Can't Login on backup Continuum server, but can on main server?

I have a Continuum instance with a MongoDB replica set that has been running fine for a couple months now. Today I tried to install a second instance of Continuum and point it to the same replica set. Continuum installed correctly, everything seems to be running, and I can access the login page. However, I can't login with the credentials that work on the other Continuum server. I also tried the default username/password for a new instance, but that did not work either. I looked in the logs and see the error

WARNING - catouser - User.Authenticate : Invalid login attempt - [administrator] bad password.

but I've verified the password works on the other server. What could be stopping me from logging in?

Solution

For security reasons, the Continuum installer generates a random encryption key for every new install. As such, you cannot just install a new Continuum instance and point it at an existing database, as the encryption protocols will not match.

The fix is simple. You will need console access to both the old and the new Continuum instances.

In the "main" server (the one that is working), view /etc/continuum/continuum.yaml and grab the key property.
In the "new" server (the one giving you the error), edit the /etc/continuum/continuum.yaml and update the key with the value from the other config.

You can have multiple Continuum servers pointing at the same database or replica set. However, all instances must have the same key.