Nginx X-Accell-Redirect 给出 502 错误网关

Question

我想允许用户从远程存储下载文件，但我想先通过我的 rails 应用程序验证请求。我想在 rails 验证请求后将远程文件的代理移交给 nginx，以释放 ruby​​/rails 线程。

我有一个名为 proxy_download.conf 的 nginx conf 文件：

   # Proxy download 
   location ~* ^/internal_redirect/(.*?)/(.*) {
     # Do not allow people to mess with this location directly
     # Only internal redirects are allowed
     internal;

     # Location-specific logging
     access_log logs/internal_redirect.access.log combined;
     error_log logs/internal_redirect.error.log warn;

     # Extract download url from the request
     set $download_uri $2;
     set $download_host $1;

     # Compose download url
     set $download_url http://$download_host/$download_uri;

     # Set download request headers
     proxy_set_header Host $download_host;
     proxy_set_header Authorization '';

     # The next two lines could be used if your storage 
     # backend does not support Content-Disposition 
     # headers used to specify file name browsers use 
     # when save content to the disk
     proxy_hide_header Content-Disposition;
     add_header Content-Disposition 'attachment; filename="$args"';

     # Do not touch local disks when proxying 
     # content to clients
     proxy_max_temp_file_size 0;

     # Download the file and send it to client
     proxy_pass $download_url;
   }

我将其导入到主 nginx 配置中，如下所示：

include $ROOT/TO/APP/nginx.conf.d/proxy_download.conf;

通过此设置，应用程序可以顺利部署并正常运行。

这些是启动下载请求的控制器方法：

  def x_accel_url(url, file_name = nil)
    uri = "/internal_redirect/#{url.gsub('http://', '').gsub('https://', '')}"
    uri << "?#{file_name}" if file_name
    return uri
  end

def download
    if auth_is_ok # do some auth logic here
        headers['X-Accel-Redirect'] = x_accel_url('http://domain.com/file.ext')
        render :nothing => true
    end
end

当通过浏览器访问此控制器方法时，我得到了著名的 nginx 错误：

502 Bad Gateway

我的设置有什么问题？谢谢！