ecfad6ad_Administration_Guide__Description
[Property Name] CallbackThreads [Default Value] 5 [Description] 
When sweeping the pool for expired instances a thread pool is used to process calling @PreDestroy on expired instances as well as creating new instances as might be required to fill the pool to the minimum after a Flush or MaxAge expiration. The CallbackThreads setting dictates the size of the thread pool and is shared by all beans deployed in the container.
Administration Guide
Description