Distributed Cache Capabilities - Notifications

A notification system allows the cache to interact with external applications. This attribute can be useful on scenarios where certain activities, for example workflows, need to know the state of an item.

Capability	Description	Weight
Cache item notification	A cache item notification system  will allow clients to subscribe to any event associated with a specific cache  item. These notifications are usually handled by a disconnected proxy that  allows subscribers to hold an open channel with the notification service. The  cache item is usually decorated with a reference to the notification tables  and signals the entry when the item is modified, accessed or deleted.	2
Guideline	This feature can be useful in  scenarios where the cache is used as a pub/sub storage mechanism. But only  use this feature if the amount of clients is below 25 as there is a  performance penalty when using a notification system that can drag the update  times to unacceptable levels. If this model is required consider using cache  regions to minimize the overhead.
Capability	Description	Weight
Group Notification	Group notifications are an  advanced version of cache item notification. This model allows grouping  several items into a single notification model or to attach a notification to  the cache region or cache segment (similar to a table or database  notification in the database world).	2
Guideline	This feature can be useful in  scenarios where the cache is used as a pub/sub storage mechanism. But only  use this feature if the amount of clients is below 25 as there is a  performance penalty when using a notification system that can drag the update  times to unacceptable levels. If this model is required consider using cache  regions to minimize the overhead.
Capability	Description	Weight
Custom notifications	Some caches provide a custom  notification extensibility model where system developers can create custom  notifications. This capability is usually implemented with a transparent  proxy from the notification system to the external plug-in (usually  implemented through inversion of control).	3
Guideline	This capability will allow  developers to create their own notifications, this can involve external  systems. It is recommended to use async operations when notifying if the  cache uses the notifications model synchronically.