168.1.10:8080;
    server 192.168.1.11:8080;
    server 192.168.1.12:8080;
}

完整示例

生产环境配置

upstream backend {
    least_conn;
    server 192.168.1.10:8080 weight=3 max_fails=3 fail_timeout=30s;
    server 192.168.1.11:8080 weight=2 max_fails=3 fail_timeout=30s;
    server 192.168.1.12:8080 weight=1 max_fails=3 fail_timeout=30s;
    server 192.168.1.13:8080 backup;
}

proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=proxy_cache:10m max_size=1g inactive=60m;

server {
    listen 80;
    server_name lb.example.com;

    location / {
        proxy_cache proxy_cache;
        proxy_cache_valid 200 60m;
        proxy_cache_key "$scheme$request_method$host$request_uri";
        proxy_pass http://backend;

        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;

        proxy_connect_timeout 60;
        proxy_send_timeout 60;
        proxy_read_timeout 60;

        proxy_buffering on;
        proxy_buffer_size 4k;
        proxy_buffers 8 4k;
        proxy_busy_buffers_size 8k;

        add_header X-Cache-Status $upstream_cache_status;
    }

    location /health {
        access_log off;
        return 200 "healthy\n";
        add_header Content-Type text/plain;
    }
}

监控

查看负载均衡状态

location /nginx_status {
    stub_status on;
    access_log off;
    allow 127.0.0.1;
    deny all;
}

查看后端服务器状态

curl http://lb.example.com/health

总结

搭建负载均衡的关键点：

• 负载均衡算法：轮询、最少连接、IP Hash、加权轮询
• 健康检查：max_fails、fail_timeout
• 备用服务器：backup
• 会话保持：IP Hash、Sticky Cookie
• 监控：nginx_status、health检查

使用Nginx搭建负载均衡，实现高可用和高性能。