[LiveComponent] Optimize LiveComponentStack::getCurrentLiveComponent()

[Kocal]

Q	A
Bug fix?	yes
New feature?	no
Docs?	no
Issues	Fix #...
License	MIT

Using Reflection during runtime is costly. Here I suggest using static caching to prevent unnecessary usages of Reflection.

I've re-used reproducer from #2812, but with 50 rows (otherwise I can't create a Blackfire Profile), and it reduced the rendering time by 200ms, https://blackfire.io/profiles/compare/7aa62248-9332-40b3-b6fa-58756cb17232/graph

EDIT: see #2821 (comment)

[norkunas]

Should this use kernel.reset, or you think it will be a small cache and never releasing memory in worker mode will be imperceptible?

[Kocal]

Should this use kernel.reset, or you think it will be a small cache and never releasing memory in worker mode will be imperceptible?

Oh, that's a good point, I didn't think about it.

I think we are safe here, given this reproducer:

<?php
$componentsCount = 100;
$cache = [];

echo sprintf('Memory usage before: %d MiB', memory_get_peak_usage(true) / 1024 / 1024 ) . PHP_EOL;

for ($i = 0; $i < $componentsCount; $i++) {
    $cache['\App\Twig\Components\ComponentA' . $i] = $i % 2;
}
echo sprintf('Memory usage after: %d MiB', memory_get_peak_usage(true) / 1024 / 1024 ) . PHP_EOL;

1. If you have 100 components (something more realistic) or 1000 components, the memory does not change:

Memory usage before: 2 MiB
Memory usage after: 2 MiB

2. With 10k components, +2 MiB:

Memory usage before: 2 MiB
Memory usage after: 4 MiB

3. And with 100k components (???), only 13 MiB:

Memory usage before: 2 MiB
Memory usage after: 13 MiB

The memory usage is not an issue.

And [] !== (new \ReflectionClass($classname))->getAttributes(AsLiveComponent::class) will always return the exact result between requests (unless you modify your components files without redeploying your app 😅) so that's a win-win, the runtime cache is persisted during a request and also for next requests (when using FrankenPHP worker's mode, Swoole, etc...)!

[Kocal]

I went for another solution, where we can completely shortcut isLiveComponent() call, by storing the static cache in getCurrentLiveComponent().

It gives better results, https://blackfire.io/profiles/compare/8bbc8e11-fbad-4853-bb08-9cbdcb857e50/graph:

[smnandre]

We've been using maps of component names -> stuff in various places for some time now, and they've helped winning major optimizations, while I have not received nor read any downsides.

But more importantly ...

The class is used here, not the name. That means all the anonymous components in a given project count as one.

Finally, I've never heard of a project with a thousand TwigComponent classes for now... and i'm pretty sure there would be a lot of other problems before 😶

[smnandre]

TL;DR; maybe let's see if there is some problem here and we will adapt accordingly :)

(i'm talking about the kernel.reset here, not this PR that is a wonderful "little change-big effect" illustration of @Kocal's work ❤️ )