#22353: CachedStaticFilesMixin lags in updating hashed names of other static
files
referenced in CSS
-------------------------------------+--------------------
Reporter: woodlee | Owner: nobody
Type: Bug | Status: new
Component: contrib.staticfiles | Version: 1.6
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+--------------------
Procedure to replicate:
1. Be using staticfiles with CachedStaticFilesStorage.
2. Have a CSS file such as 'abc.css' which refers to an image file such as
'xyz.png' (via either "url()" or "@import").
3. Do an initial run of collectstatic. Observe correct substitution of the
path to 'xyz.png' to its hashed name within abc.css.
4. Change the contents of xyz.png (maybe it's a sprites file... so changes
aren't unheard of!).
5. Rerun collectstatic (without the --clear option).
6. Observe that abc.css still refers to the old hashed name of xyz.png;
this is the bug.
7. Run collectstatic a third time.
8. Observe that abc.css now refers to the correct, newer hashed name of
xyz.png.
I believe this is happening because during post_process, when the
url_converter calls url() (see
https://github.com/django/django/blob/1.6.2/django/contrib/staticfiles/storage.py#L195),
url() gets the hashed name out of the staticfiles cache... which has not
yet been updated with the new hashed-name value for the image file, since
said cache updating doesn't happen until the end of post_process.
I think the best solution may be to add a kwarg of 'use_cache=True' to
url(), which url_converter can set to False when it calls url(). When
False, the cache will simply be evaded (not updated) and hashed_name can
be called directly. In this way, url_converter is always substituting to
the most up-to-date hash, but actually updating the cache is still delayed
until the end of post_process, which seems desirable since I think
updating that cache should happen as closely as possible in time to the
moment when the new static assets are placed wherever they'll be served
from (bit of a race condition, there).
Unrelated: it would be nice to warn in documentation that if you define a
separate 'staticfiles' cache in CACHES, it might be desirable to set its
TIMEOUT option to None. I kept wondering why lookups were coming back
empty and eventually realized it was because my staticfiles cache was
using the default 5 minute timeout.
--
Ticket URL: <https://code.djangoproject.com/ticket/22353>
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