[LON-CAPA-admin] Move users live to other access nodes

Stuart Raeburn raeburn at msu.edu
Thu Apr 2 10:15:39 EDT 2015

Hi Maged,

> I am wondering if there is a graceful way to force users off an   
> access node when this happens?

See bug 6771.

I have added a "Switch active users on next access" domain  
configuration to the "User session hosting/offloading" settings for  
domains with more than one server. This switch can be enabled for one  
or more of the domain's servers.

When a server set to switch active users processes a page request, the  
HTML output returned to the browser includes javascript to (a) display  
an alert announcing that the session is about to be transferred, and  
then (b) complete the switch to the least busy server amongst those  
designated to receive offloaded sessions (after five seconds).

Since this happens on page load, it does require the user to be actively
interacting with the system (i.e., the web browser needs to request a page
from the server).

Note: any transactions resulting from the original page request (e.g.,  
grading of a homework submission) will be completed on the server  
before the output containing the server switch function is returned to  
the client.

Stuart Raeburn
LON-CAPA Academic Consortium

Quoting "Abdel Messeh, Maged" <mmesseh at illinois.edu>:

> Hi All,
> We have a problem where occasionally one of our access nodes will   
> get a very high number of apache processes, close to the max allowed  
>  in the configuration which is 150 which consumes most of the 6G   
> memory that each access node has.
> Most recently, I managed to catch one of those incidents and we had:
> 122 apache processes with total memory size of 4G, fortunately this   
> one was only for about 5 min.
> However, I had other cases where it lasted for about 1 hour.
> I am wondering if there is a graceful way to force users off an   
> access node when this happens?  Hence, when trying to login back   
> they could be moved to another access node.
> Many thanks,
> Maged
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