Every kernel reboot leaks the previous container since symfony/http-kernel 7.4.21 #250

What are you trying to achieve?

Run a large functional suite (~3000 Cest tests, rebootable_client: true) within a fixed memory_limit.

What do you get instead?

Since symfony/http-kernel 7.4.21, every test that triggers a kernel reboot (any test sending a second request) keeps its previous container alive until the process ends. Our suite now exhausts its memory_limit after about 1000 tests.

Kernel::shutdown() now ends with gc_collect_cycles() (symfony/http-kernel 7.4.21, "Release the services of the container when the kernel shuts down"). Connector\Symfony::ensureKernelShutdown() calls $kernel->shutdown() from a closure bound to the old container:

https://github.com/Codeception/module-symfony/blob/main/src/Codeception/Lib/Connector/Symfony.php#L70-L87

The cycle collection therefore runs while the old container is still referenced as the closure's $this. Afterwards that container is never freed: a WeakReference to it stays valid for the rest of the run, even after explicit gc_collect_cycles() calls between tests. No entity manager is retained, only the container.

Measured with one Cest of 28 tests (debug: false), counting the containers that are still alive at the end of the suite through WeakReferences collected on every reboot:

The 3 remaining containers are the one created in _initialize() and the current one.

A change that fixes it for us, keeping the doctrine.connections handling introduced in #244 (the closure bound to the container was also introduced there):

protected function ensureKernelShutdown(): void
{
    $this->kernel->boot();

    $container = $this->kernel->getContainer();
    $connections = Closure::bind(static function (object $container): mixed {
        if (!property_exists($container, 'parameters') || !is_array($container->parameters)) {
            return null;
        }
        $connections = $container->parameters['doctrine.connections'] ?? null;
        unset($container->parameters['doctrine.connections']);

        return $connections;
    }, null, $container::class)($container);
    $oldContainer = WeakReference::create($container);
    unset($container);

    try {
        $this->kernel->shutdown();
    } finally {
        if ($connections !== null && ($container = $oldContainer->get()) !== null) {
            Closure::bind(static function (object $container) use ($connections): void {
                $container->parameters['doctrine.connections'] = $connections;
            }, null, $container::class)($container);
        }
    }
}

Details

• Codeception version: 5.3.7
• codeception/module-symfony: 3.11.0 (main has the same code)
• symfony/http-kernel: 7.4.21 (the gc_collect_cycles() call is the only related change in Kernel::shutdown() since 7.4.20)
• PHP Version: 8.5.9 (ZTS, FrankenPHP image)
• Operating System: Linux (Docker)
• Installation type: Composer
• Suite configuration:

modules:
    enabled:
        - Symfony:
              app_path: 'src'
              environment: 'test'
        - Doctrine:
              depends: Symfony
              cleanup: true
        - REST:
              depends: Symfony
              url: /
    config:
        Symfony:
            rebootable_client: true