Add PhpArrayAdapter to cache metadata

[ossinkine]

I propose to cache metadata using PhpArrayAdapter the same way as serializer or validator in Symfony.
I've added it in my project and got 1-2% speed up on production.

If the communtity approve this, I will create a PR.

[dmaicher]

I think this is done already using recipes?

https://github.com/symfony/recipes/blob/master/doctrine/doctrine-bundle/1.12/config/packages/prod/doctrine.yaml#L6

And cache.system should use PhpArrayAdapter

Edit: actually it uses PhpFilesAdapter

[ossinkine]

This is not entirely true. PhpArrayAdapter is not a typical adapter, you can't just set cache.adapter.php_array or something like that, there is no a such service: https://github.com/symfony/symfony/blob/5.1/src/Symfony/Bundle/FrameworkBundle/Resources/config/cache.xml.

Moreover it should be warmed up before using. Usually it's using in prod env as a decorator above configured adapter and warming up on bootstrap.

[dmaicher]

And you say using PhpArrayAdapter would be faster than using cache.system?

[ossinkine]

I used APCu and PhpArrayAdapter a little bit faster in my environment.

No wonder the Symfony uses it in prod in Validator, Serializer and Annotation components 😉

[nicolas-grekas]

PhpArrayAdapter shouldn't be used if it cannot be warmed up, that's why it's used only for some specific use cases. The reason is that opcache (which is the backend used by PhpArrayAdapter) doesn't support updates without leading to potentially significant reserved yet unused memory.

[ossinkine]

Metadata caching looks like the case when we can use PhpArrayAdapter

[ossinkine]

So what about my proposal? I have an example implementation, do I need to create a PR? Or we don't need this and close the issue?

[ostrolucky]

What's your actual proposal? Cache via PhpArrayAdapter by default, or what? Because that's not very useful when flex recipe overrides that, such change should go there instead.

[ossinkine]

I propose to cache via PhpArrayAdapter always in production environment (actually when debug mode is disabled) and configured cache adapter is used as fallback in PhpArrayAdapter, exactly the same way as it used in symfony validator and serializer components.

[ostrolucky]

The way I see it, this proposal would be accepted, but 2 conditions need to be met:

• Similarly as we have doctrine.orm.metadata_cache_driver configuration, Symfony Validator also used to have framework.validation.cache configuration, which was properly deprecated and removed. I don't see keeping it and ignoring it in production expected behaviour, so I'm up for this proposal, but option should be deprecated.
• As @nicolas-grekas mentioned, this makes sense only if we make sure this cache is warmed up. Please make sure that's the case currently, so we don't have high ratio of cache misses.

[ossinkine]

@ostrolucky I couldn't find any description for branches so I can't decide which branch create PR to?

[ostrolucky]

master, please