asim: fix one-off formatting in rand testing

Previously, some one-off formatting introduced extra lines in the randomized
testing output. This commit fixes the issue and makes the formatting approach
more consistent and principled.

Author: wenyihu6

pkg/kv/kvserver/asim/gen/generator.go

@@ -103,11 +103,14 @@ type MultiLoad []BasicLoad
 var _ LoadGen = MultiLoad{}
 
 func (ml MultiLoad) String() string {
-	var str string
-	for _, load := range ml {
-		str += load.String()
+	var buf strings.Builder
+	for i, load := range ml {
+		_, _ = fmt.Fprintf(&buf, "%s", load.String())
+		if i != len(ml)-1 {
+			_, _ = fmt.Fprintf(&buf, "\n")
+		}
 	}
-	return str
+	return buf.String()
 }
 
 func (ml MultiLoad) Generate(seed int64, settings *config.SimulationSettings) []workload.Generator {
@@ -161,7 +164,7 @@ func (bl BasicLoad) String() string {
 	} else {
 		_, _ = fmt.Fprintf(&buf, "%d-%dB/op, ", bl.MinBlockSize, bl.MaxBlockSize)
 	}
-	fmt.Fprintf(&buf, "%gops/s]\n", bl.Rate)
+	fmt.Fprintf(&buf, "%gops/s]", bl.Rate)
 	return buf.String()
 }
 
@@ -420,11 +423,14 @@ type MultiRanges []BasicRanges
 var _ RangeGen = MultiRanges{}
 
 func (mr MultiRanges) String() string {
-	var str string
-	for _, ranges := range mr {
-		str += fmt.Sprintf("%s\n", ranges.String())
+	var buf strings.Builder
+	for i, ranges := range mr {
+		_, _ = fmt.Fprintf(&buf, "%s", ranges.String())
+		if i != len(mr)-1 {
+			_, _ = fmt.Fprintf(&buf, "\n")
+		}
 	}
-	return str
+	return buf.String()
 }
 
 func (mr MultiRanges) Generate(
@@ -439,8 +445,11 @@ func (mr MultiRanges) Generate(
 	}
 	state.LoadRangeInfo(s, rangeInfos...)
 	var buf strings.Builder
-	for _, str := range rangeInfoStrings {
-		_, _ = fmt.Fprintf(&buf, "%s\n", str)
+	for i, str := range rangeInfoStrings {
+		_, _ = fmt.Fprintf(&buf, "%s", str)
+		if i != len(rangeInfoStrings)-1 {
+			_, _ = fmt.Fprintf(&buf, "\n")
+		}
 	}
 	return s, buf.String()
 }

pkg/kv/kvserver/asim/gen/printer.go

@@ -19,12 +19,11 @@ import (
 // Returns an empty string if no changes are found.
 func compareSettingsToDefault(settings config.SimulationSettings) string {
 	defaultSettings := config.DefaultSimulationSettings()
-	var changes []string
-
 	// Use reflection to compare all fields
 	settingsVal := reflect.ValueOf(settings)
 	defaultVal := reflect.ValueOf(*defaultSettings)
 	settingsType := reflect.TypeOf(settings)
+	var buf strings.Builder
 
 	for i := 0; i < settingsVal.NumField(); i++ {
 		field := settingsType.Field(i)
@@ -39,18 +38,17 @@ func compareSettingsToDefault(settings config.SimulationSettings) string {
 		}
 
 		if !reflect.DeepEqual(settingsFieldVal.Interface(), defaultFieldVal.Interface()) {
-			changes = append(changes, fmt.Sprintf("\t%s: %v (default: %v)",
+			if buf.Len() != 0 {
+				_, _ = fmt.Fprintf(&buf, "\n")
+			}
+			_, _ = fmt.Fprintf(&buf, "\t%s: %v (default: %v)",
 				field.Name,
 				settingsFieldVal.Interface(),
-				defaultFieldVal.Interface()))
+				defaultFieldVal.Interface())
 		}
 	}
 
-	if len(changes) == 0 {
-		return ""
-	}
-
-	return strings.Join(changes, "\n")
+	return buf.String()
 }
 
