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Nginx 负载均衡

负载均衡是Nginx的重要功能之一，可以将客户端请求分发到多个后端服务器，提高应用的可用性和性能。

负载均衡算法

轮询(Round Robin)

默认算法，按时间顺序逐一分配请求：

upstream backend {
    server backend1.example.com;
    server backend2.example.com;
    server backend3.example.com;
}

加权轮询(Weighted Round Robin)

根据权重分配请求，权重高的服务器处理更多请求：

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

IP哈希(IP Hash)

根据客户端IP地址的哈希值分配请求，确保同一IP的请求总是发送到同一服务器：

upstream backend {
    ip_hash;
    server backend1.example.com;
    server backend2.example.com;
    server backend3.example.com;
}

最少连接(Least Connections)

将请求分配给当前连接数最少的服务器：

upstream backend {
    least_conn;
    server backend1.example.com;
    server backend2.example.com;
    server backend3.example.com;
}

法定URL哈希(Consistent Hash)

根据URL的哈希值分配请求：

upstream backend {
    hash $request_uri consistent;
    server backend1.example.com;
    server backend2.example.com;
    server backend3.example.com;
}

健康检查配置

基本健康检查参数 

upstream backend {
    server backend1.example.com max_fails=3 fail_timeout=30s;
    server backend2.example.com max_fails=3 fail_timeout=30s;
    server backend3.example.com max_fails=3 fail_timeout=30s;
}

参数说明：

  • max_fails: 在fail_timeout时间内允许的最大失败次数
  • fail_timeout: 服务器被标记为失败后的等待时间

备用服务器配置 

upstream backend {
    server backend1.example.com;
    server backend2.example.com;
    server backup.example.com backup;
}

高级负载均衡配置

服务器权重调整 

upstream backend {
    server backend1.example.com weight=5;
    server backend2.example.com weight=3;
    server backend3.example.com weight=2;
}

服务器最大连接数限制 

upstream backend {
    server backend1.example.com max_conns=1000;
    server backend2.example.com max_conns=1000;
}

连接池配置 

upstream backend {
    server backend1.example.com;
    server backend2.example.com;
    
    # 保持到上游服务器的连接
    keepalive 32;
    keepalive_requests 100;
    keepalive_timeout 60s;
}

HTTP负载均衡完整示例 

upstream app_servers {
    # 使用最少连接算法
    least_conn;
    
    # 配置后端服务器
    server app1.example.com:8080 weight=3 max_fails=2 fail_timeout=30s;
    server app2.example.com:8080 weight=2 max_fails=2 fail_timeout=30s;
    server app3.example.com:8080 weight=1 max_fails=2 fail_timeout=30s;
    
    # 备用服务器
    server backup.example.com:8080 backup;
    
    # 保持连接
    keepalive 16;
}

server {
    listen 80;
    server_name example.com;
    
    location / {
        proxy_pass http://app_servers;
        
        # 代理设置
        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;
        
        # 连接超时设置
        proxy_connect_timeout 60s;
        proxy_send_timeout 60s;
        proxy_read_timeout 60s;
    }
    
    # 健康检查端点
    location /health {
        access_log off;
        return 200 "healthy\n";
        add_header Content-Type text/plain;
    }
}

TCP/UDP负载均衡

TCP负载均衡 

stream {
    upstream mysql_backend {
        server mysql1.example.com:3306 max_fails=2 fail_timeout=30s;
        server mysql2.example.com:3306 max_fails=2 fail_timeout=30s;
    }
    
    server {
        listen 3306;
        proxy_pass mysql_backend;
        proxy_timeout 1s;
        proxy_responses 1;
        proxy_connect_timeout 1s;
    }
}

UDP负载均衡 

stream {
    upstream dns_backend {
        server dns1.example.com:53 max_fails=2 fail_timeout=30s;
        server dns2.example.com:53 max_fails=2 fail_timeout=30s;
    }
    
    server {
        listen 53 udp;
        proxy_pass dns_backend;
        proxy_timeout 1s;
        proxy_responses 1;
        proxy_connect_timeout 1s;
    }
}

