带有错误502的Nginx反向代理仅在按端口动态映射

Question

我尝试将后端NodeJS Docker容器从端口映射到子域。为此，我尝试配置：

map $sub $prt {
        include /var/www/ports.map;
}

server {

        listen 443 ssl http2;
        listen [::]:443 ssl http2;

        ssl_certificate         /var/...;
        ssl_certificate_key     /var/...;
        ssl_trusted_certificate /var/...;

        server_name ~^(?P<sub>.+?)-api\.cnpgc\.embrapa\.br$;

        location / {
                add_header x-sub "$sub";
                add_header x-prt "$prt";

                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection 'upgrade';
                proxy_set_header Host $host;
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header X-Forwarded-Proto $scheme;
                proxy_cache_bypass $http_upgrade;
                proxy_ssl_session_reuse off;
                proxy_pass http://localhost:$prt;
        }

}

但是，当尝试访问例如“ cria-certo-api.cnpgc.embrapa.br”时，出现错误“ 502 Bad Gateway”。如果我将最后一行从

proxy_pass http://localhost:$prt;

到

proxy_pass http://localhost:9080;

代理正常工作！因此，出现此错误是由于URL中存在变量“ $ prt”引起的。这没有道理。

我用行调试地图：

add_header x-sub "$sub";
add_header x-prt "$prt";

它也起作用。有帮助吗？