[imp] High Availability / Load Balancing

[Noah silva]

If you are truely talking about a -large- number of users, you could just
somehow hash their usernames such that each user gets assugned to one of
the servers.  Once they log in, user X could always get server Y.  This
could even be some sot of preference in LDAP.  

Alternatively, even a single SQL server can have a warm backup running
beside it with failoverd.

 -- noah silva 

On Tue, 17 Dec 2002, robert sand wrote:

> I am already doing it with 3 servers.  The problem does come in with the sql 
> server as being the single point of failure unless you are able to continuously 
> sync the horde database over all servers in the pool of imp servers.  We use a 
> single server not in the imp pool for the sql database.
> 
> Lee wrote:
> 
> > The more i think about it, the more worried I get about the SQL sessions 
> > implementation. Not only does it require an additional dependancy for 
> > horde (we use ldap for prefs), but it more importantly introduces a 
> > single point of failure. Ive been giving this some thought and I think I 
> > have a far more elegant solutions. I'm not an expert on horde's APIs, 
> > but the following seems like it should work:
> > 
> > Get around the sessions problem:
> > 
> > We use DNS round robins to distribute load equally based on DNS 
> > sequentially resolving each of the servers in the round-robin. Although 
> > this continuous round-robin is nice, we could approximate the same 
> > distribution by choosing a server only once (when you first load 
> > http://webmail.myorg.com). When a user then hits the target horde 
> > implementation, horde would rely on the actual server name: 
> > http://webmail1.myorg.com, http://webmail2.myorg.com, or 
> > http://webmail3.myorg.com.
> > 
> > 
> > Get around the attachments problem:
> > 
> > Theoretically, when a user adds an attachment (uploads it), horde could 
> > create an array called attachments[1] = "path/to/file/uploaded" (like 
> > wise for a 2nd, 3rd etc... attachments). When the use then clicks the 
> > send button, the send funtion(s) try to attach the files that are store 
> > on the server. If the files are not there, horde just uses its 
> > attachments array to re-upload the files and attach them.
> > 
> > 
> > I'm really not an expert on horde's APIs, but the above seems like it 
> > should both be easy to implement and provide for 100% load balancing 
> > capability. If you guys agree, I might start taking a stab at 
> > implementing it this week.
> > 
> > Sincerely,
> > Lee
> > 
> > 
> > On Sunday, December 15, 2002, at 11:01 AM, Chuck Hagenbuch wrote:
> > 
> >> Quoting Dominic Ijichi <dom@ijichi.org>:
> >>
> >>> auto_prepend_file = "/opt/data/htdocs/sessionlib/adodb-session.php"
> >>
> >>
> >> FYI, you'll probably get better performance using Horde's SQL session
> >> handler implementation; as it is, you're loading *two* database 
> >> abstraction
> >> libraries all the time...
> >>
> >> -chuck
> >>
> >> -- 
> >> Charles Hagenbuch, <chuck@horde.org>
> >> "People ask me all the time what it will be like living without otters."
> >>  - Google, thanks to Harpers
> >>
> >> -- 
> >> IMP mailing list
> >> Frequently Asked Questions: http://horde.org/faq/
> >> To unsubscribe, mail: imp-unsubscribe@lists.horde.org
> > 
> > 
> > 
> 
> 
> -- 
> Robert Sand.
> mailto:rsand@d.umn.edu
> University of Minnesota, Duluth
> Information Technology Systems and Services
> 144 MWAH
> 218-726-6122        fax 218-726-7674
> 
> "Walk behind me I may not lead, Walk in front of me I may not follow,
>   Walk beside me and we walk together"  UTE Tribal proverb.
> 
> 
> -- 
> IMP mailing list
> Frequently Asked Questions: http://horde.org/faq/
> To unsubscribe, mail: imp-unsubscribe@lists.horde.org
>