Don't forget to set ignore_exc when using pymemcache

After upgrading Django to 4.2, we started replacing python-memcached with pymemcache.

Once the switch was done, we noticed that the default setup was no longer behaving well in a high-availability scenario. If multiple memcached backends were configured and one of them went down, any cache-related code could fail with an exception instead of degrading gracefully.

After checking the official documentation, the reason became clear: by default, pymemcache raises exceptions on connection failures unless you explicitly set ignore_exc = True.

So the fix is simply to add that option to your Django CACHES settings:

CACHES = {
    'default': {
        'BACKEND': 'django.core.cache.backends.memcached.PyMemcacheCache',
        'LOCATION': [
            'host1:11211',
            'host2:11211',
        ],
        'OPTIONS': {
            'ignore_exc': True,
        }
    }
}

If you expect memcached nodes to fail independently and still want your application to continue running, this setting is easy to miss but important to have.