Feature/charm update question, multiple services per node & jetty

[Clint Byrum]

Excerpts from Andreas Hasenack's message of 2012-09-20 12:46:50 -0700:
> Hash: SHA1
> 
> On 19-09-2012 19:57, Clint Byrum wrote:
> > Can you be more explicit with which services you want to run
> > together on the same machine, and why? If you are using EC2, the
> > instance types are pretty flexible, so it always puzzles me why
> > users want to run, say, MySQL and their app service on the same
> > instance.
> 
> I'm puzzled why it puzzles you :)
> 
> Isn't cost a concern? Peanuts by peanuts, if I deploy something
> regularly to EC2 that is short lived, and I can use one instance
> instead of two, that's half the price.
> 

In the us-east-1 and us-west-2 EC2 regions, a t1.micro costs $15/month,
and an m1.small $57.60.

What useful workload can be shared on an m1.small that could not be
broken up into 4 t1.micros? This also has the benefit that those t1.micros
can then be rebooted into larger instances if your load needs temporary
access to real CPU's.

For MAAS, the need for placement for scaling down work loads does make
sense because of the lack of instance flexibility.

> And I'm not counting the zookeeper instance, which already doubles the
> cost for simple short lived deployments.

Indeed, for the smallest scale, we should make it easier to use node 0
as a compute resource. There is an undocumented way to do it right now,
which is to set placement: local, but this carries the same caveats as
jitsu deploy-to.

I do want this feature, but I'm surprised how often the lack of it is
seen as a show stopper, since it really is just a blocker to scaling
*down*, while juju intrinsically is built to scale up quite smoothly.