Making Caching Awesome Again

So, I've recently began a new project. It's no where near stable, or even usable. But I think it's a good enough time to introduce it.

It's called CacheGen and it's hosted at bitbucket and BSD licensed.

Basically, it's a T4 template that generates really awesome helpers for caching. It's geared at ASP.Net, but my goal is to make it so it can be used in other ways as well. So, how does it work? You give it a list of specifications for something you want to cache. Let's say you have a string that's really expensive to generate, but doesn't belong in a database. To go on my theme of markdown being slow, let's call it MarkdownTranslation

You tell the T4 template to create a cache item for it like this:

var tmp=new CacheObject
{
  Name="MarkdownTransform",
  ValueType="string";
}
var cache=new CacheGen("Earlz.Example.MyCache");
cache.Items.Add(tmp);
Write(cache.ToString();

And then, you can use the MyCache class like this:

var text=MyCache.MarkdownTransform ?? (MyCache.MarkdownTransform=Markdown.Translate(foobar));

Much much easier. But, there is a flaw in this. It's possible that we could consume double the server resources required for this. This wouldn't be a problem in this case, but imagine a very heavy SQL query or something. This isn't quite what we want when things are really expensive. So, let's use some other fancy syntax

var text=MyCache.MarkdownTransformCache.LockGetOrLoad(()=>Markdown.Translate(foobar));

What this will do instead is raise a flag so that requests for MarkdownTransform will block and during this time, it will execute the expensive code and other threads will sleep. This way, it only gets executed once. And, when it finally gets the results back, the cache will be loaded with it and the other threads will be able to access it. So, instead of computing the expensive thing multiple times, instead we just hold out other requests for a little while so the expensive thing is done only once.

Sure, you can do this same thing with ASP.Net's cache, but how much code would it require for each time you did this? Hence why it's T4. Also, it's completely statically typed. No casting!

Now, what if you wanted to cache the markdown for multiple posts? Or just want to cache entire post objects? Well, I thought of this too:

You'd make the CacheObject like this in T4:

Name="Transforms";
KeyType="ObjectId";
ValueType="BlogPostData";

Then, you could apply the same lock-first type behavior like so:

var post=MyCache.TransformsCache.LockGetOrLoad(objectid, ()=>LoadPost());

Or, if you prefer the (probably safer) possibly execute twice behavior:

var post=MyCache.Transforms[objectid] ?? (MyCache.Transforms[objectid] = LoadPost());

These are the ideas anyway. None of it is actually implemented yet, and a lot more research must be done to ensure that this is a sane way to go about it. But, you can expect to get something similar to this.

Posted: 12/6/2012 5:17:43 AM

Comments

XRumerTest
Hello. And Bye.
3/30/2014 9:19:26 AM

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