Error : The "kernel" service is synthetic, it needs to be set at boot time before it can be used

Question

In our production website, I caught errors with sentry.io.

Since few month I have about 50 time the same error per day, but I never be able to reproduce it myself in local, preproduction, or even in production.

I have no clue what could throw that. I never had a client that reported me this error.

Does anyone knows what it could be?

ErrorException: Uncaught Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: The "kernel" service is synthetic, it needs to be set at boot time before it can be used. in /mnt/www/project/vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/Container.php:334
Stack trace:
#0 /mnt/www/project/app/cache/prod/Container2xhx4bk/appProdProjectContainer.php(11988): Symfony\Component\DependencyInjection\Container->get('kernel')
#1 /mnt/www/project/app/cache/prod/Container2xhx4bk/appProdProjectContainer.php(12085): Container2xhx4bk\appProdProjectContainer->getTemplating_LocatorService()
#2 /mnt/www/project/app/cache/prod/Container2xhx4bk/appProdProjectContainer.php(9670): Container2xhx4bk\appProdProjectContainer->getTwig_LoaderService()
#3 /mnt/www/project/app/cache/prod/Container2xhx4bk/appProdProjectContainer.php(9660): Container2xhx4bk\appProdProjectContainer->getTwigService()
#4 /mnt/www/project/ap
#1 vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/Container.php(334): handleFatalError

Answer 1

You probably tried to get the kernel from the container before booting the kernel. Normally, a Symfony app starts by booting the kernel, then you can get the kernel from the container. Make sure you are booting it.

The kernel sets itself to the container on booting. Source: https://symfony.com/doc/current/service_container/synthetic_services.html