如何在Nginx中实现文件存在则本地返回，否则反向代理？

需求概述 #

• 搭建BLOB服务，负责图片、视频、音频等静态资源分发，请求示例：https://blob.example.com/blogPost/background.webp
• Nginx优先检查本地硬盘中是否存在请求的文件，存在则直接返回给客户端
• 若文件不存在，Nginx将请求反向代理至上游应用，由上游应用从云存储异步下载文件并保存到本地目录，供后续请求直接复用

现有Nginx配置 #

server
{
    listen 80;
    server_name example.com;
    return 301 https://$server_name$request_uri;
}

server
{
    listen 443 http2 ssl;
    server_name example.com;
    client_max_body_size 0;

    ssl_certificate /Project/SiteQwik/Certificate.pem;
    ssl_certificate_key /Project/SiteQwik/Key.pem;

    error_page 502 /502.html;

    location /502
    {
        root /Base/Infra/Nginx;
        internal;
    }

    location /
    {
        proxy_pass http://localhost:56710;
        proxy_set_header X-Forwarded-Host $host;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_set_header Host $host;
    }
    
    location ~ ^/(fa|en|ar|ru|tr)(/|$) {
        rewrite ^/(fa|en|ar|ru|tr)/(.*)$ /$2?locale=$1 break;
        rewrite ^/(fa|en|ar|ru|tr)$ /?locale=$1 break;
        proxy_pass http://localhost:56710;
        proxy_set_header X-Forwarded-Host $host;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_set_header Host $host;
    }
}

改造后的完整配置 #

# 保留原example.com的配置不变
server
{
    listen 80;
    server_name example.com;
    return 301 https://$server_name$request_uri;
}

server
{
    listen 443 http2 ssl;
    server_name example.com;
    client_max_body_size 0;

    ssl_certificate /Project/SiteQwik/Certificate.pem;
    ssl_certificate_key /Project/SiteQwik/Key.pem;

    error_page 502 /502.html;

    location /502
    {
        root /Base/Infra/Nginx;
        internal;
    }

    location /
    {
        proxy_pass http://localhost:56710;
        proxy_set_header X-Forwarded-Host $host;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_set_header Host $host;
    }
    
    location ~ ^/(fa|en|ar|ru|tr)(/|$) {
        rewrite ^/(fa|en|ar|ru|tr)/(.*)$ /$2?locale=$1 break;
        rewrite ^/(fa|en|ar|ru|tr)$ /?locale=$1 break;
        proxy_pass http://localhost:56710;
        proxy_set_header X-Forwarded-Host $host;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_set_header Host $host;
    }
}

# 新增BLOB服务专属Server块
server
{
    listen 80;
    server_name blob.example.com;
    return 301 https://$server_name$request_uri;
}

server
{
    listen 443 http2 ssl;
    server_name blob.example.com;
    client_max_body_size 0;

    # 复用原有通配符证书，若为单域名证书需替换为对应证书路径
    ssl_certificate /Project/SiteQwik/Certificate.pem;
    ssl_certificate_key /Project/SiteQwik/Key.pem;

    # 本地BLOB文件存储根目录，需根据实际环境修改
    root /var/blob-storage;

    # 核心逻辑：优先返回本地文件，不存在则转发至上游
    location / {
        try_files $uri @fetch_from_upstream;
        # 可选：添加静态资源缓存策略，优化客户端体验
        expires 30d;
        add_header Cache-Control "public, immutable";
    }

    # 上游应用转发配置，需替换为实际上游服务地址
    location @fetch_from_upstream {
        proxy_pass http://localhost:56710;
        proxy_set_header X-Forwarded-Host $host;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        # 传递原始请求URI，供上游应用定位云存储文件
        proxy_set_header X-Original-URI $request_uri;
    }
}

关键配置说明 #

• 独立Server隔离：新增blob.example.com专属Server块，与原有业务请求完全隔离，避免互相干扰
• 本地文件检测逻辑：try_files $uri @fetch_from_upstream是核心指令，Nginx会先在root目录下匹配请求URI对应的文件，找到则直接返回；未找到则触发上游转发
• 上游协作要求：上游应用需要通过X-Original-URI头或原始请求URI定位云存储文件，下载后必须保存到/var/blob-storage目录的对应路径下（比如请求/blogPost/background.webp需保存为/var/blob-storage/blogPost/background.webp）
• 缓存优化：添加的expires和Cache-Control头可让客户端长期缓存静态资源，减少重复请求次数

内容的提问来源于stack exchange，提问作者Ali Radan