Bulk Extensible Dependency Usage and Implementation

Note

This feature is only available in NCache Enterprise Edition.

In extensible dependency, each dependency takes time to determine change which might cause expiration lag. With the increase in the number of custom dependencies, expiration on each item takes time because of which some items remain in the cache way past their expiry.

In addition to Extensible Dependency, NCache provides another class called BulkExtensibleDependency. Here, a bulk of custom dependencies are evaluated at the same time. This helps boost the application's performance as the items that have expired are removed from the cache in time. BulkExtensibleDependency is provided at runtime through which user can evaluate data dependencies in bulk and call .Expire() on the dependencies that need to be removed from the cache.

Note

In case your business requirement is a method where an item needs to be individually evaluated instead of in a bulk, then use ExtensibleDependency. Otherwise, you will face performance issues.
Kindly refer to Custom Cache Dependencies to get acquainted with all cache dependency custom methods provided by NCache.

Step 1: Implement BulkExtensibleDependency Class

Pre-Requisites

The class must be implemented as a Class Library (.dll) in Visual Studio. This will be deployed on the NCache cluster.
Install the following NuGet packages in your application:
- Alachisoft.NCache.SDK
To override the BulkExtensibleDependency class, include the following assembly in your application:
- Alachisoft.NCache.Runtime.Dependencies
The class implementing BulkExtensibleDependency must be marked as Serializable along with any other parameters the process code might take in.

[Serializable]
public class BulkDependency : BulkExtensibleDependency
{ 
    // Class parameters 

    public BulkDependency(string connString, int ProductId)
    {
        connection = DriverManager.GetConnection(connString);
        connection.open();
        productID = ProductId;
    }

    private Dictionary<int,int> UnitsInStockStatus(List<int> productIds)
        {
            String queryString = "your_query_here";
            Dictionary<int, int> productsInfo = new Dictionary<int, int>();

            using (var cmd = new SqlCommand(queryString, connection))
            {
                using (SqlDataReader reader = cmd.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        int units = 0;
                        Int32.TryParse(reader["UnitsInStock"].ToString(), out units);
                        productsInfo.Add((int)reader.GetValue(0), units);
                    }
                }
            }
            return productsInfo;
        }
    }

    public override void EvaluateBulk(IEnumerable<BulkExtensibleDependency> dependencies)
    {
        List<BulkDependency> dependencyList = new List<BulkDependency>();
        foreach (BulkDependency bulkDependency in dependencies)
        {
            dependencyList.Add(bulkDependency);
        }

        List<int> productIds = GetOutofStockProducts(dependencyList);
        var productsInfo = UnitsInStockStatus(productIds);

        foreach (BulkDependency bulkDependency in dependencyList)
        {
            if (productsInfo.ContainsKey(bulkDependency.productId))
            {
                if (productsInfo[bulkDependency.productId] != bulkDependency.unitsInStock)
                {
                    bulkDependency.Expire();
                }
            }
        }
    }

    private List<int> GetOutofStockProducts()
    {
        List<int> ProductIDs = new List<int>();

        foreach(BulkDependency bulkDependency in dependencies)
            {
                productIds.Add(bulkDependency.productId);
            }

            return productIds;
        }
        return ProductIDs;
    }

    private Dispose()
    {
        // Dispose off all resources
    }
    // This class is to be deployed on NCache 
}

Note

Don't use this.Expire() to expire an object that isn't valid anymore. Instead, call the .Expire() method on the instance of dependency that needs to be expired. e.g. myDep.Expire()

Step 2: Implement BulkCustomDependencyProvider

To implement Bulk Extensible Dependency provider in your application, use the following code snippet.

Pre-Requisites

Install the following NuGet packages in your application:
- Alachisoft.NCache.SDK
To utilize the APIs, include the following namespaces in your application:
- Alachisoft.NCache.Runtime.Dependencies
- Alachisoft.NCache.Runtime.CustomDependencyProviders
- Alachisoft.NCache.Runtime
- Alachisoft.NCache.Runtime.Exceptions
This should be a class library project using Microsoft Visual Studio.

public class BulkCustomDependencyProvider : ICustomDependencyProvider
{     
    public void Init(IDictionary<string, string> parameters, string cacheName)
    {
        // Initialize cache and class parameters
    }

    public BulkDependency CreateDependency(string key, IDictionary<string, string> dependencyParameters)
    {
        int productId = 0;
        int units = 0;
        string connectionString = "";

        if (dependencyParameters != null)
        {
            if (dependencyParameters.ContainsKey("ProductID"))
                productId = Int32.Parse(dependencyParameters["ProductID"]);

            if (dependencyParameters.ContainsKey("UnitsAvailable"))
                units = Int32.Parse(dependencyParameters["UnitsAvailable"]);

            if (dependencyParameters.ContainsKey("ConnectionString"))
                connectionString = dependencyParameters["ConnectionString"];

            // Create bulk extensible dependency
            BulkDependency dependency = new BulkDependency(connectionString, productId, units);
            return dependency;
        }
    }
    public void Dispose ()
    {
        // Dispose off all resources 
    }
}

Step 3: Deploy Implementation on Cache

Deploy this class and any other dependent assemblies on NCache by referring to Deploy Providers in Administrator's Guide for help.

Step 4: Use Bulk Extensible Dependency

Once bulk extensible dependency class has been implemented and deployed, it is ready to be used in your application.

Pre-Requisites for using Bulk Extensible Dependency

Install the following NuGet packages in your application:
- Alachisoft.NCache.SDK
To utilize the Insert API, include the following namespaces in your application:
- Alachisoft.NCache.Client
- Alachisoft.NCache.Runtime.Dependencies
- Alachisoft.NCache.Runtime.Exceptions
The BulkExtensibleDependency class must be deployed on cache.
The application must be connected to cache before performing the operation.
The cache must be running.
To ensure the operation is fail-safe, it is recommended to handle any exceptions within your application, as explained in Handling Exceptions

The following code shows how to add data into the cache using the Insert() with bulk dependency:

try
{   
    // Specify the connection string
    string connectionString = ConfigurationManager.AppSettings["connectionstring"];

    // Fetch the product to be added to the cache
    Product product = FetchProductFromDB(productId);

    // Specify the unique key of the item
    string key = $"Product:{product.ProductID}";

    // Create a cacheItem
    var cacheItem = new CacheItem(product);

    // Create dictionary for dependency parameters
    IDictionary<string, string> param = new Dictionary<string, string>();
    param.Add("ProductID", products.Id.ToString());
    param.Add("ConnectionString", _connectionString);

    // Create Bulk Extensible Dependency using Provider and Add it to Cache Item 
    CustomDependency customDependency = new CustomDependency(ConfigurationManager.AppSettings["ProviderName"], param);

    cacheItem.Dependency = customDependency;

    // Add cacheItem to the cache with bulk dependency
    cache.Insert(key, cacheItem);
}

catch (OperationFailedException ex)
{
    // Exception can occur due to:
    // Connection Failures
    // Operation Timeout
    // Operation performed during state transfer
}

catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}

Additional Resources

NCache provides sample application for bulk extensible dependency on GitHub.

Bulk Extensible Dependency Usage and Implementation

Note

Note

Step 1: Implement BulkExtensibleDependency Class

Note

Step 2: Implement BulkCustomDependencyProvider

Pre-Requisites

Step 3: Deploy Implementation on Cache

Step 4: Use Bulk Extensible Dependency

Additional Resources

See Also