Used by {@link org.apache.tapestry5.internal.services.PagePoolImpl} to maintain a cache of available and in-use pageinstances.
This code is designed to handle high volume sites and deal with request fluctuations.
Page instances, once created, are tracked with
soft references.
A
soft limit on the number of page instances is enforced. Requesting a page instance when the soft limit has been reached (or exceeded) will result in a delay until a page instance (released from another thread) is available. The delay time is configurable.
A
hard limit on the number of page instances is enforced. This number may not be exceeded. Requesting a page instance when at the hard limit will result in a runtime exception.