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Show / Hide Table of Contents
  • Programmer's Guide
  • Client Side API Programming
    • Setting Up Development Environment
    • Basic Cache Operations
      • Initialize Cache
      • Add Data to Cache
      • Update Data in Cache
      • Fetch Data From Cache
      • Remove Data From Cache
      • Dispose Cache
    • Bulk Operations
      • Adding Collection to Cache
      • Updating Collection in Cache
      • Retrieving Collection from Cache
      • Removing Collection from Cache
      • Deleting Collection from Cache
    • Asynchronous Operations
      • Using Asynchronous Operations
      • Using Asynchronous Operations with Callback Methods
    • Groups and Subgroups
      • Adding/Updating Data Group in Cache
      • Retrieving Data Group from Cache
      • Removing Data Group from Cache
    • Tagging Data in NCache
      • Creating Tags
      • Adding Items with Tags
      • Retrieving Previously Tagged Data
      • Removing Tagged Items from Cache
    • Named Tags
    • Data Expiration Strategies
      • Using Absolute Expiration
      • Using Sliding Expiration
    • Cache Dependencies
      • Key Dependency
      • File Dependency
      • Notification based Dependencies
        • Database Dependency using SQL Server
        • Database Dependency using Oracle
      • Polling Based Dependency
      • Custom Data Source Dependency
      • Multiple Cache Sync Dependency
      • Aggregate Dependency
      • Add Dependency to Existing Item
      • Using CLR Procedures to Call NCache
    • Locking Data in NCache
      • Locking Items in Cache (Pessimistic Locking)
      • Locking Items with Cache Item Versioning (Optimistic Locking)
    • SQL Reference for NCache
      • SQL Syntax
      • Querying Samples for Operators
      • Querying Data in NCache
      • NCache Language Integrated Query (LINQ)
        • Using LINQ in NCache
        • Configuring LINQPad for NCache
        • Querying NCache Data in LINQPad
    • Event Notifications
      • Cache Level Event Notifications
      • Item Level Event Notifications
      • Custom Event Notifications
    • Publish/Subscribe (Pub/Sub) in NCache
      • Pub/Sub Topics
      • Managing Topics
      • Pub/Sub Messages
        • Message Behavior and Properties
        • Creating a Message
      • Publish Messages to Topic
      • Subscribe for Topic Messages
      • Monitoring Pub/Sub Topics
    • Continuous Query
    • Using Streams in NCache
      • Opening with Stream Modes
      • Adding and Updating Data with Streams
      • Retrieving Data from Streams
      • Closing a Stream
    • Security and Encryption
      • NCache Security
      • NCache Data Encryption
    • Data Compression
    • NCache Management API
  • Server Side API Programming
    • Cache Startup Loader
      • Components of Cache Startup Loader
      • Sample Implementation of ICacheLoader on Single Node
      • Sample Implementation of ICacheLoader with Distribution Hints
    • Data Source Providers (Backing Source)
      • Read-Through Caching
        • Configure Read-Through Provider
        • Using Read-Through with Cache Operations
      • Write-Through Caching
        • Configuring Write-Through Provider
        • Using Write-Through with Basic Operations
        • Using Write-Behind with Basic Operations
        • Using Write-Behind with Bulk Operations
        • Using Write-Behind with Async Operations
        • Monitor Write-Through Counters
    • Custom Dependency
      • Sample Implementation of Custom Dependency
      • Sample Usage of Custom Dependency
    • WAN Replication through Bridge
      • Bridge Configurations
      • Implementing Bridge Conflict Resolver
    • Entry Processor
      • Sample Implementation of IEntryProcessor Interface
      • Sample Usage of EntryProcessor
    • MapReduce
      • Sample Implementation of MapReduce Interfaces
      • Sample Usage of MapReduce
    • Aggregator
      • Sample Implementation of IValueExtractor Interface
      • Sample Implementation of IAggregator Interface
      • Sample Usage of Aggregator
    • Dynamic Compact Serialization
  • Client Side ASP.NET Features
    • ASP.NET
      • ASP.NET Session State Provider for NCache
      • Multi-Region ASP.NET Session State Provider for NCache
    • ASP.NET Core
      • Session Storage in ASP.NET Core
        • Configure NCache ASP.NET Core Session Provider
        • Configure ASP.NET Core Sessions with NCache IDistributedCache Provider
      • Multi-Region ASP.NET Core Session Provider for NCache
      • Object Caching in ASP.NET Core
    • ASP.NET SignalR
      • Using NCache Extension for SignalR
    • View State Caching
      • Configuring and Using Content Optimization
      • Group View State with Sessions
      • Limit View State Caching
      • Perform Page Level Grouping for View State
    • ASP.NET Output Cache
      • Configure ASP.NET Output Caching
      • Using ASP.NET Output Cache with Custom Hooks
  • Client Side Third Party Integrations
    • Migrating AppFabric to NCache
      • AppFabric API vs. NCache API
    • NHibernate
      • NCache as NHibernate Second Level Cache
      • Using NHibernate Query Caching
      • Configuring Database Synchronization with NHibernate
    • Entity Framework Caching Integration
      • NCache as Entity Framework Second Level Cache
      • Entity Framework Caching Config File
    • Entity Framework Core Caching
      • Installing NCache Entity Framework Core Provider
      • Configuring NCache Entity Framework Core Provider
      • Using NCache Entity Framework Core Provider
        • Caching Options for EF Core Provider
        • LINQ APIs for EF Core Provider
        • Cache Only APIs for EF Core Provider
        • Query Deferred APIs for EF Core Provider
      • Logging in NCache Entity Framework Core Provider
    • Memcached
      • NCache Memcached Gateway Approach
      • Memcached Client Plugin for .NET
    • Debug NCache Providers in Visual Studio
    • NCache for Visual Studio Extension

