Nginx 反向代理与负载均衡：upstream 与 proxy_pass 实战

# 不带 URI：保留完整原始 URI 转发
location /api/ {
    proxy_pass http://backend;               # 请求 /api/user → http://backend/api/user
}

# 带 URI：替换匹配部分
location /api/ {
    proxy_pass http://backend/;              # 请求 /api/user → http://backend/user
}

location /api/ {
    proxy_pass http://backend/v2;            # 请求 /api/user → http://backend/v2/user
}

location / {
    proxy_pass http://backend;
    proxy_http_version 1.1;
    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;
}

upstream backend {
    server 10.0.0.11:8080;
    server 10.0.0.12:8080;
    server 10.0.0.13:8080;
}

upstream backend {
    least_conn;                              # 最少连接
    server 10.0.0.11:8080 weight=3;          # 权重 3
    server 10.0.0.12:8080 weight=1;          # 权重 1
    server 10.0.0.13:8080 down;              # 手动摘除
}

upstream backend {
    ip_hash;                                 # 同一客户端 IP 会话保持
    server 10.0.0.11:8080;
    server 10.0.0.12:8080;
}

upstream cache_backend {
    hash $request_uri consistent;            # 一致性哈希，节点增减影响最小
    server 10.0.0.21:9001;
    server 10.0.0.22:9001;
    server 10.0.0.23:9001;
}

upstream backend {
    server 10.0.0.11:8080 max_fails=3 fail_timeout=30s;
    server 10.0.0.12:8080 max_fails=3 fail_timeout=30s;
}

upstream backend {
    server 10.0.0.11:8080;
    server 10.0.0.12:8080;
    server 10.0.0.99:8080 backup;           # 备用节点
}

# 每 5 秒探测后端，失败则用 upstream_conf 动态下掉
curl -fsS http://10.0.0.11:8080/health || \
  echo "server 10.0.0.11:8080 down;" | nginx -s reload

location / {
    proxy_connect_timeout   5s;      # 建立上游连接超时
    proxy_send_timeout      10s;     # 发送请求体超时
    proxy_read_timeout      30s;     # 读取上游响应超时
}

location / {
    proxy_next_upstream error timeout invalid_header http_502 http_503;
    proxy_next_upstream_tries 3;          # 最多尝试 3 个后端
    proxy_next_upstream_timeout 5s;       # 总重试窗口
}

location /ws/ {
    proxy_pass http://ws_backend;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_read_timeout 3600s;          # 长连接读超时拉长
}

upstream backend {
    server 10.0.0.11:8080;
    keepalive 32;                      # 与上游保持 32 个空闲连接
}

location / {
    proxy_pass http://backend;
    proxy_http_version 1.1;            # 复用连接必须 HTTP/1.1
    proxy_set_header Connection "";    # 清空默认 Connection 头
}

location / {
    resolver 10.0.0.53 valid=30s;      # 指定 DNS 与缓存时间
    proxy_pass http://backend.service.consul:8080;
}

upstream backend {
    server 10.0.0.11:8080;
    server 10.0.0.12:8080;
}

# 通过 njs 或 Lua 在请求期按 key 选择后端
location /canary/ {
    set $backend http://10.0.0.11:8080;
    if ($cookie_canary = "new") {
        set $backend http://10.0.0.12:8080;
    }
    proxy_pass $backend;               # 变量型 proxy_pass 支持灰度分流
}

# conf.d/proxy_params.conf
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 5s;
proxy_read_timeout 60s;
proxy_http_version 1.1;

server {
    location /api/ {
        include proxy_params;
        proxy_pass http://backend;
    }
}

upstream backend {
    server 10.0.0.11:8080;                     # 稳定版
    server 10.0.0.12:8080 weight=9;            # 稳定版主流量
    server 10.0.0.13:8080 weight=1;            # 新版灰度 10%
}