MAAS

  1. Bug #1842896
  2. Comment #2

Comment 2 for bug 1842896

Revision history for this message
Pedro Guimarães (pguimaraes) wrote : Re: [VM Provisioning] If constraints: zones=<ZONE> causes Juju to provision new VMs on same node of correct zone in disrespect of overcommit restrictions

Hi John, I am saying that, given a zone constraint, Juju does not pick the other 2 machines on zone-1 to schedule its VMs. It always picks the same node, in disregard of spare resources somewhere else in the same zone.

In short, yes I've done manual tests. Still, I need to say that Juju/MAAS interaction on VM building is kind of a gray area for me.

Looking into MAAS docs, I can only see one VM creation op ("composition" as MAAS calls it):
POST /MAAS/api/2.0/pods/{id}/?op=compose
Where id is the KVM host ("pod") identifier. Here: https://maas.io/docs/api
This is consistent with MAAS cli, in which I always need to point which KVM host I want to build my VM from.

Therefore, I believe Juju is selecting one node to build the VM, which means it is acting as a scheduler.

However, I also believe MAAS is not reporting back a failure whenever it finds out that host has not enough resources or building the new VM will pass its overcommit threshold.

Can you confirm Juju part (i.e. picking one node, always the same)? What would happen if MAAS returns a failure in this case?