ObserverCache
Related Doc:
package iface
The maximum size of the active cache. If get would cause the active cache to exceed this size, a MaximumObservationsReached exception is returned instead.
The maximum size of the inactive cache. LRU eviction is used to maintain this constraint.
The function to use to create new Observers if they are not in either cache.
A cache for Observer[T]. ObserverCache contains two levels of caching: active and inactive.
The active cache is for Observers that have current outstanding requests against them. Therefore, any Observer in the active cache must not be closed as this would cause the outstanding requests to hang.
The inactive cache is for Observers without outstanding requests against them. These Observers are kept open while in the inactive cache in case they receive a request and need to be moved to the active cache. The inactive cache has LRU eviction and Observers are closed upon eviction. Since Observers in the inactive cache have no outstanding requests against them, this is safe to do.
When get is called, the Observer for that key is moved to the active cache if it exists or created and placed in the active cache if it does not exist. When the value of an Observer in the active cache changes, the Observer is moved to the inactive cache. If the inactive cache is full at that time, an older inactive Observer will be evicted.