How to Fix Openstack Horizon Dashboard on Centos Stream 9 error: InvalidCacheBackendError

If you have recently deployed Openstack Caracal with RDO Packstack you may run into a problem when you first load the Horizon Dashboard. If you get the “Something went wrong” text instead of the regular login page even though Packstack finished successfully check the following. Try the following:

1. Login to your controller
2. Edit this file: /etc/openstack-dashboard/local_settings

CACHES = {
    'default': {
        'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
        'LOCATION': '127.0.0.1:11211',  # Adjust to your memcached server's address if different
    }
}

3. Replace django.core.cache.backends.memcached.MemcachedCache

4. With django.core.cache.backends.memcached.PyMemcacheCache

It should now look like this:

CACHES = {
    'default': {
        'BACKEND': 'django.core.cache.backends.memcached.PyMemcacheCache',
        'LOCATION': '127.0.0.1:11211',  # Adjust to your memcached server's address if different
    }
}

5. Save and close the file

6. Install pymemcache pip install pymemcache

7. Restart the web server: service httpd restart

You should now be able to login to Horizon. If you have an issue try holding down the function key and tap on 5 or if you have a fancy keyboard… dance on F5 a few times 🙂

The error message you’re encountering is because Django is attempting to use a cache backend that it can’t find or isn’t correctly installed. Specifically, it’s looking for django.core.cache.backends.memcached.MemcachedCache, which is not valid in Django 4.2 since Django removed this particular cache backend.

Happy Stacking!