expression examines data in request-time transaction, and a response-time
expression examines data in a response-time transaction. In a policy for
caching, if an expression matches data in a request or response, the Citrix
NetScaler appliance takes the action associated with the policy. In a
selector, request-time expressions are used to find matching responses that are
stored in a content group.
policies and selectors for the integrated cache, you need to know, at minimum,
the host names, paths, and IP addresses that appear in HTTP request and
response URLs. And you probably need to know the format of entire HTTP requests
and responses. Programs such as Live HTTP Headers (http://livehttpheaders.mozdev.org/) or HTTPFox
can help you investigate the structure of the HTTP data that your organization
Following is an
example of an HTTP GET request for a stock quote program:
GET /quote.dll?page=dynamic&mode=data&mode=stock&symbol=CTXS&page=multi&selected=CTXS&random=0.00792039478975548 HTTP/1.1
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0
When configuring an
expression, note the following limitations:
Table 1. Restrictions on
Request-Time and Response-Time Expressions
configure request-time expressions in a policy with a CACHE or NOCACHE action.
Use MAY_CACHE or MAY_NOCACHE instead.
response-time expressions in caching policies only.
- Selectors can use only
- Do not configure
response-time expressions in a policy with an INVAL action.
configure response-time expressions in a policy with a CACHE action and a
parameterized content group. Use the MAY_CACHE action.