Apache Reference: mod_proxy, CacheGcInterval
Interval Between Proxy Cache Garbage Collections
Syntax: CacheGcInterval A
Example: CacheGcInterval 48
Since: Apache 1.1
This directive instructs the proxy server to check the document cache at the interval specified in the hours argument, and to delete files if the space usage exceeds that set by CacheSize. Note that the hours argument can contain float value.For example, you can use ``
1.5'' to check the cache every 90 minutes. Keep in mind that, by default, no garbage collection is performed and the cache will grow indefinitely. The larger the hours argument, the more extra space beyond the configured CacheSize that will be needed for the cache between garbage collections.