[hobbit] Loadbalancing Hobbit Server

[Kauffman, Tom]

>From where I sit, an active hobbit server with a running hot standby
seems to be fairly easy to implement now. I haven't tried to set it up,
but I've looked at the requirements.

I'm currently running this config; I use the hot standby for initial
server testing on new releases and for checking out different bb-hosts
layouts for cosmetic appeal. All my systems know both server addresses.
And the hot standby does everything except network tests and alerting.

All that would need to happen in the event the primary hobbit server
failed would be to update the hobbitlaunch.cfg to enable the network
testing module and the alerting module. And move the IP address of the
webserver. This should be doable with the currently available HA toolset
for Linux (I'll know more in a few weeks -- I've been promised a new
pair of hobbit servers to implement this on).

This does require suitable network bandwidth to run the data to both
systems, and it will require playing with the hobbit checkpoint file so
the failover system will know the proper enable/disable/ack statuses on
restart.

Tom Kauffman
NIBCO, Inc

-----Original Message-----
From: Henrik Stoerner [mailto:henrik at hswn.dk] 
Sent: Tuesday, February 20, 2007 1:53 AM
To: hobbit at hswn.dk
Subject: Re: [hobbit] Loadbalancing Hobbit Server

On Mon, Feb 19, 2007 at 11:36:08PM -0500, Scott Walters wrote:
> 
> Because of the complexity of HA solutions and data integrity, I am not
sure
> the hobbit code is the right place for the logic.  Similar to the
database
> backend, you'll open yourself up to a lot of potential debugging.  I
am a
> keep it simple stupid kinda guy and I am reminded of a saying, "A man
with
> one watch always knows what time it is."
> 
> I'd rather see the hobbit tool improve monitoring, reports, and other
> features that really matter.  Let the HA happen outside of hobbit.

I do try to keep it as simple as possible. The loadbalancing stuff had
almost no impact on the existing code, and if at all possible I'll
isolate this in a separate module so a "normal" single-site setup won't
have to deal with it.

But I do sympathize with your point. You could build a HA Hobbit setup
today using standard tools - shared storage and standard failover
software like the Linux-HA tools - and perhaps that is the best way for
this.

> I also believe you should only cluster/load-balance when one box can't
do
> the job.  

That is the problem I was facing recently, so there was no way to avoid
that.

> Introducing those complexities to increase availability are
> usually counterproductive -- you end up taking your system down
because it's
> so hard to configure/maintain.  And then it usually doesn't work
anyway when
> it's supposed to.

*grin* yes, this was clearly demonstrated in an incident we had last
week at 
work.


Regards,
Henrik


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