Apache config
=============

Ver orden en que usa los VirtualHosts  
``` apache2ctl -S ```

Forzar redirects con el servername del virtualhost  
``` UseCanonicalName On ```

Ver variables del servidor  
```
<?php
phpinfo(INFO_VARIABLES);
?>
```

Proxy Pass
----------

URL con caracteres raros  
``` 'nocanon ```
- Pasa la URL sin canonicalizar tal como la recibe. 
- Sirve para servicios REST que necesitan pasar parámetros con acentos
``` ProxyPass /webservice balancer://api/webservice nocanon ```

Excluir un path del ProxyPass  
``` ProxyPass /ciudades/aulavirtual ! ```
``` ProxyPass /ciudades/ balancer://ciudades_hcluster/ciudades/ ```
``` ProxyPassReverse /ciudades/ balancer://ciudades_hcluster/ciudades/ ```

Pasar / en la url  
``` AllowEncodedSlashes```

Sobreescribir página de error  
``` ProxyPass /error-documents ! ```
``` ErrorDocument 503 /error-documents/503.html ```
``` Alias /error-documents /home/stefan/repos/empfehlungsbund/public ```

Cache
-----

- Para que funcione además de habilitar el módulo hay que decomentar ```CacheEnable disk /``` en la configuración del módulo
- El directorio de cache se puede configurar por VirtualHost (pero hay que agregarlo al htcacheclean)
- Las urls que se cachean se pueden configurar por VirtualHost
- Siempre que trae algo del cache aparece el header "Age: X"

Directivas que afectan al cache
``` CacheQuickHandler Off ``` (2.4) para que revise si la url está permitida antes de buscar en el caché
``` UseCanonicalName On ``` Todos los accesos al virtualhost usan la misma url cacheada

Apache 2.2
----------

```
# Log
SetEnv CACHE_MISS 1
Header append CacheMISS %`CACHE_MISS`e
LogFormat "%h %l %u %t \"%r\" %>s %b MISS:%`CACHE_MISS`e %`Age`o" cache
```

Apache 2.4
----------

Evitar que sirva el cache antes de procesar las directivas de url (para que no traiga del cache cosas prohibidas por location)  
Sólo funciona en la configuración general del módulo  
```CacheQuickHandler off```

```
# Enable the X-Cache header
CacheHeader on

# Enable the X-Cache-Detail header
CacheDetailHeader on

# Log
LogFormat "%h %l %u %t \"%r\" %>s %O %`cache-status`e %`Age`o" cache
```


What Can be Cached?
-------------------

The full definition of which responses can be cached by an HTTP cache is defined in RFC2616 Section 13.4 Response Cacheability, and can be summed up as follows:

  - Caching must be enabled for this URL. See the CacheEnable and CacheDisable directives.
  - The response must have a HTTP status code of 200, 203, 300, 301 or 410.
  - The request must be a HTTP GET request.
  -  If the response contains an "Authorization:" header, it must also contain an "s-maxage", "must-revalidate" or "public" option in the "Cache-Control:" header, or it won't be cached.
  - If the URL included a query string (e.g. from a HTML form GET method) it will not be cached unless the response specifies an explicit expiration by including an "Expires:" header or the max-age or s-maxage directive of the "Cache-Control:" header, as per RFC2616 sections 13.9 and 13.2.1.
  - If the response has a status of 200 (OK), the response must also include at least one of the "Etag", "Last-Modified" or the "Expires" headers, or the max-age or s-maxage directive of the "Cache-Control:" header, unless the CacheIgnoreNoLastMod directive has been used to require otherwise.
  - If the response includes the "private" option in a "Cache-Control:" header, it will not be stored unless the CacheStorePrivate has been used to require otherwise.
  - Likewise, if the response includes the "no-store" option in a "Cache-Control:" header, it will not be stored unless the CacheStoreNoStore has been used.
  - A response will not be stored if it includes a "Vary:" header containing the match-all "*".

** Problemas con proxypass en apps que no ven la IP del cliente **

Si se le cierra la sesión con el mensaje de que la IP del cliente cambió y hay dos apaches de frontend que hacen reverse proxy.

** mod_rpaf **  

It changes the remote address of the client visible to other Apache modules when two conditions are satisfied. First condition is that the remote client is actually a proxy that is defined in httpd.conf. Secondly if there is an incoming X-Forwarded-For header and the proxy is in it's list of known proxies it takes the last IP from the incoming X-Forwarded-For header and changes the remote address of the client in the request structure.
In this case rpaf translates the remote address 192.168.20.50 to real client address sent in X-Forwarded-For header.

```
RPAFsethostname On
RPAFproxy_ips 192.168.13.31 192.168.13.32
```