mod_proxy_balancer

debian

/etc/apache2/mods-available/proxy.conf を編集。
mongrel が 192.168.0.100 の 3000〜3002 で動いてると仮定して。

  <Proxy *>
    AddDefaultCharset off
    Order deny,allow
    Deny from all
    #Allow from .example.com
    Allow from all

    # Define the character set for proxied FTP directory listings
    ProxyFtpDirCharset UTF-8
  </Proxy>

  ...

  ProxyPass / balancer://mongrel/ timeout=2
  ProxyPassReverse / balancer://mongrel/
  <Proxy balancer://mongrel>
    AddOutputFilterByType DEFLATE test/html text/css application/x-javascript
    BalancerMember http://192.168.0.100:3000 loadfactor=10 keepalive=On
    BalancerMember http://192.168.0.100:3001 loadfactor=10 keepalive=On
    BalancerMember http://192.168.0.100:3002 loadfactor=10 keepalive=On
  </Proxy>

mongrel のとこは何でも良い。

$ sudo a2enmod proxy
$ sudo a2enmod proxy_http
$ sudo a2enmod proxy_balancer

proxy_http を enable にし忘れててはまった。