When configuring the Dashboard part, I came across a problem when trying to login controller/horizon.
The log in /var/log/apache2/error shows:
RuntimeError: Unable to create a new session key. It is likely that the cache is unavailable.
Looked up some websites, I resolved this issue by modifying file /etc/memcached.conf, changed -l 10.145.254.24 to 0.0.0.0
root@controller:~# service apache2 reload
root@controller:~# service memcached restart
It worked. However, according to some sources, this is not the standard way to do, because of some security issue.