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04.

Adding a Cache Service

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I've got a pretty important new challenge. We're going to be rendering a lot of markdown... and we don't want to do this on every request - it's just too slow. We really need a way to cache the parsed markdown.

Hmm, so caching is yet another tool that we need. If we had a service that was really good at caching a string and letting us fetch it out later, that would be perfect! Fortunately, Symfony comes with a bundle called DoctrineCacheBundle that can give us exactly this.

Enabling DoctrineCacheBundle

First, double-check that you have the bundle in your composer.json file:

65 lines | composer.json
{
// ... lines 2 - 17
"require": {
// ... lines 19 - 22
"doctrine/doctrine-cache-bundle": "^1.2",
// ... lines 24 - 62
}
}

If for some reason you don't, use Composer to download it.

The bundle lives in the vendor/ directory, but it isn't enabled. Do that in the AppKernel class with new DoctrineCacheBundle():

55 lines | app/AppKernel.php
// ... lines 1 - 5
class AppKernel extends Kernel
{
public function registerBundles()
{
$bundles = array(
// ... lines 11 - 19
new Doctrine\Bundle\DoctrineCacheBundle\DoctrineCacheBundle(),
// ... lines 21 - 22
);
// ... lines 24 - 32
}
// ... lines 34 - 53
}

That added a use statement on top of the class... which is great - but I'll move it down to be consistent with everything else. Awesome!

Once you've enabled a bundle, there are usually two more steps: configure it, then use it. And of course, this has its own documentation that'll explain all of this. But guys, we're already getting really good at Symfony. I bet we can figure out how to use it entirely on our own.

1) Configure the Bundle

First, we need to configure the bundle. To see what keys it has, find the terminal and run:

./bin/console config:dump-reference

The list has a new entry: doctrine_cache. Re-run the command with this:

./bin/console config:dump-reference doctrine_cache

Nice! There's our huge configuration example! Ok, ok: I don't expect you to just look at this and instantly know how to use the bundle. You really should read its documentation. But before long, you really will be able to configure new bundles really quickly - and maybe without needing their docs.

Configuring a Cache Service

Now, remember the goal: to get a cache service we can use to avoid processing markdown on each request. When we added KnpMarkdownBundle, we magically had a new service. But with this bundle, we need to configure each service we want.

Open up config.yml and add doctrine_cache. Below that, add a providers key:

77 lines | app/config/config.yml
// ... lines 1 - 72
doctrine_cache:
providers:
// ... lines 75 - 77

Next, the config dump has a name key. This Prototype comment above that is a confusing term that means that we can call this name anything we want. Let's make it my_markdown_cache:

77 lines | app/config/config.yml
// ... lines 1 - 72
doctrine_cache:
providers:
my_markdown_cache:
// ... lines 76 - 77

You'll see how that's important in a second.

Finally, tell Doctrine what type of cache this is by setting type to file_system:

77 lines | app/config/config.yml
// ... lines 1 - 72
doctrine_cache:
providers:
my_markdown_cache:
type: file_system

This is just one of the built-in types this bundle offers: its docs would tell you the others.

And that's it! In the terminal run ./bin/console debug:container and search for markdown_cache:

./bin/console debug:container markdown_cache

Et voila! We have a new service called doctrine_cache.providers.my_markdown_cache. That's the whole point of this bundle: we describe a cache system we want, and it configures a service for that. Now we're dangerous.