[LON-CAPA-admin] Server migration

[Guy Albertelli II]

> > The old server should be kept running until the new server
> > runs stable.
> 
> You cannot have both machines run at the same time connected to the  
> cluster.

I feel compelled to put more info here, the blanket ban is not nuanced
enough for me... :-)

Feel free to live by the above rule... it's generally a very good
idea.

but for more details:

You could configure the new machine as a library server in the
production cluster using the new IP and DNS name and not hurt anything 
because no other machine will talk to you since they won't
recognize the new IP or the DNS name that this server will be using.


Additionally, lon-capa has no problems with multiple library servers in
one domain. (we run a few domains like this in the development cluster
(and 1 production one))

When creating user accounts lon-capa will give you the option of
picking which library server the user account goes to, or you could
let it auto balance the account creation across the machines.


LON-CAPA does _NOT_  work well with
 - multiple library servers in one domain, both thinking they have a
   specific users account

A users lon-capa account must only exist on a single library server.

So if you create a copy of your library server and then got it
connected to the cluster such that other machines could talk to both
computers, you would effectively get random results since some
machines would ask server1 about the user, and some ask server2.

So it's a bad idea to make a copy of the library server and then
connect both to the same cluster since things will go pear-shaped
quickly and badly.


-- 
guy at albertelli.com   0-7-1-6-27,137