[horde] Memcache server questions

[Steve Devine]

Quoting "Kevin Konowalec" <webadmin at ualberta.ca>:

> That's exactly how it works.  That's why we have a large number of 
> servers so that if one does croak it only affects a small number of 
> users.  I'm not sure if there's a way to get around this.
>
> Now there's a problem we are seeing with it.  Even with all the 
> servers we still have people mysteriously getting kicked off all the 
> time.  I'm not sure if this is a horde bug or if we (still) don't 
> have sufficient "high tide" memcached capacity.  Since I have yet to 
> find any sort of metric we can use to determine how much we'd need 
> for any given load level to prevent overwrites we've just been 
> playing it by ear and adjusting as necessary.
>
> K

I think if the first ip address / hostname in the conf (for memcache servers)  are not the same then people who move from one frontend to another will most certainly get logged out when they are sent to a frontend with a different memcache server assigned to it. The memcache servers do not share the session data. Thats why I believe you either keep them all on one memcache server or devise a way to distribute users to sets of front ends and then don't let them move.  I suppose this could be done with a login server .. but then your login server becomes a single point of failure.
This also makes it harder to pull a front end machine out of the load balancer for service.

>
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> On 13-Nov-08, at 9:31 AM, Steve Devine wrote:
>
>> Quoting "Kevin Konowalec" <webadmin at ualberta.ca>:
>>
>>> Unless I've done something really wrong horde will use a whole whack
>>> of servers if you choose - just add all the ip addresses and ports
>>> comma-seperated in the config tool (or conf.php).  Is that NOT the
>>> case???  I don't believe it is since when once machine goes down all
>>> of a sudden x% of the sessions vanish and my phone starts ringing....
>>>
>>> K
>>
>> Yes exactyl its failover in the sense that the whole thing (Horde) 
>> doesn't crash but all the sessions are lost and everyone is logged 
>> out. When they log back in they get the next server in the config. 
>> At least thats my thinking please someone correct me if I am wrong. 
>> :(
>
>

  

Steve Devine
Email & Storage
Academic Technical Services
Michigan State University

313 Computer Center
East Lansing, MI 48824-1042
1-517-432-7327