server_block with proxy reverse nginx

nginx_server_block

#BLOCO-1
upstream myzap-v2 {
    server 127.0.0.1:3333;
    keepalive 8;
}
server {
    server_name SERVER_API;

    location / {
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header Host $http_host;
      proxy_set_header X-NginX-Proxy true;
      proxy_pass http://myzap-v2/;
      proxy_redirect off;
    }

    listen 80;

}