 // generateClusterVisualization generates a visualization of the cluster state.
@@ -82,14 +80,21 @@ func generateClusterVisualization(
 	if buf == nil {
 		return
 	}
-	_, _ = fmt.Fprintf(buf, "Cluster Set Up\n")
-	_, _ = fmt.Fprintf(buf, "%v", s.NodesString())
-	_, _ = fmt.Fprintf(buf, "Key Space\n%s", rangeStateStr)
-	_, _ = fmt.Fprintf(buf, "Event\n%s", eventGen.String())
-	_, _ = fmt.Fprintf(buf, "Workload Set Up\n%s", loadGen.String())
-
-	// Only print settings section if there are changes from defaults.
-	if settingsChanges := compareSettingsToDefault(settings); settingsChanges != "" {
-		_, _ = fmt.Fprintf(buf, "Changed Settings\n%s\n", settingsChanges)
+	// Helper function to return "empty" if string is empty, otherwise return the string
+	emptyIfBlank := func(s string) string {
+		if s == "" {
+			return "\tempty"
+		}
+		return s
 	}
+	clusterSetUp := emptyIfBlank(s.NodesString())
+	rangeState := emptyIfBlank(rangeStateStr)
+	event := emptyIfBlank(eventGen.String())
+	workloadSetUp := emptyIfBlank(loadGen.String())
+	settingsChanges := emptyIfBlank(compareSettingsToDefault(settings))
+	_, _ = fmt.Fprintf(buf, "Cluster Set Up\n%s\n", clusterSetUp)
+	_, _ = fmt.Fprintf(buf, "Key Space\n%s\n", rangeState)
+	_, _ = fmt.Fprintf(buf, "Event\n%s\n", event)
+	_, _ = fmt.Fprintf(buf, "Workload Set Up\n%s\n", workloadSetUp)
+	_, _ = fmt.Fprintf(buf, "Changed Settings\n%s", settingsChanges)
 }

pkg/kv/kvserver/asim/scheduled/scheduled_event_executor.go

@@ -72,9 +72,12 @@ func (e *eventExecutor) PrintEventSummary() string {
 	mutationEvents, assertionEvents := 0, 0
 	var buf strings.Builder
 	sort.Sort(e.scheduledEvents)
-	for _, e := range e.scheduledEvents {
-		_, _ = fmt.Fprintf(&buf, "%v\n", e)
-		if e.IsMutationEvent() {
+	for i, event := range e.scheduledEvents {
+		_, _ = fmt.Fprintf(&buf, "%v", event)
+		if i != len(e.scheduledEvents)-1 {
+			_, _ = fmt.Fprintf(&buf, "\n")
+		}
+		if event.IsMutationEvent() {
 			mutationEvents++
 		} else {
 			assertionEvents++
@@ -102,12 +105,15 @@ func (e *eventExecutor) PrintEventsExecuted() string {
 		panic("unexpected")
 	}
 	if len(e.scheduledEvents) == 0 {
-		return fmt.Sprintln("no events were scheduled")
+		return "no events were scheduled"
 	} else {
 		buf := strings.Builder{}
 		buf.WriteString(fmt.Sprintf("%d events executed:\n", len(e.scheduledEvents)))
-		for _, event := range e.scheduledEvents {
-			buf.WriteString(fmt.Sprintln(event.String()))
+		for i, event := range e.scheduledEvents {
+			_, _ = fmt.Fprintf(&buf, "%v", event.String())
+			if i != len(e.scheduledEvents)-1 {
+				_, _ = fmt.Fprintf(&buf, "\n")
+			}
 		}
 		return buf.String()
 	}

pkg/kv/kvserver/asim/state/impl.go

@@ -1436,7 +1436,7 @@ func (s *state) NodesString() string {
 		return cmp.Compare(a.nodeID, b.nodeID)
 	})
 
-	for _, n := range nodes {
+	for nID, n := range nodes {
 		_, _ = fmt.Fprintf(&buf, "\tn%d(", n.nodeID)
 		for _, locality := range n.desc.Locality.Tiers {
 			_, _ = fmt.Fprintf(&buf, "%s,", locality.Value)
@@ -1458,7 +1458,10 @@ func (s *state) NodesString() string {
 				_, _ = fmt.Fprintf(&buf, ",")
 			}
 		}
-		_, _ = fmt.Fprintf(&buf, "}\n")
+		_, _ = fmt.Fprintf(&buf, "}")
+		if nID != len(nodes)-1 {
+			_, _ = fmt.Fprintf(&buf, "\n")
+		}
 	}
 	return buf.String()
 }

