README.md

FusionCache

FusionCache is an easy to use, high performance and robust cache with an optional distributed 2nd layer and some advanced features.

It was born after years of dealing with all sorts of different types of caches: memory caching, distributed caching, http caching, CDNs, browser cache, offline cache, you name it. So I've tried to put togheter these experiences and came up with FusionCache.

It uses a memory cache (any impl of the standard IMemoryCache interface) as the primary backing store and optionally a distributed, 2nd level cache (any impl of the standard IDistributedCache interface) as a secondary backing store for better resilience and higher performance, for example in a multi-node scenario or to avoid the typical effects of a cold start (initial empty cache, maybe after a restart).

FusionCache also includes some advanced features like a fail-safe mechanism, concurrent factory calls optimization for the same cache key, fine grained soft/hard timeouts with background factory completion, customizable extensive logging and more (see below).

If you want to get yourself comfortable with the overall concepts there's 🦄 A Gentle Introduction available.

If you want to see what you can achieve from start to finish with FusionCache, there's a 🏆 Step By Step guide.

If instead you want to start using it immediately there's a ⭐ Quick Start for you.

✔️ Features

These are the key features of FusionCache:

• 🚀 Optimized factory calls: using the optimized GetOrSet[Async] method prevents multiple concurrent factory calls per key, with a guarantee that only 1 factory will be called at the same time for the same key. This avoids overloading the data source when no data is in the cache or when a cache entry expires (read more)
• 🔀 Optional 2nd level: FusionCache can transparently handle an optional 2nd level cache: anything that implements the standard IDistributedCache interface is supported like Redis, Memcached, MongoDB, SqlServer, etc (read more)
• 💣 Fail-Safe: enabling the fail-safe mechanism prevents throwing an exception when a factory or a distributed cache call would fail, by reusing an expired entry as a temporary fallback, all transparently and with no additional code required (read more)
• ⏱️ Soft/Hard timeouts: advanced timeouts management prevents waiting for too long when calling a factory or the distributed cache. This is done to avoid that such slow calls would hang your application. It is possible to specify both soft and hard timeouts that will be used depending on whether there's a fallback value to use for the specific call or not (read more)
• 🕶️ Background factory completion: when you specify a factory timeout and it actually occurs, the timed-out factory can keep running in the background and, if and when it successfully complete, the cache will be immediately updated with the new value to be used right away (read more)
• ⚡ High performance: FusionCache is optimized to minimize CPU usage and memory allocations to get better performance and lower the cost of your infrastructure all while obtaining a more stable, error resilient application
• 💫 Natively sync/async: full native support for both the synchronous and asynchronous programming model, with sync/async methods working togheter harmoniously
• 📃 Extensive logging: comprehensive, structured, detailed and customizable logging via the standard ILogger<T> interface (you can use Serilog, NLog, etc)

Also, FusionCache has some other nice additional features:

• Portable: targets .NET Standard 2.0
• Null caching: explicitly supports caching of null values differently than "no value". This creates a less ambiguous usage, and typically leads to better performance because it avoids the classic problem of not being able to differentiate between "the value was not in the cache, go check the database" and "the value was in the cache, and it was null"
• Distributed cache circuit-breaker: it is possible to enable a simple circuit-breaker for when a distributed cache becomes temporarily unavailable. This will prevent the distributed cache to be hit with an additional load of requests (that would probably fail anyway) in a problematic moment, so it can gracefully get back on its feet. More advanced scenarios can be covered using a dedicated solution, like Polly
• Dynamic Jittering: setting JitterMaxDuration will add a small randomized extra duration to a cache entry's normal duration. This is useful to prevent variations of the Thundering Herd problem in a multi-node scenario
• Hot Swap: supports thread-safe changes of the entire distributed cache implementation (add/swap/removal)
• Code comments: every property and method is fully documented in code, with useful informations provided via IntelliSense or similar technologies
• Fully annotated for nullability: every usage of nullable references has been annotated for a better flow analysis by the compiler

📦 Distribution

Available packages on Nuget:

Package Name	Release (NuGet)
ZiggyCreatures.FusionCache
ZiggyCreatures.FusionCache.Serialization.NewtonsoftJson
ZiggyCreatures.FusionCache.Serialization.SystemTextJson

⭐ Quick Start

FusionCache can be installed via the nuget UI (search for the ZiggyCreatures.FusionCache package) or via the nuget package manager console:

PM> Install-Package ZiggyCreatures.FusionCache

As an example, imagine having a method that retrieves a product from your database:

Product GetProductFromDb(int id) {
	// YOUR DATABASE CALL HERE
}

💡 This is using the sync programming model, but it would be equally valid with the newer async one for even better performance.

