《Nginx缓存策略优化：命中失效与过期时间配置》

http {
    # 加载purge模块（编译时需添加--with-http_cache_purge_module）
    load_module modules/ngx_http_cache_purge_module.so;

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

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

        # 开启缓存
        proxy_cache my_cache;
        proxy_cache_key "$host$request_uri";
        proxy_cache_valid 200 302 10m;

        # 配置purge缓存的接口
        location ~ /purge(/.*) {
            proxy_cache_purge my_cache "$host$1";
            return 200 "Cache purged: $host$1";
        }

        # 反向代理后端服务
        location / {
            proxy_pass http://backend_server;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
        }
    }
}

# 200/302响应缓存10分钟，301永久缓存1天，404/500错误缓存1分钟
proxy_cache_valid 200 302 10m;
proxy_cache_valid 301 1d;
proxy_cache_valid 404 500 1m;

http {
    # 定义map，根据请求路径匹配不同TTL
    map $request_uri $cache_ttl {
        default 10m;
        ~^/api/article 30m;
        ~^/api/order 1m;
        ~^/static 1h;
    }

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

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

        proxy_cache my_cache;
        proxy_cache_key "$host$request_uri";
        # 动态使用map中的TTL
        proxy_cache_valid $cache_ttl;
    }
}

# 优先使用后端响应的Cache-Control头，未指定则默认10分钟
proxy_cache_use_stale updating;
proxy_ignore_headers Cache-Control Expires;
proxy_set_header Cache-Control $upstream_http_cache_control;
proxy_cache_valid 10m;

user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;

events {
    worker_connections 10240;
    use epoll;
    multi_accept on;
}

http {
    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    # 日志格式：记录缓存命中状态（$upstream_cache_status）
    log_format main '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" '
                    '"$http_user_agent" "$upstream_cache_status"';

    access_log /var/log/nginx/access.log main;

    # 配置缓存路径：levels=1:2 表示缓存目录层级为1/2，提升检索效率；keys_zone分配10m内存存储缓存元数据（约存储8000个缓存键）
    proxy_cache_path /var/nginx/cache 
                     levels=1:2 
                     keys_zone=web_cache:10m 
                     max_size=20g 
                     inactive=1h 
                     use_temp_path=off; # 关闭临时文件路径，避免磁盘IO竞争

    # 开启缓存共享：允许多个worker进程共享缓存
    proxy_cache_lock on;
    proxy_cache_lock_timeout 5s; # 缓存更新时，同一请求的并发锁超时时间

    server {
        listen 80;
        server_name www.example.com api.example.com;

        # 开启gzip压缩，提升缓存资源传输效率
        gzip on;
        gzip_types text/plain text/css application/javascript application/json;
        gzip_min_length 1k;

        # 静态资源缓存配置
        location ~* \.(png|jpg|jpeg|gif|css|js|ico)$ {
            proxy_cache web_cache;
            proxy_cache_key "$host$request_uri";
            proxy_cache_valid 7d; # 静态资源缓存7天
            proxy_cache_use_stale error timeout invalid_header updating http_500 http_502 http_503 http_504; # 后端异常时使用缓存降级
            proxy_headers_hash_max_size 512;
            proxy_headers_hash_bucket_size 128;
            proxy_pass http://backend_static; # 静态资源后端
            expires 7d; # 客户端缓存7天
        }

        # 动态接口缓存配置
        location /api/ {
            proxy_cache web_cache;
            proxy_cache_key "$host$request_uri$cookie_user"; # 包含用户标识，区分不同用户的缓存
            proxy_cache_valid 200 302 10m; # 成功响应缓存10分钟
            proxy_cache_valid 404 1m; # 404响应缓存1分钟，防穿透
            proxy_cache_valid 500 502 503 504 10s; # 错误响应缓存10秒，快速恢复
            proxy_no_cache $cookie_nocache $arg_nocache; # 携带nocache参数则不缓存
            proxy_cache_bypass $cookie_nocache $arg_nocache; # 携带nocache参数则绕过缓存
            proxy_cache_use_stale error timeout invalid_header updating http_500 http_502 http_503 http_504; # 缓存降级
            proxy_pass http://backend_api; # 后端API服务
        }

        # 缓存主动清理接口（需配合ngx_cache_purge模块）
        location ~ /purge(/.*) {
            proxy_cache_purge web_cache "$host$1";
            return 200 "Cache purged successfully: $host$1";
        }

        # 反向代理后端配置
        upstream backend_static {
            server 192.168.1.10:8080;
            server 192.168.1.11:8080 backup;
        }

        upstream backend_api {
            server 192.168.1.20:8080;
            server 192.168.1.21:8080 backup;
        }
    }
}