pkg/kv/kvserver/asim/tests/datadriven_simulation_test.go

@@ -584,13 +584,13 @@ func TestDataDriven(t *testing.T) {
 									sample+1, failString)
 							}
 						}
-						_, _ = fmt.Fprintf(&buf, "==========================\n")
+						_, _ = fmt.Fprint(&buf, "==========================\n")
 					})
 				}
 				writeStateStrToFile(t, filepath.Join(plotDir, fmt.Sprintf("%s_setup.txt", name)), stateStrForOnce, rewrite)
 				if full {
-					_, _ = fmt.Fprintf(&buf, stateStrForOnce)
-					_, _ = fmt.Fprintf(&buf, "==========================\n")
+					_, _ = fmt.Fprintf(&buf, "%v\n", stateStrForOnce)
+					_, _ = fmt.Fprint(&buf, "==========================\n")
 				}
 				return buf.String()
 			case "assertion":

pkg/kv/kvserver/asim/tests/output.go

@@ -149,21 +149,29 @@ func (tr testResultsReport) String() string {
 		buf.WriteString(fmt.Sprintf("sample%d: start running\n", nthSample))
 		if failed || tr.flags.Has(OutputConfigGen) {
 			buf.WriteString(fmt.Sprintf("configurations generated using seed %d\n", output.seed))
-			buf.WriteString(fmt.Sprintf("\t%v\n", output.clusterGen))
-			buf.WriteString(fmt.Sprintf("\t%v\n", output.rangeGen))
-			buf.WriteString(fmt.Sprintf("%v", output.loadGen))
-			buf.WriteString(fmt.Sprintf("\t%v\n", output.eventGen))
+			clusterGenStr, rangeGenStr, loadGenStr, eventGenStr :=
+				output.clusterGen.String(), output.rangeGen.String(), output.loadGen.String(), output.eventGen.String()
+			emptyIfBlank := func(s string) string {
+				if s == "" {
+					return "empty"
+				}
+				return s
+			}
+			buf.WriteString(fmt.Sprintf("\t%v\n", emptyIfBlank(clusterGenStr)))
+			buf.WriteString(fmt.Sprintf("\t%v\n", emptyIfBlank(rangeGenStr)))
+			buf.WriteString(fmt.Sprintf("%v\n", emptyIfBlank(loadGenStr)))
+			buf.WriteString(fmt.Sprintf("\t%v\n", emptyIfBlank(eventGenStr)))
 		}
 		if failed || tr.flags.Has(OutputInitialState) {
 			buf.WriteString(fmt.Sprintf("initial state at %s:\n", output.initialTime.Format("2006-01-02 15:04:05")))
-			buf.WriteString(fmt.Sprintf("%v\n", output.initialStateStr))
+			buf.WriteString(fmt.Sprintf("\t%v\n", output.initialStateStr))
 		}
 		if failed || tr.flags.Has(OutputTopology) {
 			topology := output.history.S.Topology()
 			buf.WriteString(fmt.Sprintf("topology:\n%s", topology.String()))
 		}
 		if failed || tr.flags.Has(OutputEvents) {
-			buf.WriteString(output.eventExecutor.PrintEventsExecuted())
+			buf.WriteString(fmt.Sprintf("%v\n", output.eventExecutor.PrintEventsExecuted()))
 		}
 		if failed {
 			buf.WriteString(fmt.Sprintf("sample%d: failed assertion\n%s\n", nthSample, output.reason))

pkg/kv/kvserver/asim/tests/testdata/generated/example_rebalancing/example_rebalancing_setup.txt

@@ -13,4 +13,4 @@ Event
 Workload Set Up
 	[1,10000): 95%r large-block [128-256B/op, 7000ops/s]
 Changed Settings
-	StateExchangeDelay: 20s (default: 500ms)
+	StateExchangeDelay: 20s (default: 500ms)

pkg/kv/kvserver/asim/tests/testdata/non_rand/mma_skewed_cpu_skewed_write.txt

@@ -65,12 +65,10 @@ Key Space
 	[1,10000): 36(rf=3), 256MiB, [{s1*,s2,s3}:36]
 	[10001,20000): 36(rf=3), 256MiB, [{s4*,s5,s6}:36]
 Event
-	set LBRebalancingMode to 4
+	set LBRebalancingMode to 3
 Workload Set Up
 	[1,10000): read-only high-cpu [500.00cpu-us/op, 1B/op, 1000ops/s]
 	[10001,20000): write-only large-block [0.00cpu-us/write(raft), 1000B/op, 20000ops/s]
 Changed Settings
-	ReplicateQueueEnabled: false (default: true)
-	LeaseQueueEnabled: false (default: true)
 	SplitQueueEnabled: false (default: true)
 ==========================