Nomad: spread not respected during node drain

[soreko]

It would be convenient if migrations (e.g., triggered by nomad node drain and governed by the migrate stanza) were able to spread new allocations.

This feature will be useful for us, since it will keep the spread configuration constraints even after draining nodes.

[tgross]

Hi @soreko! Could you maybe walk me through that scenario in a little more detail? I want to make sure I understand what the request is.

[soreko]

Hey @tgross, thanks for replying.

I have 100 allocations, with spread stanza:

spread {
    attribute = "${node.unique.id}"
}

So for 10 nodes, I get 10 allocs per node.
When I'm migrating a node with nomad node drain -enable -self, I'm expecting those node's 10 allocs to be spread according to my spread stanza (10 allocs on the other 9 nodes -> ~1 alloc per node), but I'm resulting with bin-packing

[soreko]

Hey @tgross, I think this is a bug, since spread is not enforced when a drain occurs

[tgross]

Hey @soreko sorry I didn't follow up on your first reply. Yeah, that definitely seems like a bug and I'll get it into our planning to fix.