File removal race condition in FileSystemStorage

[Aymeric Augustin]

#16082 describes a race condition in directory creation. It was fixed, however, the same race condition still exists in the file removal code, a few lines below.

While this bug is unlikely to show up in production, it's probably worth fixing in the same way, for the sake of consistency and robustness.

Attached patch proposes a fix similar to r16280. Also, it improves slightly the test case added at that revision.

[Pi Delport]

Looks good! Thank you. :)

[Jannis Leidel]

In [16287]:

Fixed #16108 -- Fixed another race condition in the FileSystemStorage backend with regard to deleting a file. Refs #16082, too. Thanks, Aymeric Augustin.

[Mark Lavin]

I know this is fixed in trunk but for what it's worth I have seen this multiple times in production this week. We are using django-compressor for our CSS and JS which delete files in get_available_name ​https://github.com/jezdez/django_compressor/blob/develop/compressor/storage.py#L36. When new CSS/JS is deployed there is a race to create the new cached files and this error appears.

[Jannis Leidel]

Thanks for reporting that, would you mind to opening a ticket in the django_compressor issue tracker, too?

[Pi Delport]

Can this (and #16082) be included for 1.3.2?

(Is there process to follow to request this, for release management?)

[Mark Lavin]

Added django_compressor issue: ​https://github.com/jezdez/django_compressor/issues/159

[daniel@…]

+1 for getting this into 1.3.2. I've also seen this in production with django_compressor.

[Matt C]

Why is the:

    if os.path.exists(name):

...line needed?

That line tells me that an exception should not be raised if the file does not exist and yet in the except clause, an exception is raised if the file was deleted before this thread could do it.

Why the mixed messages and why can't we just have this:

try:
    os.remove(name)
except OSError:
    pass

?