Event Notifications

Many applications today need to share data asynchronously with each other at runtime, and relational databases do not provide an efficient event notification mechanism. Hence, their performance and scalability is a major concern.

NCache features event driven fetching of data every time data in the cache is modified. This allows client applications to receive data without any explicit data fetch request to the cache server. Events work on the push mechanism: whenever some activity of interest takes place in cache, it publishes events to its subscribed clients. This allows runtime data sharing of single cache shared by separate applications or separate modules of same application.

Events enable NCache to notify the client application if any change of interest occurs. Events in NCache follow the publisher-subscriber model where cache is the publisher and client application is the subscriber.

Events have the following properties:

  • The publisher determines when an event is raised; the subscribers determine what action is taken in response to the event.

  • An event can have multiple subscribers. A subscriber can handle multiple events from multiple publishers.

  • Events are typically used to signal common cache operations like Add, Insert, Remove, Delete and Cache Cleared.

Events and Event Types

  • Add Notification
    Add notification is triggered when a new item is added to the cache. All applications which have registered this event will receive a notification when data is added to the cache.

  • Update Notification
    Update notification is triggered when an existing item is updated in the cache. All applications which have registered this event will receive a notification when data is updated in the cache.

  • Remove Notification
    Remove notification is triggered when an item is removed from the cache. All applications which have registered this event will receive a notification when data is removed from the cache.

  • Cache Clear Notification
    Cache Clear notification is triggered when cache is cleared. All applications which have registered this event will receive a notification when the cache is cleared.

Event Levels

NCache provides the following level of events:

  • Cache Level Events
    NCache can notify clients on addition, insertion, and removal of any item in the cache or if the cache is cleared, if the client has registered interest in receiving such events.

  • Item Level Events
    NCache can notify clients on a specific item update and remove if the client has registered interest in it.

  • Continuous Query Events
    NCache can monitor a dataset in the cache based on SQL-like criteria and then notify clients for addition, insertion, and removal of items from this data set to clients who have registered interest in it.

  • Application Initiated Custom Events
    Applications can fire custom events into NCache so other applications who have registered interest in them can be notified.

In This Section

Cache Level Data Event Notifications
Explains how to use notification mechanism for events occurring at cache level.

Item Level Data Event Notifications
Explains how to use notification mechanism for events occurring at item level.

Custom Event Notifications
Explains how to use custom events and notification mechanism provided by NCache.

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