会话持久化

基于Cookie的会话持久化 

upstream backend {
    ip_hash;  # 确保同一客户端请求发送到同一服务器
    server backend1.example.com;
    server backend2.example.com;
}

server {
    location / {
        proxy_pass http://backend;
        
        # 传递会话信息
        proxy_pass_header Set-Cookie;
        proxy_set_header Cookie $http_cookie;
    }
}

使用sticky模块(需要第三方模块) 

upstream backend {
    server backend1.example.com;
    server backend2.example.com;
    
    sticky cookie affinity:serverid maxage=30000 httponly;
}

负载均衡监控

启用状态监控 

upstream backend {
    server backend1.example.com;
    server backend2.example.com;
    server backend3.example.com;
    
    # 启用状态监控
    zone backend_zone 64k;
}

server {
    listen 80;
    
    # 状态页面
    location /status {
        upstream_conf;
    }
}

使用第三方监控模块 

# 需要安装nginx-module-vts模块
vhost_traffic_status_zone;

server {
    listen 80;
    server_name example.com;
    
    location /status {
        vhost_traffic_status_display;
        vhost_traffic_status_display_format html;
    }
}

故障转移配置

主备模式 

upstream primary_backup {
    server primary.example.com max_fails=2 fail_timeout=10s;
    server backup.example.com backup;
}

多级故障转移 

upstream multi_tier {
    server tier1a.example.com max_fails=1 fail_timeout=10s;
    server tier1b.example.com max_fails=1 fail_timeout=10s;
    server tier2.example.com backup max_fails=1 fail_timeout=10s;
    server emergency.example.com backup;
}

性能优化

连接优化 

upstream backend {
    server backend1.example.com:8080;
    server backend2.example.com:8080;
    
    # 保持连接到后端服务器
    keepalive 32;
    keepalive_requests 100;
    keepalive_timeout 60s;
    
    # 负载均衡算法
    least_time last_byte;
}

响应头处理 

location / {
    proxy_pass http://backend;
    
    # 移除后端服务器的Server头
    proxy_hide_header Server;
    
    # 添加负载均衡标识
    add_header X-Upstream-Server $upstream_addr always;
    add_header X-Proxy-Server $hostname always;
}

完整生产环境负载均衡配置 

# HTTP负载均衡
upstream app_cluster {
    # 使用最少连接算法
    least_conn;
    
    # 主服务器组
    server app1.example.com:8080 weight=4 max_fails=2 fail_timeout=30s max_conns=1000;
    server app2.example.com:8080 weight=4 max_fails=2 fail_timeout=30s max_conns=1000;
    server app3.example.com:8080 weight=2 max_fails=2 fail_timeout=30s max_conns=1000;
    
    # 备用服务器
    server app4.example.com:8080 backup;
    
    # 保持连接
    keepalive 32;
    keepalive_requests 1000;
    keepalive_timeout 60s;
    
    # 共享内存区用于状态统计
    zone app_cluster 256k;
}

# SSL终止负载均衡器
server {
    listen 443 ssl http2;
    server_name example.com;
    
    # SSL配置
    ssl_certificate /path/to/certificate.crt;
    ssl_certificate_key /path/to/private.key;
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384;
    
    # 安全头
    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-Content-Type-Options "nosniff" always;
    
    location / {
        proxy_pass http://app_cluster;
        
        # 代理头设置
        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_set_header X-Original-URI $request_uri;
        
        # 超时设置
        proxy_connect_timeout 60s;
        proxy_send_timeout 60s;
        proxy_read_timeout 60s;
        
        # 缓冲设置
        proxy_buffer_size 4k;
        proxy_buffers 8 4k;
        proxy_busy_buffers_size 8k;
    }
    
    # 健康检查
    location /health {
        access_log off;
        return 200 "healthy\n";
        add_header Content-Type text/plain;
    }
    
    # 状态监控
    location /nginx_status {
        stub_status on;
        access_log off;
        allow 127.0.0.1;
        allow 10.0.0.0/8;
        deny all;
    }
}

通过合理配置负载均衡，可以有效提高应用的可用性、性能和可扩展性。