calledude / AsyncMemoryCache

Lightweight asynchronous in-memory cache that handles construction and disposal of all your expensive objects

AsyncMemoryCache

A highly configurable cache that aims to improve upon IMemoryCache without relying on it as its backing store.

• Lightweight
• Strongly typed
• Configurable eviction behavior
• Configurable lifetime for cache entries
• Lazy construction of cache object
• Supports asynchronous factories
• Automatic disposal of expired cache entries
• (Optional) Integration with Microsoft.Extensions.DependencyInjection
• (Optional) Integration with Microsoft.Extensions.Logging

Usage

using AsyncMemoryCache;
using AsyncMemoryCache.Extensions;

ILoggerFactory loggerFactory = ...;

var cacheLogger = loggerFactory.CreateLogger<AsyncMemoryCache<string, TheClassToCache>>();

var cacheConfig = new AsyncMemoryCacheConfiguration<string, TheClassToCache>
{
	EvictionBehavior = EvictionBehavior.Default // new DefaultEvictionBehavior(TimeProvider.System, TimeSpan.FromSeconds(45))
};

var cache = AsyncMemoryCache<string, TheClassToCache>.Create(cacheConfig, cacheLogger); // Logger is optional

// The factory is started here, will not block
var cacheEntityReference = cache.GetOrCreate("theKey", async () =>
{
	var createdObject = await ...;
	await Task.Delay(1000);
	return createdObject;
})
.WithSlidingExpiration(TimeSpan.FromHours(12));

// Will block here until the object is created
var theCachedObject = await cache["theKey"]; // Short-hand for await cache["theKey"].CacheEntity.ObjectFactory;

Extending the lifetime of a cached object

Given that

• A cache item exists that is expired
• Above mentioned cache item is currently referenced by some code

The way you deal with this is by using (calling Dispose() on) the CacheEntityReference returned whenever the cache object is accessed As long as at least one CacheEntityReference is alive (i.e. not disposed and still in-scope) the underlying cached object will not be evicted/disposed

// Create a cache entry that expires in 15 seconds
var cacheEntityReference = cache.GetOrCreate("theKey", async () =>
{
	var createdObject = await ...;
	await Task.Delay(1000);
	return createdObject;
})
.WithAbsoluteExpiration(DateTimeOffset.UtcNow.AddSeconds(15));

// do stuff with cache entry that takes longer than 15 seconds

	...

// The underlying cached object is not immediately disposed here, but is now eligible for disposal later on by eviction behaviors (if enabled)
cacheEntityReference.Dispose();