Allow specification of a custom job name/prefix for parameterized jobs

[pratheekrebala]

Proposal

Currently, when a parameterized job is dispatched, the jobId of the child job is generated using a fixed template as described here:

nomad/nomad/structs/structs.go

Lines 5398 to 5401 in 49270ed

	func DispatchedID(templateID string, t time.Time) string {
	u := uuid.Generate()[:8]
	return fmt.Sprintf("%s%s%d-%s", templateID, DispatchLaunchSuffix, t.Unix(), u)
	}

When running many versions of a parameterized job, tracking individual dispatches is hard.

I was wondering if it would be possible to allow specifying a optional "prefix" for an individual dispatch or the ability to specify a child job id as a template in the parent parameterized job. e.g.: ffmpeg-parameterized/dispatch-{prefix}-uuid

Use-cases

This would be helpful when using a parameterized job for multiple different clients or tasks, checking status of jobs either through the UI or through the CLI is difficult. Taking the ffmpeg sample task from the docs, this would allow a user to specify which project a specific dispatch might be associated with.

Attempted Solutions

I am currently using metadata fields to track this but this workflow is hard to use through the CLI and through the UI.

[tgross]

Hi @pratheekrebala! Something like this recently came up in an internal discussion and the thing that's somewhat important for a lot of the UX of dispatch jobs is that the names roughly by dispatch time. For small clusters this isn't a big deal but you can imagine that if you had thousands and thousands of dispatches of a job that having the CLI show you an effectively random chunk of them wouldn't be very nice.

That being said, it might be nice as an opt-in feature. It'd have to be a new field in the parameterized block. I'll mark this as an enhancement for roadmapping and also a project that might be good for a new contributor who wants to attempt the jobspec contributing checklist.

[fumblehool]

Hi! @tgross
I've used Nomad and I really Love it!
I would love to work on this if nobody is currently working on this.
Please assign this to me 😄

[tgross]

All yours, @fumblehool! Take a look over the contributing guide and once you've made a PR we'll be happy to review it!

[geovannyAvelar]

@fumblehool I'm so sorry. I worked on this issue without an assignment, my fault. I sent a PR yesterday, but don't worry, go ahead and send your PR. You assigned it first so it's all yours.

[tgross]

Oops, that happens! How about we review #14631 and maybe pull @fumblehool in for comments if they've already started work?

[fumblehool]

No issues @geovannyAvelar.
Fortunately, I was planning to work on the weekend 😅

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