Don't emit scaling event error when a deployment is underway (#11556)

.changelog/11556.txt

+```release-note:improvement
+scaling: Don't emit scaling action with error in case of active deployment
+```

nomad/job_endpoint.go

@@ -1103,31 +1103,7 @@ func (j *Job) Scale(args *structs.JobScaleRequest, reply *structs.JobRegisterRes
 		}
 
 		if deployment != nil && deployment.Active() && deployment.JobCreateIndex == job.CreateIndex {
-			msg := "job scaling blocked due to active deployment"
-			_, _, err := j.srv.raftApply(
-				structs.ScalingEventRegisterRequestType,
-				&structs.ScalingEventRequest{
-					Namespace: job.Namespace,
-					JobID:     job.ID,
-					TaskGroup: groupName,
-					ScalingEvent: &structs.ScalingEvent{
-						Time:          now,
-						PreviousCount: prevCount,
-						Message:       msg,
-						Error:         true,
-						Meta: map[string]interface{}{
-							"OriginalMessage": args.Message,
-							"OriginalCount":   *args.Count,
-							"OriginalMeta":    args.Meta,
-						},
-					},
-				},
-			)
-			if err != nil {
-				// just log the error, this was a best-effort attempt
-				j.logger.Error("scaling event create failed during block scaling action", "error", err)
-			}
-			return structs.NewErrRPCCoded(400, msg)
+			return structs.NewErrRPCCoded(400, "job scaling blocked due to active deployment")
 		}
 
 		// Commit the job update

nomad/job_endpoint_test.go

@@ -6769,22 +6769,6 @@ func TestJobEndpoint_Scale_DeploymentBlocking(t *testing.T) {
 			require.NotEmpty(resp.EvalID)
 			require.Greater(resp.EvalCreateIndex, resp.JobModifyIndex)
 		}
-
-		events, _, _ := state.ScalingEventsByJob(nil, job.Namespace, job.ID)
-		require.Equal(1, len(events[groupName]))
-		latestEvent := events[groupName][0]
-		if dLatest.Active() {
-			require.True(latestEvent.Error)
-			require.Nil(latestEvent.Count)
-			require.Contains(latestEvent.Message, "blocked due to active deployment")
-			require.Equal(latestEvent.Meta["OriginalCount"], newCount)
-			require.Equal(latestEvent.Meta["OriginalMessage"], scalingMessage)
-			require.Equal(latestEvent.Meta["OriginalMeta"], scalingMetadata)
-		} else {
-			require.False(latestEvent.Error)
-			require.NotNil(latestEvent.Count)
-			require.Equal(newCount, *latestEvent.Count)
-		}
 	}
 }