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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

Implementing Bridge Conflict Resolver

In bridge topology, there can be more than one active site cache and cache operations can be simultaneous. It is possible that the client connected with one active site cache adds some keys and the same key operation is performed by the other active node. In such a situation the bridge conflict resolver comes into play. It resolves the conflicts and decides which key to apply on the cache depending upon the defined rules.

If the user hasn't configured any conflict resolver rules, then NCache uses the default resolver rule. In the default rule, a timespan is added with each operation performed on the cache and it keeps the latest operation. A check is performed on the version of the bridge item. If it has a newer time stamp or if the version is the latest or the same it replaces that with the new entry and in case of old, it keeps the old entry.

IBridgeConflictResolver Interface

To utilize the interface, include the following namespace in your application: Alachisoft.NCache.Runtime.Bridge.

Method Description
Init This method performs tasks like allocating resources, acquiring connections etc. When cache is initialized and Conflict Resolvers are enabled, Init() method is called to notify the client that cache is initializing and you can initialize your conflict resolver via Init(). The parameters passed as an argument contains all the parameters (if any) that were specified using NCache Manager cache/cluster views. These parameters can be utilized in many ways.
Dispose This method performs tasks like releasing the resources etc. When the cache is stopped or the task is completed, it calls the Dispose() method to notify the client that resources related to the task can be freed.
Resolve This method contains the logic to resolve any conflict that may occur while replicating an operation from bridge for a key that already exists in the cache. Whenever any conflict occurs, the cache calls BridgeConflictResolution to decide which operation to apply on the cache depending upon rules defined in it. It takes two parameters/entries, both are of ProviderBridgeItem type. ProviderBridgeItem contains the following parameters:
  • BridgeItemVersion contains version of an item (LATEST, OLD, SAME).

  • Key contains key of an item.

  • Value contains value of an item.

  • BridgeItemOpCodes contains conflicted operation (Add, Remove, Update, Clear, RemoveGroup, RegisterKeyNotification).

Sample Implementation of IBridgeConflictResolver Interface

public class Resolver : IBridgeConflictResolver
{
    private bool _enableLogging;
    private TextWriter _textLogger;
    private string streamLog = "bridgeResolverLog.txt"

    public void Dispose()
    {
        if (_enableLogging)
        {
            _textLogger.Close();
        }
    }

    public void Init(System.Collections.IDictionary parameters)
    {
        //Initialize textWriter
        if(parameters.Contains("logging")){
            _enableLogging = Convert.ToBoolean(parameters["logging"]);
        }
        if (_enableLogging){
            _textLogger = new StreamWriter(streamLog);
        }
    }

    public ConflictResolution Resolve(ProviderBridgeItem oldEntry, ProviderBridgeItem newEntry)
    {
        ConflictResolution conflictResolution = new ConflictResolution();
        switch (oldEntry.BridgeItemVersion)
        {
            case BridgeItemVersion.OLD:
            {
               conflictResolution.ResolutionAction = ResolutionAction.ReplaceWithNewEntry;
            }
            break;

            case BridgeItemVersion.LATEST:
            {
                conflictResolution.ResolutionAction = ResolutionAction.KeepOldEntry;
            }
            break;

            case BridgeItemVersion.SAME:
            {
                if (oldEntry.OpCode == BridgeItemOpCodes.Remove){
                    conflictResolution.ResolutionAction = ResolutionAction.ReplaceWithNewEntry;
                }
                else{
                  conflictResolution.ResolutionAction = ResolutionAction.KeepOldEntry;
                }
            }
            break;
        }
        if (_enableLogging){
          //perform operations
        }
        return conflictResolution;
    }
}
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