How to schedule X tasks per node

Nomad
1

Here’s what I’m trying to do.

Every time a new node comes online that meets constraints, I want to schedule 2x job tasks on that node. So something similar to a system job but with a count of 2. How can I achieve this with Nomad? And these nodes are always coming online/offline.

Or is the only way to achieve something close to this is go by resource constraints with a large count:

job "my-job" {
  group "my-job" {
    count = 10000
  }
}

However this feels like it smells pretty bad since the UX will complain about a lot of unplaced tasks when I only have 5 nodes that these tasks can be scheduled on.

Any suggestions? Thanks!

2

Note that I cannot do multiple tasks per group since I’m also defining a service within the job. Following up on this, thanks!

3

sound like a task for Nomad pack, where you can use the templating language to add a for loop and use count in that?

4

@brucellino Is that for achieving multiple tasks in a group? I am not sure if that will solve it for me since you can’t route a service to multiple tasks within a group based on what I’ve tested so far. Do you have an example?

5

No, I was thinking more along the lines of templating the whole thing, task and service. Unfortunately, I don’t have an example for you, I’m also only at the beginning of my Nomad Pack journey!

But if I understand correctly, you want to have a few jobs with associated service assigned to run on a newly registered node?

This feels like you need 2 system jobs, not one system job with count 2. Is the reason you’re not running N system jobs because it becomes unwieldy to manage the job spec, or something else?

If you do end up with unplaced tasks, this doesn’t surprise me - they will contend for resources of course, and not being able to place them all immediately sounds like a feature to me