Immediate.Cache 0.1.0-preview.3

Immediate.Cache

Immediate.Cache is a collection of classes that simplify caching responses from Immediate.Handlers handlers.

Installing Immediate.Cache

You can install Immediate.Cache with NuGet:

Install-Package Immediate.Cache

Or via the .NET Core command line interface:

dotnet add package Immediate.Cache

Either commands, from Package Manager Console or .NET Core CLI, will download and install Immediate.Cache.

Using Immediate.Cache

Creating a Cache

Create a subclass of ApplicationCacheBase, which will serve as the cache for a particular handler. An example:

[Handler]
public static partial class GetValue
{
	public sealed record Query(int Value);
	public sealed record Response(int Value);

	private static ValueTask<Response> HandleAsync(
		Query query,
		CancellationToken _
	) => ValueTask.FromResult(new Response(query.Value));
}

public sealed class GetValueCache(
	IMemoryCache memoryCache,
	Owned<IHandler<GetValue.Query, GetValue.Response>> ownedHandler
) : ApplicationCacheBase<GetValue.Query, GetValue.Response>(
	memoryCache,
	ownedHandler
)
{
	protected override string TransformKey(GetValue.Query request) =>
		$"GetValue(query: {request.Value})";
}

In this case, the GetValueCache class will serve as a cache for the GetValue IH handler.

Register the Cache with DI

In your Program.cs file:

• Ensure that Memory Cache is registered, by calling:

services.AddMemoryCache();

• Register Owned<> as a singleton

services.AddSingleton(typeof(Owned<>));

• Register your cache service(s) as a singleton(s)

services.AddSingleton<GetValueCache>();

Retrieve Data From the Cache

Using an instance of the GetValueCache class that you have created above, you can simply call:

var response = await cache.GetValue(request, token);

If there is a cached value, it will be returned; otherwise a temporary scope will be used to create the handler and execute it; and the returned value will be stored.

[!NOTE] If simultaneous requests are made while the handler is executing, they will wait for the first handler to complete, rather than executing the handler a second/simultaenous time.

Removing Data From the Cache

Using an instance of the GetValueCache class that you have created above, you can remove cached data by calling:

await cache.RemoveValue(request);

[!NOTE] If a handler is running based on this request, it will be cancelled, and any callers waiting on the results from this handler will experience a CancellationToken cancellation.

Updating Data In the Cache

Using an instance of the GetValueCache class that you have created above, you can assign cached data by calling:

await cache.SetValue(request, response);

[!NOTE] If a handler is running based on this request, it will be cancelled, and any callers waiting on the results from this handler will immediately receive the updated response.