To start using FusionCache the first thing is create a cache instance:

var cache = new FusionCache(new FusionCacheOptions());

If instead you are using DI (Dependency Injection) use this:

services.AddFusionCache();

We can also specify some global options, like a default FusionCacheEntryOptions object to serve as a default for each call we'll make, with a duration of 2 minutes and a Low priority:

var cache = new FusionCache(new FusionCacheOptions() {
	DefaultEntryOptions = new FusionCacheEntryOptions {
		Duration = TimeSpan.FromMinutes(2),
		Priority = CacheItemPriority.Low
	}
});

Or, using DI, like this:

services.AddFusionCache(options => {
	options.DefaultEntryOptions = new FusionCacheEntryOptions {
		Duration = TimeSpan.FromMinutes(2),
		Priority = CacheItemPriority.Low
	}
});

Now, to get the product from the cache and, if not there, get it from the database in an optimized way and cache it for 30 sec simply do this:

var id = 42;

cache.GetOrSet<Product>(
	$"product:{id}",
	_ => GetProductFromDb(id),
	TimeSpan.FromSeconds(30)
);

That's it 🎉

A little bit more

Now, imagine we want to do the same, but also:

• set the priority of the cache item to High (mainly used in the underlying memory cache)
• enable fail-safe for 2 hours, to allow an expired value to be used again in case of problems with the database (read more)
• set a factory soft timeout of 100 ms, to avoid too slow factories crumbling your application when there's a fallback value readily available (read more)
• set a factory hard timeout of 2 sec, so that, even if there is no fallback value to use, you will not wait undefinitely but instead an exception will be thrown to let you handle it however you want (read more)

To do all of that we simply have to change the last line (reformatted for better readability):

cache.GetOrSet<Product>(
	$"product:{id}",
	_ => GetProductFromDb(id),
	// THIS IS WHERE THE MAGIC HAPPENS
	options => options
		.SetDuration(TimeSpan.FromSeconds(30))
		.SetPriority(CacheItemPriority.High)
		.SetFailSafe(true, TimeSpan.FromHours(2))
		.SetFactoryTimeouts(TimeSpan.FromMilliseconds(100), TimeSpan.FromSeconds(2))
);

Basically, on top of specifying the cache key and the factory, instead of specifying just a duration as a TimeSpan we specify a FusionCacheEntryOptions object - which contains all the options needed to control the behaviour of FusionCache during each operation - in the form of a lambda that automatically duplicates the default entry options defined before (to copy all our defaults) while giving us a chance to modify it as we like for this specific call.

Now let's say we really like these set of options (priority, fail-safe and factory timeouts) and we want them to be the overall defaults, while keeping the ability to change something on a per-call basis (like the duration).

To do that we simply move the customization of the entry options to the DefaultEntryOptions in the snippet where we created the FusionCache instance, to something like this:

var cache = new FusionCache(new FusionCacheOptions() {
	DefaultEntryOptions = new FusionCacheEntryOptions()
		.SetDuration(TimeSpan.FromMinutes(2))
		.SetPriority(CacheItemPriority.High)
		.SetFailSafe(true, TimeSpan.FromHours(2))
		.SetFactoryTimeouts(TimeSpan.FromMilliseconds(100), TimeSpan.FromSeconds(2))
});

Now these options will serve as the cache-wide default, usable in every method call as a "starting point".

Then, we just change our method call to simply this:

var id = 42;

cache.GetOrSet<Product>(
	$"product:{id}",
	_ => GetProductFromDb(id),
	options => options.SetDuration(TimeSpan.FromSeconds(30))
);

The DefaultEntryOptions we did set before will be duplicated and only the duration will be changed for this call.

📖 Documentation

The documentation is available in the 📂 docs folder, with:

• 🦄 A Gentle Introduction: what you need to know first
• 🔀 Cache Levels: a bried description of the 2 available caching levels and how to setup them
• 🚀 Factory Call Optimization: no more overloads during a cold start or after an expiration
• 💣 Fail-Safe: an explanation of how the fail-safe mechanism works
• 🎚️ Options: everything about the available options, both cache-wide and per-call
• ⏱️ Timeouts: the various types of timeouts at your disposal (calling a factory, using the distributed cache, etc)
• 🏆 Step By Step: a complete step by step example of why a cache is useful, why FusionCache could be even more so, how to apply most of the options available and what results you can expect to obtain

🧰 Supported Platforms

FusionCache targets .NET Standard 2.0, so any compatible .NET implementation is fine.

NOTE: if you are running on .NET Framework 4.6.1 and want to use .NET Standard packages Microsoft suggests to upgrade to .NET Framework 4.7.2 or higher (see the .NET Standard Documentation) to avoid some known dependency issues.

🖼️ Logo

The logo is an original creation and is a sloth because, you know, speed is very important in a cache 😏 .

💰 Funding / Support

Nothing to do here.

After years of using a lot of open source stuff for free, this is just me trying to give something back to the community.
If you find FusionCache useful please just ✉️ drop me a line, I would be interested in knowing about your usage.

And if you really want to talk about money, please consider making ❤️ a donation to a good cause of your choosing, and maybe let me know about that.

🆎 Comparisons / Benchmarks

Coming Soon

💼 But is it Production Ready ™️ ?

Even though the current version is 0.X for an excess of caution, FusionCache is already used in production on multiple real world projects happily handling millions of requests per day (at least these are the projects I'm aware of).

And again, if you are using it please ✉️ drop me a line, I'd like to know!