Nginx 缓存与压缩优化：proxy_cache 与 gzip 实战

location ~* \.(css|js|png|jpg|jpeg|gif|webp|svg|woff2)$ {
    expires 30d;                          # 输出 Cache-Control: max-age=2592000
    add_header Cache-Control "public, max-age=2592000, immutable";
}

# 带 hash 指纹的静态资源可以放心长缓存
location /static/ {
    expires 1y;
    add_header Cache-Control "public, immutable";
}

proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=mycache:100m
                 inactive=60m max_size=2g;

location / {
    proxy_pass http://backend;
    proxy_cache mycache;
    proxy_cache_key "$scheme$request_method$host$request_uri";
    proxy_cache_valid 200 302 10m;
    proxy_cache_valid 404 1m;
}

location /api/ {
    proxy_pass http://backend;
    proxy_cache mycache;
    proxy_cache_valid 200 302 60m;
    proxy_cache_valid 404 500 502 503 1m;
    proxy_cache_valid any 1m;
    proxy_ignore_headers Cache-Control Set-Cookie;   # 忽略上游缓存头
}

# 带 ?nocache=1 的请求绕过缓存直接回源
location /api/ {
    proxy_pass http://backend;
    proxy_cache mycache;
    proxy_cache_bypass $arg_nocache;
    proxy_no_cache $arg_nocache;
}

# 指定请求头也能触发绕过（如内部刷新接口）
proxy_cache_bypass $http_x_purge;

proxy_cache_lock on;                 # 同键并发请求只放一个回源，其余等待
proxy_cache_lock_timeout 5s;         # 等待超时后也放行
proxy_cache_use_stale updating;      # 回源期间用旧缓存兜底

add_header X-Cache-Status $upstream_cache_status;

# 从 access log 统计缓存命中率
awk '{print $NF}' /var/log/nginx/access.log \
  | sort | uniq -c | sort -rn
# 期望 HIT 占比在 80% 以上

gzip on;
gzip_min_length 1024;                       # 小于 1KB 不压缩
gzip_comp_level 5;                          # 1~9，默认 1，建议 4~6
gzip_types text/plain text/css application/json
           application/javascript application/xml
           image/svg+xml;                    # 只压缩文本类
gzip_vary on;                                # 输出 Vary: Accept-Encoding
gzip_disable "msie6";

brotli on;
brotli_min_length 1024;
brotli_comp_level 6;
brotli_types text/plain text/css application/json application/javascript;

gzip_static on;        # 命中同名 .gz 文件直接发送
brotli_static on;      # 命中同名 .br 文件直接发送

# 构建期预压缩
gzip -k -9 dist/app.js
brotli -k -q 11 dist/app.js

proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=api_cache:50m
                 inactive=60m max_size=1g;

server {
    location / {
        proxy_pass http://backend;
        proxy_cache api_cache;
        proxy_cache_lock on;
        proxy_cache_use_stale updating error timeout;
        add_header X-Cache-Status $upstream_cache_status;

        gzip on;
        gzip_min_length 1024;
        gzip_comp_level 5;
        gzip_types text/plain text/css application/json application/javascript;
        gzip_vary on;
    }
}

请求 → 网关层（命中缓存？）→ 命中则返回压缩缓存 / 未命中回源
      → 上游响应 → 按需 gzip 压缩 → 写入缓存 → 返回客户端

# 按 key 主动清理缓存（需 ngx_cache_purge 模块）
curl -X PURGE http://example.com/api/user/1
# 或直接删除磁盘缓存文件
find /var/cache/nginx -name "*" -type f -mtime +1 -delete