hashicorp/nomad · error

PreventRescheduleOnLost is deprecated and ignored in favor o

Error message

PreventRescheduleOnLost is deprecated and ignored in favor of Disconnect.Replace

What it means

TaskGroup.Validate rejects the deprecated task-group field PreventRescheduleOnLost. Its behavior was replaced by the `disconnect { replace = ... }` field, so any job still setting it fails validation. It is appended to the same multierror as the other deprecated disconnect-related fields.

Source

Thrown at nomad/structs/structs.go:7661

	if u := tg.Update; u != nil {
		// Check the counts are appropriate
		if tg.Count > 1 && u.MaxParallel > tg.Count && !(j.IsMultiregion() && tg.Count == 0) {
			mErr.Errors = append(mErr.Errors,
				fmt.Errorf("Update max parallel count is greater than task group count (%d > %d). "+
					"A destructive change would result in the simultaneous replacement of all allocations.", u.MaxParallel, tg.Count))
		}
	}

	if tg.MaxClientDisconnect != nil {
		mErr.Errors = append(mErr.Errors, errors.New("MaxClientDisconnect is deprecated and ignored in favor of Disconnect.LostAfter"))
	}

	if tg.StopAfterClientDisconnect != nil {
		mErr.Errors = append(mErr.Errors, errors.New("StopAfterClientDisconnect is deprecated and ignored favor of Disconnect.StopOnClientAfter"))
	}

	if tg.PreventRescheduleOnLost {
		mErr.Errors = append(mErr.Errors, errors.New("PreventRescheduleOnLost is deprecated and ignored in favor of Disconnect.Replace"))
	}

	// Warn about unbounded rescheduling which may cause thrashing if tasks have
	// unlimited attempts and a low delay.
	//
	// The 5 second gate on the delay is used as this was the previous minimum
	// value which did not produce a warning. It therefore feels like the right
	// gate to use.
	if rp := tg.ReschedulePolicy; rp != nil && rp.Unlimited && rp.Delay < 5*time.Second {
		mErr.Errors = append(
			mErr.Errors,
			errors.New("Reschedule policy has unlimited attempts enabled and a low delay; reschedule thrashing possible"),
		)
	}

	// Check for mbits network field
	if len(tg.Networks) > 0 && tg.Networks[0].MBits > 0 {
		mErr.Errors = append(mErr.Errors, fmt.Errorf("mbits has been deprecated as of Nomad 0.12.0. Please remove mbits from the network block"))

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Remove prevent_reschedule_on_lost from the task group.
2. Add `disconnect { replace = true }` (or false) to express the same intent.
3. Validate the job with `nomad job validate` before submitting.

Example fix

// before
group "batch" {
  prevent_reschedule_on_lost = true
}
// after
group "batch" {
  disconnect {
    replace = true
  }
}

if strings.Contains(jobHCL, "prevent_reschedule_on_lost") {
  return errors.New("deprecated field prevent_reschedule_on_lost; use disconnect { replace }")
}

func usesPreventRescheduleOnLost(tg *structs.TaskGroup) bool {
  return tg.PreventRescheduleOnLost
}

When it happens

Trigger: Submitting a job whose group sets `prevent_reschedule_on_lost = true` (or false) on a Nomad version where the disconnect block supersedes it.

Common situations: Old job files carried forward across upgrades; documentation or modules generated before the disconnect block existed.

Related errors

• StopAfterClientDisconnect is deprecated and ignored favor of
• Disconnect cannot be configured with both lost_after and sto
• lost_after cannot be a negative duration
• stop_after cannot be a negative duration
• Missing job ID

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/5ccfede6f8819160. Report an issue: GitHub.