Jogue! Framework: Apache mod_proxy ocasionalmente entrega erro de proxy

Question

O backend é um jogo! Aplicativo de estrutura.

Proxy Error

The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request GET /entries/topic~showcase

Reason: Error reading from remote server

Apache/2.2.22

Aqui está a configuração do site:

<VirtualHost *:80>
  ProxyPreserveHost On
  ServerName www.xxx.com
  ServerAlias xxx.com
  ProxyPass  /excluded !
  ProxyPass /investor http://127.0.0.1:81/investor
  ProxyPass /phppgadmin http://127.0.0.1:81//phppgadmin
  ProxyPass / http://127.0.0.1:9000/ keepalive=On
  ProxyPassReverse / http://127.0.0.1:9000/
</VirtualHost>

Depois de adicionar keepalive = On , pude notar uma melhoria. Mas o erro de proxy ainda ocorre!