invalidate_cms_page_cache() prevents start, if db cachetable is non existent

Precondition: Django CMS App, working, without any Caching.

1. Add simple db cache to settings.py

CACHES = {
    'default': {
        'BACKEND': 'django.core.cache.backends.db.DatabaseCache',
        'LOCATION': 'my_cache_table',
    }
}

1. run manage.py createcachetable

This will result in the error shown in the stacktrace below.

CMS tries to invalidate the cache before the cachetable could be created.

As a workaround it is necessary to:

1. remove all non basic django.* modules from INSTALLED_APPS
2. run manage.py createcachetable
3. readd all the modules again

Stack Trace:

./manage.py createcachetable /usr/local/lib/python3.4/importlib/_bootstrap.py:321: RemovedInDjango19Warning: django.utils.importlib will be removed in Django 1.9. return f(_args, *_kwds)

/usr/local/lib/python3.4/importlib/_bootstrap.py:321: RemovedInDjango19Warning: django.contrib.contenttypes.generic is deprecated and will be removed in Django 1.9. Its contents have been moved to the fields, forms, and admin submodules of django.contrib.contenttypes. return f(_args, *_kwds)

Traceback (most recent call last): File “/usr/local/lib/python3.4/site-packages/django/db/backends/utils.py”, line 64, in execute return self.cursor.execute(sql, params) psycopg2.ProgrammingError: FEHLER: Relation „db_cache_table“ existiert nicht LINE 1: SELECT cache_key, value, expires FROM “db_cache_table” WHERE… ^

The above exception was the direct cause of the following exception:

Traceback (most recent call last): File “./manage.py”, line 10, in <module> execute_from_command_line(sys.argv) File “/usr/local/lib/python3.4/site-packages/django/core/management/init.py”, line 351, in execute_from_command_line utility.execute() File “/usr/local/lib/python3.4/site-packages/django/core/management/init.py”, line 325, in execute django.setup() File “/usr/local/lib/python3.4/site-packages/django/init.py”, line 18, in setup apps.populate(settings.INSTALLED_APPS) File “/usr/local/lib/python3.4/site-packages/django/apps/registry.py”, line 115, in populate app_config.ready() File “/usr/local/lib/python3.4/site-packages/django/contrib/admin/apps.py”, line 22, in ready self.module.autodiscover() File “/usr/local/lib/python3.4/site-packages/django/contrib/admin/init.py”, line 24, in autodiscover autodiscover_modules(‘admin’, register_to=site) File “/usr/local/lib/python3.4/site-packages/django/utils/module_loading.py”, line 74, in autodiscover_modules import_module(‘%s.%s’ % (app_config.name, module_to_search)) File “/usr/local/lib/python3.4/importlib/init.py”, line 109, in import_module return _bootstrap._gcd_import(name[level:], package, level) File “<frozen importlib._bootstrap>”, line 2254, in _gcd_import File “<frozen importlib._bootstrap>”, line 2237, in _find_and_load File “<frozen importlib._bootstrap>”, line 2226, in _find_and_load_unlocked File “<frozen importlib._bootstrap>”, line 1200, in _load_unlocked File “<frozen importlib._bootstrap>”, line 1129, in _exec File “<frozen importlib._bootstrap>”, line 1471, in exec_module File “<frozen importlib._bootstrap>”, line 321, in _call_with_frames_removed File “/usr/local/lib/python3.4/site-packages/cms/admin/init.py”, line 11, in <module> plugin_pool.plugin_pool.discover_plugins() File “/usr/local/lib/python3.4/site-packages/cms/plugin_pool.py”, line 32, in discover_plugins invalidate_cms_page_cache() File “/usr/local/lib/python3.4/site-packages/cms/cache/init.py”, line 69, in invalidate_cms_page_cache version = _get_cache_version() File “/usr/local/lib/python3.4/site-packages/cms/cache/init.py”, line 15, in _get_cache_version version = cache.get(CMS_PAGE_CACHE_VERSION_KEY) File “/usr/local/lib/python3.4/site-packages/django/core/cache/backends/db.py”, line 66, in get “WHERE cache_key = %%s” % table, [key]) File “/usr/local/lib/python3.4/site-packages/django/db/backends/utils.py”, line 79, in execute return super(CursorDebugWrapper, self).execute(sql, params) File “/usr/local/lib/python3.4/site-packages/django/db/backends/utils.py”, line 64, in execute return self.cursor.execute(sql, params) File “/usr/local/lib/python3.4/site-packages/django/db/utils.py”, line 97, in exit six.reraise(dj_exc_type, dj_exc_value, traceback) File “/usr/local/lib/python3.4/site-packages/django/utils/six.py”, line 658, in reraise raise value.with_traceback(tb) File “/usr/local/lib/python3.4/site-packages/django/db/backends/utils.py”, line 64, in execute return self.cursor.execute(sql, params) django.db.utils.ProgrammingError: FEHLER: Relation „db_cache_table“ existiert nicht LINE 1: SELECT cache_key, value, expires FROM “db_cache_table” WHERE…

[julianandrews]

I’m just posting here to note that the correct solution to this bug (and related bugs) is almost certainly to delay hitting the cache until after app load. There are a number of reasons that hitting the cache too early is a bad idea.

[ipmb]

#7269 may provide a workaround for this