Re: replication behind load balancer

[David Alexander <alexandd@xxxxxxxx>]

--On Thursday, March 24, 2005 9:53 PM -0500 Wesley Craig <wes@xxxxxxxxx> 
wrote:

> On 24 Mar 2005, at 10:46, johanna bromberg craig wrote:
> > Also, as a side note, I'm not sure fail over in the clients will
> > work right if both cosign servers are behind a load balancer. I
> > haven't drawn it all out yet, but the basic idea behind client fail
> > over is that the filters ask every weblogin server they are aware
> > of ( A, B, and C ) based on the lookup they did at startup. If they
> > are talking to a load balancer that only had 1 IP/name, they might
> > only get A when in fact B happen to have the most  up-to-date
> > information. Like I said, I haven't really thought about this
> > though, so I might be wrong, too.
>
> You're correct.  My suggested configuration would be to have the load
> balancer only handle HTTP(S) traffic.  In order for filter <->  cosignd
> interactions (include replication and fail over) to function  properly,
> the filters need to have direct access to each of the  cosignd's.

I want to understand more about how cosign replication works.  In the 
scenario described above, it does not seem like cosignd replication has a 
high-availability architecture.  If cosignd on host b has up-to-date info 
that is not propagated to other cosignds, and host b dies, then the 
information is lost.

Our intention was to load balance https and port 6663 traffic. 
Communication between the cosignd processes would occur on the private 
network and would not be load balanced.  If cosignd indeed has replication 
capabilities, it's not clear to me why this wouldn't work.

Has anyone done any work to replace file read/writes with database calls? 
It seems like this would provide a high-availability architecture that 
would be reliable and easy to deploy.

Dave