nginx and node deployment config

nginx.conf

upstream myapp_new {
  server unix:/tmp/myapp-new.sock;
}

upstream myapp_old {
  server unix:/tmp/myapp-old.sock;
}

server {
  location / {
    error_page 502 503 504 = @failover;
    proxy_next_upstream error timeout http_500 http_502 http_503 http_504 http_404;
    proxy_intercept_errors on;    
    proxy_pass http://myapp_new;
    break;
  }

  location @failover {
    proxy_next_upstream error timeout http_500 http_502 http_503 http_504 http_404;
    proxy_intercept_errors on;    
    proxy_pass http://myapp_old;
    break;
  }
}