in Job.Scale, ensure that new count is within [min,max] configured in scaling policy

CHANGELOG.md

@@ -14,6 +14,7 @@ BUG FIXES:
  * consul/connect: Fixed a bug where in-place upgrade of Nomad client running Connect enabled jobs would panic [[GH-9738](https://github.com/hashicorp/nomad/issues/9738)]
  * template: Fixed multiple issues in template src/dest and artifact dest interpolation [[GH-9671](https://github.com/hashicorp/nomad/issues/9671)]
  * template: Fixed a bug where dynamic secrets did not trigger the template `change_mode` after a client restart. [[GH-9636](https://github.com/hashicorp/nomad/issues/9636)]
+ * scaling: Fixed a bug where job scaling endpoint did not enforce scaling policy min/max [[GH-9761](https://github.com/hashicorp/nomad/issues/9761)]
  * server: Fixed a bug where new servers may bootstrap prematurely when configured with `bootstrap_expect = 0`.
 
 ## 1.0.1 (December 16, 2020)

api/util_test.go

@@ -53,7 +53,7 @@ func testJobWithScalingPolicy() *Job {
 	job.TaskGroups[0].Scaling = &ScalingPolicy{
 		Policy:  map[string]interface{}{},
 		Min:     int64ToPtr(1),
-		Max:     int64ToPtr(1),
+		Max:     int64ToPtr(5),
 		Enabled: boolToPtr(true),
 	}
 	return job

nomad/job_endpoint.go

@@ -1039,6 +1039,20 @@ func (j *Job) Scale(args *structs.JobScaleRequest, reply *structs.JobRegisterRes
 	prevCount := found.Count
 	if args.Count != nil {
 
+		// if there is a scaling policy, check that the new count is within bounds
+		if found.Scaling != nil {
+			if *args.Count < found.Scaling.Min {
+				return structs.NewErrRPCCoded(400,
+					fmt.Sprintf("group count was less than scaling policy minimum: %d < %d",
+						*args.Count, found.Scaling.Min))
+			}
+			if found.Scaling.Max < *args.Count {
+				return structs.NewErrRPCCoded(400,
+					fmt.Sprintf("group count was greater than scaling policy maximum: %d > %d",
+						*args.Count, found.Scaling.Max))
+			}
+		}
+
 		// Lookup the latest deployment, to see whether this scaling event should be blocked
 		d, err := snap.LatestDeploymentByJobID(ws, namespace, args.JobID)
 		if err != nil {

nomad/job_endpoint_test.go

@@ -6705,6 +6705,49 @@ func TestJobEndpoint_Scale_Invalid(t *testing.T) {
 	require.Contains(err.Error(), "should not contain count if error is true")
 }
 
+func TestJobEndpoint_Scale_OutOfBounds(t *testing.T) {
+	t.Parallel()
+	require := require.New(t)
+
+	s1, cleanupS1 := TestServer(t, nil)
+	defer cleanupS1()
+	codec := rpcClient(t, s1)
+	testutil.WaitForLeader(t, s1.RPC)
+	state := s1.fsm.State()
+
+	job, pol := mock.JobWithScalingPolicy()
+	pol.Min = 3
+	pol.Max = 10
+	job.TaskGroups[0].Count = 5
+
+	// register the job
+	err := state.UpsertJob(structs.MsgTypeTestSetup, 1000, job)
+	require.Nil(err)
+
+	var resp structs.JobRegisterResponse
+	scale := &structs.JobScaleRequest{
+		JobID: job.ID,
+		Target: map[string]string{
+			structs.ScalingTargetGroup: job.TaskGroups[0].Name,
+		},
+		Count:          helper.Int64ToPtr(pol.Max + 1),
+		Message:        "out of bounds",
+		PolicyOverride: false,
+		WriteRequest: structs.WriteRequest{
+			Region:    "global",
+			Namespace: job.Namespace,
+		},
+	}
+	err = msgpackrpc.CallWithCodec(codec, "Job.Scale", scale, &resp)
+	require.Error(err)
+	require.Contains(err.Error(), "group count was greater than scaling policy maximum: 11 > 10")
+
+	scale.Count = helper.Int64ToPtr(2)
+	err = msgpackrpc.CallWithCodec(codec, "Job.Scale", scale, &resp)
+	require.Error(err)
+	require.Contains(err.Error(), "group count was less than scaling policy minimum: 2 < 3")
+}
+
 func TestJobEndpoint_Scale_NoEval(t *testing.T) {
 	t.Parallel()
 	require := require.New(t)