Desktop apps won't connect after configuring memory caching

Nextcloud version (eg, 10.0.2): 12.0.3
Operating system and version (eg, Ubuntu 16.04): Ubuntu 16.04
Apache or nginx version (eg, Apache 2.4.25): 2.4
PHP version (eg, 5.6): 5.6

Is this the first time you’ve seen this error?:

Can you reliably replicate it? (If so, please outline steps):
yup. desktop apps won’t login at all

The issue you are facing:
I recently changed my config to configure memory caching in an effort to increase performance.
I read through and added the following to my config.php:
'memcache.local' => '\OC\Memcache\Redis',

after that, logins via the web app become very very slow, and the desktop client won’t log in at all. the desktop app simply states: no connection to nextcloud at [server address]. operation canceled
I’m not sure how to fix this, so your help would be appreciated greatly.


The output of your Nextcloud log in Admin > Logging:
this seems to be the relevant info, I have several errors of this:
OC\HintException: Memcache \OC\Memcache\Redis not available for local cache at /var/www/nextcloud/lib/private/Memcache/Factory.php#96

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

The output of your Apache/nginx/system log in /var/log/____:
there are a lot of files and logs in here, i’m not sure which one you’re after.