rpc: set the job scale eval priority to the job priority.

Previously the eval priority was set to the default priority
rather than the priority configured within the target job. This
change fixes this bug, ensuring any eval created as a result of
scaling uses the job priority.

nomad/job_endpoint.go

@@ -1129,7 +1129,7 @@ func (j *Job) Scale(args *structs.JobScaleRequest, reply *structs.JobRegisterRes
 			eval := &structs.Evaluation{
 				ID:             uuid.Generate(),
 				Namespace:      namespace,
-				Priority:       structs.JobDefaultPriority,
+				Priority:       job.Priority, // Safe as nil check performed above.
 				Type:           structs.JobTypeService,
 				TriggeredBy:    structs.EvalTriggerScaling,
 				JobID:          args.JobID,

nomad/job_endpoint_test.go

@@ -6985,6 +6985,57 @@ func TestJobEndpoint_Scale_NoEval(t *testing.T) {
 	require.Equal(int64(originalCount), events[groupName][0].PreviousCount)
 }
 
+func TestJobEndpoint_Scale_Priority(t *testing.T) {
+	t.Parallel()
+	requireAssertion := require.New(t)
+
+	s1, cleanupS1 := TestServer(t, nil)
+	defer cleanupS1()
+	codec := rpcClient(t, s1)
+	testutil.WaitForLeader(t, s1.RPC)
+	fsmState := s1.fsm.State()
+
+	// Create a job and alter the priority.
+	job := mock.Job()
+	job.Priority = 90
+	originalCount := job.TaskGroups[0].Count
+	err := fsmState.UpsertJob(structs.MsgTypeTestSetup, 1000, job)
+	requireAssertion.Nil(err)
+
+	groupName := job.TaskGroups[0].Name
+	scale := &structs.JobScaleRequest{
+		JobID: job.ID,
+		Target: map[string]string{
+			structs.ScalingTargetGroup: groupName,
+		},
+		Count:          helper.Int64ToPtr(int64(originalCount + 1)),
+		Message:        "scotty, we need more power",
+		PolicyOverride: false,
+		WriteRequest: structs.WriteRequest{
+			Region:    "global",
+			Namespace: job.Namespace,
+		},
+	}
+	var resp structs.JobRegisterResponse
+	err = msgpackrpc.CallWithCodec(codec, "Job.Scale", scale, &resp)
+	requireAssertion.NoError(err)
+	requireAssertion.NotEmpty(resp.EvalID)
+	requireAssertion.Greater(resp.EvalCreateIndex, resp.JobModifyIndex)
+
+	// Check the evaluation priority matches the job priority.
+	eval, err := fsmState.EvalByID(nil, resp.EvalID)
+	requireAssertion.Nil(err)
+	requireAssertion.NotNil(eval)
+	requireAssertion.EqualValues(resp.EvalCreateIndex, eval.CreateIndex)
+	requireAssertion.Equal(job.Priority, eval.Priority)
+	requireAssertion.Equal(job.Type, eval.Type)
+	requireAssertion.Equal(structs.EvalTriggerScaling, eval.TriggeredBy)
+	requireAssertion.Equal(job.ID, eval.JobID)
+	requireAssertion.Equal(structs.EvalStatusPending, eval.Status)
+	requireAssertion.NotZero(eval.CreateTime)
+	requireAssertion.NotZero(eval.ModifyTime)
+}
+
 func TestJobEndpoint_InvalidCount(t *testing.T) {
 	t.Parallel()
 	require := require.New(t)