Django 1.9 removed get_cache from django.core.cache

[grumpa]

Rosetta 0.7.8, Django 1.9. Using memcached backend. Error:

rosetta/poutil.py
from django.core.cache import get_cache
ImportError: cannot import name 'get_cache'

Django 1.9 release notes: django.core.cache.get_cache is removed

[mbi]

Not sure how to trigger that. That code branch is only called for backward compatibility, if the first import in https://github.com/mbi/django-rosetta/blob/develop/rosetta/storage.py#L10 fails. It won't ever be called on Django 1.9, or am I missing something?

[grumpa]

It's me who missed something. I had problems with behavior with web interface so i tried to switch to different cache then the default LocMem. I put MemCached to setting and the problem has begun.
I think now I have improperly configured MemCached. So i apologize.

[mbi]

Sweet, thank you.

[saschwarz]

I'm also getting this error in django 1.9 with rosetta 0.7.11 when I use Memcached cache backend. Here's the full traceback:

Unhandled exception in thread started by <function wrapper at 0x1113932a8>
Traceback (most recent call last):
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/management/commands/runserver.py", line 116, in inner_run
    self.check(display_num_errors=True)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/management/base.py", line 426, in check
    include_deployment_checks=include_deployment_checks,
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/checks/registry.py", line 75, in run_checks
    new_errors = check(app_configs=app_configs)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/checks/urls.py", line 13, in check_url_config
    return check_resolver(resolver)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/checks/urls.py", line 23, in check_resolver
    for pattern in resolver.url_patterns:
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/utils/functional.py", line 33, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/urlresolvers.py", line 417, in url_patterns
    patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/utils/functional.py", line 33, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/urlresolvers.py", line 410, in urlconf_module
    return import_module(self.urlconf_name)
  File "/usr/local/Cellar/python/2.7.8_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/Users/saschwarz/dev/agilitycourses/urls.py", line 44, in <module>
    url(r'^rosetta/', include('rosetta.urls')),
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/conf/urls/__init__.py", line 52, in include
    urlconf_module = import_module(urlconf_module)
  File "/usr/local/Cellar/python/2.7.8_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/rosetta/urls.py", line 2, in <module>
    from .views import (home, list_languages, download_file, lang_sel, translate_text, ref_sel)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/rosetta/views.py", line 18, in <module>
    from rosetta.poutil import find_pos, pagination_range, timestamp_with_timezone
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/rosetta/poutil.py", line 16, in <module>
    from django.core.cache import get_cache
ImportError: cannot import name get_cache

If I remove rosetta from the INSTALLED_APPS I can see is how I've configured CACHES:

$ python manage.py shell --settings=dev_settings
Python 2.7.8 (default, Oct 19 2014, 16:06:28) 
[GCC 4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.40)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from django.conf import settings
>>> settings.CACHES
{'default': {'LOCATION': '127.0.0.1:11211', 'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache'}}
>>> 

If I remove my CACHES definition and add rosetta back into INSTALLED_APPS django starts and runs using the default cache:

$ python manage.py shell --settings=dev_settings
Python 2.7.8 (default, Oct 19 2014, 16:06:28) 
[GCC 4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.40)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from django.conf import settings
>>> settings.CACHES
{'default': {'BACKEND': 'django.core.cache.backends.locmem.LocMemCache'}}
>>> 

I've running this configuration in production using django 1.7 and rosetta 0.7.4 and don't see this error.
In dev I'm working on upgrading to django 1.9 and rosetta 0.7.11 and if I downgrade rosetta to 0.7.4 I also see the traceback at start up. So it appears to be introduced by the API change in django 1.9

Do I have my CACHES misconfigured? Thanks!

[mbi]

Hi @saschwarz. Have you overridden ROSETTA_CACHE_NAME?

I.e. what is the output of this?

from rosetta.conf import settings as rosetta_settings
print(rosetta_settings.ROSETTA_CACHE_NAME)

It should match one of your cache backends, probably default.

[saschwarz]

Thanks for the fast reply! I haven't overridden it:

>>> from rosetta.conf import settings as rosetta_settings
>>> print(rosetta_settings.ROSETTA_CACHE_NAME)
default

[mbi]

Okay interesting, does any of these lines throw an error?

from rosetta.conf import settings as rosetta_settings
from django.core.cache import caches
cache = caches[rosetta_settings.ROSETTA_CACHE_NAME]
print(cache)

[saschwarz]

That gave the answer:

 $ python manage.py shell --settings=dev_settings
Python 2.7.8 (default, Oct 19 2014, 16:06:28) 
[GCC 4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.40)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from rosetta.conf import settings as rosetta_settings
>>> from django.core.cache import caches
>>> cache = caches[rosetta_settings.ROSETTA_CACHE_NAME]
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/cache/__init__.py", line 80, in __getitem__
    cache = _create_cache(alias)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/cache/__init__.py", line 55, in _create_cache
    return backend_cls(location, params)
  File "/Users/saschwarz/.virtualenvs/django19/lib/python2.7/site-packages/django/core/cache/backends/memcached.py", line 159, in __init__
    import memcache
ImportError: No module named memcache

In my new Django 1.9 venv I hadn't installed memcache! I hadn't noticed it because the new rosetta code checked that I had an incompatible cache backend and when I enabled my production backed in dev the ImportError was being caught/handled by: https://github.com/mbi/django-rosetta/blob/develop/rosetta/poutil.py#L12

I guess you could do something to not hide that type of traceback:

try:
    from django.core.cache import caches
    cache = caches[rosetta_settings.ROSETTA_CACHE_NAME]
except ImportError as e:
    try:
        from django.core.cache import get_cache
        cache = get_cache(rosetta_settings.ROSETTA_CACHE_NAME)
    except ImportError:
        if 'No module named' in e.message:
            raise e
        raise

But it could be brittle... or my situation is unusual... I could create a PR if you think this is valuable.

Sorry to have taken your time for my mistake. Thanks so much for all your help debugging this!

[mbi]

In your case the missing memcached exception was swallowed by that ImportError handler, but actually we no longer need that, as Rosetta only supports Django 1.7+ now. I've removed it in c80f2db