hashicorp/nomad · error

Task group scaling policy validation failed: %v

Error message

Task group scaling policy validation failed: %v

What it means

This error is produced during Job validation in nomad/structs/structs.go when a task group's scaling policy (`tg.validateScalingPolicy`) fails validation. Nomad wraps the underlying policy error with 'Task group scaling policy validation failed: %v' and appends it to the job-level multierror. It indicates the scaling block (horizontal scaling for the group) is malformed or inconsistent with the job.

Source

Thrown at nomad/structs/structs.go:7312

		outer := fmt.Errorf("Task group network validation failed: %v", err)
		mErr = multierror.Append(mErr, outer)
	}

	// Validate task group and task services
	if err := tg.validateServices(); err != nil {
		outer := fmt.Errorf("Task group service validation failed: %v", err)
		mErr = multierror.Append(mErr, outer)
	}

	// Validate group service script-checks
	if err := tg.validateScriptChecksInGroupServices(); err != nil {
		outer := fmt.Errorf("Task group service check validation failed: %v", err)
		mErr = multierror.Append(mErr, outer)
	}

	// Validate the scaling policy
	if err := tg.validateScalingPolicy(j); err != nil {
		outer := fmt.Errorf("Task group scaling policy validation failed: %v", err)
		mErr = multierror.Append(mErr, outer)
	}

	// Validate the tasks
	for _, task := range tg.Tasks {
		if err := task.Validate(j.Type, tg); err != nil {
			outer := fmt.Errorf("Task %s validation failed: %v", task.Name, err)
			mErr = multierror.Append(mErr, outer)
		}
	}

	return mErr.ErrorOrNil()
}

func (tg *TaskGroup) validateNetworks() error {
	var mErr multierror.Error
	portLabels := make(map[string]string)
	// host_network -> static port tracking

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Read the wrapped '%v' detail in the error to identify the exact policy field that failed
2. Fix the scaling block so min <= count <= max and all values are non-negative integers
3. Remove the scaling block from job types that do not support scaling (e.g. system scheduler jobs)
4. Validate the job spec with `nomad job validate <file>` before submitting
5. Upgrade/downgrade Nomad client/agent versions so server and spec fields match

Example fix

// before
task "web" {}
scaling {
  min = -1
  max = 0
}
// after
scaling {
  min = 1
  max = 10
  policy {
    cooldown            = "1m"
    check_idle_delay    = "30s"
  }
}

func validateScalingBlock(j *api.Job) error {
  var errs error
  for _, tg := range j.TaskGroups {
    if tg.Scaling == nil { continue }
    s := tg.Scaling
    if s.Min == nil || s.Max == nil { errs = multierror.Append(errs, fmt.Errorf("group %s: scaling min/max required", *tg.Name)); continue }
    if *s.Min < 0 { errs = multierror.Append(errs, fmt.Errorf("group %s: scaling min negative", *tg.Name)) }
    if *s.Max < *s.Min { errs = multierror.Append(errs, fmt.Errorf("group %s: scaling max < min", *tg.Name)) }
  }
  return errs
}
// run before submitting: nomad job validate <file>

func hasValidScaling(tg *api.TaskGroup) bool {
  return tg.Scaling != nil && tg.Scaling.Min != nil && tg.Scaling.Max != nil &&
    *tg.Scaling.Min >= 0 && *tg.Scaling.Max >= *tg.Scaling.Min
}

When it happens

Trigger: Submitting (job register/plan) a job whose task group has a `scaling` block that: has a negative or non-integer min/max, has max < min, missing required fields, invalid policy `policy` map (e.g. unsupported keys or bad target), or scaling policy on a system/batch job type where scaling is not allowed.

Common situations: Hand-writing HCL with a scaling block and typos in min/max; automating scaling config generation (Terraform nomad_job, CI pipelines) that emits invalid bounds; applying job specs written for newer Nomad versions with fields the current server doesn't accept; adding scaling to a system job.

Related errors

• Task group %s validation failed: %v
• Job type %q does not allow update block
• Job type %q does not allow migrate block
• Task %s validation failed: %v
• Scaling policy invalid: %s

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/47e1e83a7fd4fc38. Report an issue: GitHub.