[openstack-dev] [magnum] Autoscaling both clusters and containers

Ryan Rossiter rlrossit at linux.vnet.ibm.com
Tue Nov 17 22:03:21 UTC 2015

Hi all,

I was having a discussion with a teammate with respect to container 
scaling. He likes the aspect of nova-docker that allows you to scale 
(essentially) infinitely almost instantly, assuming you are using a 
large pool of compute hosts. In the case of Magnum, if I'm a container 
user, I don't want to be paying for a ton of vms that just sit idle, but 
I also want to have enough vms to handle my scale when I infrequently 
need it. But above all, when I need scale, I don't want to suddenly have 
to go boot vms and wait for them to start up when I really need it.

I saw [1] which discusses container scaling, but I'm thinking we can 
take this one step further. If I don't want to pay for a lot of vms when 
I'm not using them, could I set up an autoscale policy that allows my 
cluster to expand when my container concentration gets too high on my 
existing cluster? It's kind of a case of nested autoscaling. The 
containers are scaled based on request demand, and the cluster vms are 
scaled based on container count.

I'm unsure of the details of Senlin, but at least looking at Heat 
autoscaling [2], this would not be very hard to add to the Magnum 
templates, and we would forward those on through the bay API. (I figure 
we would do this through the bay, not baymodel, because I can see 
similar clusters that would want to be scaled differently).

Let me know if I'm totally crazy or if this is a good idea (or if you 
guys have already talked about this before). I would be interested in 
your feedback.

[2] https://wiki.openstack.org/wiki/Heat/AutoScaling#AutoScaling_API


Ryan Rossiter (rlrossit)

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