Blue Coat Systems Time Clock Proxy SG Manual De Usuario

ProxySG Content Policy Language Guide

38

•

The optional 

is a list of properties set if any of the rules in the layer match. 

These act as defaults, and can be overridden by property settings in specific rules in the layer. For 
more information on using properties, see Chapter 4: "Property Reference". See also the following 
Layer Guards section.

<Cache> Layers

<Cache>

 layers hold policy that is executed by both cache and proxy transactions. Since cache 

transactions have no concept of a client, all 

<Cache>

 layer policy is clientless, so you cannot test client 

identity using 

client.address=, user=, group=

, and the like.

Certain types of policy must be applied consistently to both proxy and cache transactions to preserve 
cache consistency. Such policy must not be conditional on client identity or time of day, and belongs in 
a 

<Cache>

 layer. Examples include the following:

•

Response virus scanning.

•

Cache control policy (other than 

bypass_cache

).

•

Modifications to request headers, if the modification affects the content returned by the web 
server, and the content is cached.

•

Rewrites of the request URL that modify the server URL but not the cache URL. (Place rewrites of 
the request URL that change the cache and server URL to the same value in a 

<Proxy>

 layer.)

Only the following properties are safe to make conditional on time or client identity in a 

<Cache>

 

layer:

•

Pipelining

•

Tracing, logging

•

Freshness checks

•

Redirection

•

Content transforms

The syntax is:

<Cache [label]> [cache_condition][cache_properties] ...

where:

•

The 

<Cache>

 layer defines the transactions evaluated against this policy, and restricts the triggers 

and properties allowed in the rules used in the layer.

•

The optional 

 separated from the layer type by space, is a CPL User-defined Identifier. 

•

The optional 

 is a list of triggers, all of which must evaluate to true before the 

layer content is evaluated. For more information on using conditions, see Chapter 3: "Condition 
Reference". See also the following Layer Guards section.

•

The optional 

is a list of properties set if any of the rules in the layer match. 

These act as defaults, and can be overridden by property settings in specific rules in the layer. For 
more information on using properties, see Chapter 4: "Property Reference". See also the following 
Layer Guards section.