changes to make sure that Max is present and valid, to improve error …

…messages

* made api.Scaling.Max a pointer, so we can detect (and complain) when it is neglected
* added checks to HCL parsing that it is present
* when Scaling.Max is absent/invalid, don't return extraneous error messages during validation
* tweak to multiregion handling to ensure that the count is valid on the interpolated regional jobs

resolves #8355

api/scaling.go

@@ -56,7 +56,7 @@ type ScalingPolicy struct {
 	Namespace   string
 	Target      map[string]string
 	Min         *int64
-	Max         int64
+	Max         *int64
 	Policy      map[string]interface{}
 	Enabled     *bool
 	CreateIndex uint64

command/agent/scaling_endpoint.go

@@ -78,10 +78,15 @@ func (s *HTTPServer) scalingPolicyQuery(resp http.ResponseWriter, req *http.Requ
 func ApiScalingPolicyToStructs(count int, ap *api.ScalingPolicy) *structs.ScalingPolicy {
 	p := structs.ScalingPolicy{
 		Enabled: *ap.Enabled,
-		Max:     ap.Max,
 		Policy:  ap.Policy,
 		Target:  map[string]string{},
 	}
+	if ap.Max != nil {
+		p.Max = *ap.Max
+	} else {
+		// catch this in Validate
+		p.Max = -1
+	}
 	if ap.Min != nil {
 		p.Min = *ap.Min
 	} else {

jobspec/parse_group.go

@@ -364,6 +364,9 @@ func parseScalingPolicy(out **api.ScalingPolicy, list *ast.ObjectList) error {
 	if err := dec.Decode(m); err != nil {
 		return err
 	}
+	if result.Max == nil {
+		return fmt.Errorf("missing 'max'")
+	}
 
 	// If we have policy, then parse that
 	if o := listVal.Filter("policy"); len(o.Items) > 0 {

nomad/structs/structs.go

@@ -5948,19 +5948,21 @@ func (tg *TaskGroup) validateScalingPolicy(j *Job) error {
 
 	var mErr multierror.Error
 
-	if tg.Scaling.Min > tg.Scaling.Max {
+	// was invalid or not specified; don't bother testing anything else involving max
+	if tg.Scaling.Max < 0 {
+		mErr.Errors = append(mErr.Errors,
+			fmt.Errorf("Scaling policy invalid: maximum count must be specified and non-negative"))
+	} else if tg.Scaling.Max < tg.Scaling.Min {
 		mErr.Errors = append(mErr.Errors,
 			fmt.Errorf("Scaling policy invalid: maximum count must not be less than minimum count"))
-	}
-
-	if int64(tg.Count) < tg.Scaling.Min && !(j.IsMultiregion() && tg.Count == 0) {
+	} else if tg.Scaling.Max < int64(tg.Count) {
 		mErr.Errors = append(mErr.Errors,
-			fmt.Errorf("Scaling policy invalid: task group count must not be less than minimum count in scaling policy"))
+			fmt.Errorf("Scaling policy invalid: task group count must not be greater than maximum count in scaling policy"))
 	}
 
-	if tg.Scaling.Max < int64(tg.Count) {
+	if int64(tg.Count) < tg.Scaling.Min && !(j.IsMultiregion() && tg.Count == 0 && j.Region == "global") {
 		mErr.Errors = append(mErr.Errors,
-			fmt.Errorf("Scaling policy invalid: task group count must not be greater than maximum count in scaling policy"))
+			fmt.Errorf("Scaling policy invalid: task group count must not be less than minimum count in scaling policy"))
 	}
 
 	return mErr.ErrorOrNil()