[Console][DI] Fail gracefully

[nicolas-grekas]

Q	A
Branch?	3.4
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	symfony/flex#212, #25280
License	MIT
Doc PR	-

I already experienced this issue a few times without spending time digging it:
sometimes, you call cache:clear, and the command quits without any output, and with 255 status code.

The reason is the @include in Kernel, which makes everything silent, especially fatal errors (thanks PHP...)
So if the to-be-removed container is broken for some fatal reason, the failure is really bad.

To fix that, here are two measures:

• use include_once instead of require_once in the dumped container: that's OK there to actually not immediately load the file, any hard failure will happen later anyway, and any soft failure will allow the cache:clear command to complete (like when you remove a package)
• register Application::renderException() as the main PHP exception handler, via Debug::ErrorHandler when it's available

End result when it fails:

instead of a blank output.

[theofidry]

@nicolas-grekas so you would still get a silent hard failure if you do c:c --env prod?

[nicolas-grekas]

Not since 10 minutes. When did you read the code ? :)

[theofidry]

I didn't, but I have trouble following :P

[weaverryan]

Fwiw, I believe a user on Twitter hit the same issue - when removing Twig https://twitter.com/neelion333/status/936623941937795072 - looks very easy to reproduce

[weaverryan]

I think this bug might be quite critical. I think I'm even able to hit it through the web interface. While upgrading a project from 3.3 to 3.4, I did the following:

1. Added the container.autowiring.strict_mode: true parameter.
2. Refreshed to rebuild the container
3. Removed this parameter
4. Refreshed to this error:

@nicolas-grekas Do you think it's related? Do you need me to try to create a repeater (the above was done on our big KnpU Symfony 3 tutorial project).

[nicolas-grekas]

@weaverryan looks like the same yes.

I improved the behavior by replacing the nasty @-silencing by a specific E_WARNING silencing. The container-loading file is also now resilient to a broken container folder, by using include+return in case of failure. Also handled by Kernel.

PR is ready. Dunno how to test it as the behavior is triggered by edge case fatal errors...

[fabpot]

Thank you @nicolas-grekas.

[weaverryan]

I do not appear to be able to trigger the fatal error anymore. I think you may have gotten it!

[k00ni]

I experienced this bug today using Symfony 4.0.6. It occurs in certain controller actions and not when using the cache commands via terminal. But these actions call indirectly cache->clear() which seem to interfere with symfony internals?

FatalErrorException Compile Error: Container Failed opening required [...]getRouting_LoaderService.php' (include_path='.:/usr/local/lib/php') in srcDevDebugProjectContainer.php (line 295)

I was able to "fix" that for now, by removing the WebProfilerBundle resp. ProfilerPack:

• "symfony/profiler-pack": "^1.0"
• "symfony/web-profiler-bundle": "^4.0.6"

Afterwards i cleared the cache using rm -rf var/cache/* and it seems to work.

EDIT: See #25255 (comment) for updates to the WebProfilerBundle.

[nicolas-grekas]

What are you calling in your controller?

[k00ni]

Here is part of the code:

$env = /* .. */;
$cache = new FilesystemCache('', 0, __DIR__.'/../../var/cache/'.$env);

// do some mysql operations

$cache->clear();

I expected the cache, because you mentioned it at the beginning. Furthermore, it tried to load something from the cache folder, which could not be opened.

FatalErrorException Compile Error: Container Failed opening required [...]getRouting_LoaderService.php' (include_path='.:/usr/local/lib/php') in srcDevDebugProjectContainer.php (line 295)

[k00ni]

Ok, i changed $cache->clear() to a solution which directly removes entries, which my app created. I re-enabled the WebProfilerBundle and tried the mentioned controller actions. And it worked. I assume, that calling $cache->clear() in a controller was the problem?

[nicolas-grekas]

I suppose. FilesystemCache is not made for clearing the full Symfony cache AFAIK.