hashicorp/nomad · error

missing target group

Error message

missing target group

What it means

ScalingPolicy.validateTargetHorizontal() requires a non-empty `TaskGroup` key in the target map for horizontal policies. The group identifies which task group's count is scaled; omission triggers this error.

Source

Thrown at nomad/structs/structs.go:6472

	return mErr.ErrorOrNil()
}

func (p *ScalingPolicy) validateTargetHorizontal() (mErr multierror.Error) {
	if len(p.Target) == 0 {
		// This is probably not a Nomad horizontal policy
		return
	}

	// Nomad horizontal policies should have Namespace, Job and TaskGroup
	if p.Target[ScalingTargetNamespace] == "" {
		mErr.Errors = append(mErr.Errors, fmt.Errorf("missing target namespace"))
	}
	if p.Target[ScalingTargetJob] == "" {
		mErr.Errors = append(mErr.Errors, fmt.Errorf("missing target job"))
	}
	if p.Target[ScalingTargetGroup] == "" {
		mErr.Errors = append(mErr.Errors, fmt.Errorf("missing target group"))
	}
	return
}

// Diff indicates whether the specification for a given scaling policy has changed
func (p *ScalingPolicy) Diff(p2 *ScalingPolicy) bool {
	copy := *p2
	copy.ID = p.ID
	copy.CreateIndex = p.CreateIndex
	copy.ModifyIndex = p.ModifyIndex
	return !reflect.DeepEqual(*p, copy)
}

func (p *ScalingPolicy) Stub() *ScalingPolicyListStub {
	stub := &ScalingPolicyListStub{
		ID:          p.ID,
		Type:        p.Type,
		Target:      make(map[string]string),

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Add `group = "<task-group-name>"` inside the policy's target block.
2. If the policy is defined inline in the job's scaling block, prefer the inline form so Nomad infers the target keys.
3. For the API path, set Target["TaskGroup"] explicitly in the JSON payload.

Example fix

// before
target {
  namespace = "default"
  job       = "web"
}
// after
target {
  namespace = "default"
  job       = "web"
  group     = "frontend"
}

if policy.Target["TaskGroup"] == "" {
	return fmt.Errorf("horizontal policy target missing TaskGroup")
}

When it happens

Trigger: Submitting a horizontal scaling policy whose target block includes `namespace` and `job` but omits `group`, or an API-created Target map without the ScalingTargetGroup key.

Common situations: Templates that stop at namespace/job; tooling that fills target keys selectively; users assuming the policy's owning group is inferred automatically when written inside the job file (inline scaling blocks infer it, but standalone policy API objects must set it).

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• missing target namespace
• missing target job
• missing scaling policy type
• maximum count must be specified and non-negative
• maximum count must not be less than minimum count

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/517f426096aea71f. Report an issue: GitHub.