Netra j 3.0 Administrator's Guide

URL Policy

There are two URL Policy properties.

Table 10-7 URL Policy Properties


Property	Description
Do not Query Neighbors for URLS Containing	For URLs containing strings you add to this list, the Netra j proxy cache server looks in its own cache and does not query parent caches.
TTL Selection Based on URL	The Netra j proxy cache server enables you to set the Time To Live for URLs containing strings that you specify (see below).

Setting the TTL for URLs

You can specify a URL's Time To Live in either of two ways: as an absolute value or as a percentage of an object's age. Entries have the following form:

reg_expression absolute_TTL percentage maximum_TTL

where:

reg_expression is a regular expression that is matched against a URL. See "Rules for Pattern Matching for TTL Selection Property" for rules for the regular expression.

absolute_TTL is the TTL (in minutes) used by the Netra j proxy cache server if the percentage method is not used.

percentage is the percentage of the duration between an object's last-modified timestamp and the current time.

maximum_TTL is the upper limit (in minutes) on the TTL.

The proxy cache uses the percentage method of determining the TTL if a matched object has a last-modified timestamp. If an object does not have such a timestamp, the absolute TTL is used instead. You can specify a negative value for absolute_TTL thereby forcing the percentage method to be used. If a matched object then does not have the required timestamp, the TTL is set from a value set under Cache Policy (see Step 2 in "To View or Modify Cache Policy Properties").

If neither the absolute TTL nor percentage methods result in a TTL for a matched object, the TTL is determined from the values set in the Cache Policy properties.

The Netra j proxy cache server checks all patterns in the list and uses the last match.

The following is an example of a TTL-selection entry:

^http:// 1440 20 43200

The preceding example matches URLs that start with http://. If a URL contains a last-modified timestamp, the TTL for that URL is set to 20% of the difference between the timestamp and the current time. If the URL does not have such a timestamp, the TTL is set to 1440 minutes. In any event, the URL will not stay in the cache longer than 43200 minutes.