Nginx 反向代理 - 绕过带有 404 代码的服务器

Question

我想知道是否有办法设置 NGINX 反向代理来“绕过”以 404（或其他错误代码）响应的列表中的服务器。

我有一个集群图像板，我正在通过 6 台专用服务器批量导入图像，这些服务器不属于集群，因为它们不使用共享存储。当图像导入实时系统时，集群中的其他服务器显然会响应 404，因为它们无法访问位于导入服务器上的文件。

有没有办法可以将它们添加到 NGINX 上的列表中，并且它会忽略以 404 响应的服务器并使用正确响应的服务器？

我的 NGINX 反向代理配置：

upstream sequenzia-press {
#   server node-end1:80;
    server node1:80;
    server node2:80;
    server node3:80;
    server node4:80;
  }
upstream sequenzia-cpu {
    server node1:80;
    server node2:80;
    server node3:80;
    server node4:80;
  }
server {
        listen 80;
        root /var/www/html;
        server_name sequenzia.acr.moe;
        rewrite        ^ https://$server_name$request_uri? permanent;
}

server {
        listen 443 ssl;
        root /var/www/seq;
        server_name sequenzia.acr.moe;
        ssl_certificate      /etc/apache2/keyset/fullchain.pem;
        ssl_certificate_key  /etc/apache2/keyset/privkey.pem;
        ssl_protocols        TLSv1 TLSv1.1 TLSv1.2;
        ssl_ciphers          RC4:HIGH:!aNULL:!MD5;
        ssl_prefer_server_ciphers on;
        keepalive_timeout    70;
        ssl_session_cache    shared:SSL:10m;
        ssl_session_timeout  10m;
        client_max_body_size 500M;

        location / {
                add_header TangledFramework-Proxy-Datacenter Nagatenjouki/Core-MD;
                add_header TangledFramework-Proxy-Network Nagatenjouki/Production;
                add_header TangledFramework-Proxy-Transit Nagatenjouki/Shirai;
                add_header TangledFramework-Proxy-Service Sequenzia_Delivery;
                proxy_pass  http://sequenzia-cpu$request_uri;
        }
        location /post/import {
                add_header TangledFramework-Proxy-Datacenter Orion/Endymion-ATL-1;
                add_header TangledFramework-Proxy-Network Orion-Edge-CDN/Primary;
                add_header TangledFramework-Proxy-Transit Orion-Edge-A/Shirai-1;
                add_header TangledFramework-Proxy-Service Sequenzia_Delivery;
                proxy_pass  http://<Import RPC>$request_uri;
        }
        location /data {
                add_header TangledFramework-Proxy-Datacenter Orion/Endymion-ATL-1;
                add_header TangledFramework-Proxy-Network Orion-Edge-CDN/Primary;
                add_header TangledFramework-Proxy-Transit Orion-Edge-A/Shirai-1;
                add_header TangledFramework-Proxy-Service Sequenzia_Delivery;
                proxy_pass  http://sequenzia-press$request_uri;
        }
        location /se4trp {
                root /var/www/err;
                expires max;
        }
}