app/vmagent: add -remoteWrite.roundDigits command-line option for limiting the number of digits after the point for stored values

This commit also adds --vm-round-digits command-line option to vmctl tool.

app/vmagent/remotewrite/client.go

@@ -8,7 +8,6 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
-	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -22,7 +21,7 @@ import (
 )
 
 var (
-	rateLimit = flagutil.NewArray("remoteWrite.rateLimit", "Optional rate limit in bytes per second for data sent to -remoteWrite.url. "+
+	rateLimit = flagutil.NewArrayInt("remoteWrite.rateLimit", "Optional rate limit in bytes per second for data sent to -remoteWrite.url. "+
 		"By default the rate limit is disabled. It can be useful for limiting load on remote storage when big amounts of buffered data "+
 		"is sent after temporary unavailability of the remote storage")
 	sendTimeout = flagutil.NewArrayDuration("remoteWrite.sendTimeout", "Timeout for sending a single block of data to -remoteWrite.url")
@@ -120,15 +119,9 @@ func newClient(argIdx int, remoteWriteURL, sanitizedURL string, fq *persistentqu
 		},
 		stopCh: make(chan struct{}),
 	}
-	if bytesPerSec := rateLimit.GetOptionalArg(argIdx); bytesPerSec != "" {
-		limit, err := strconv.ParseInt(bytesPerSec, 10, 64)
-		if err != nil {
-			logger.Fatalf("cannot parse -remoteWrite.rateLimit=%q for -remoteWrite.url=%q: %s", bytesPerSec, sanitizedURL, err)
-		}
-		if limit > 0 {
-			logger.Infof("applying %d bytes per second rate limit for -remoteWrite.url=%q", limit, sanitizedURL)
-			c.rl.perSecondLimit = limit
-		}
+	if bytesPerSec := rateLimit.GetOptionalArgOrDefault(argIdx, 0); bytesPerSec > 0 {
+		logger.Infof("applying %d bytes per second rate limit for -remoteWrite.url=%q", bytesPerSec, sanitizedURL)
+		c.rl.perSecondLimit = int64(bytesPerSec)
 	}
 	c.rl.limitReached = metrics.GetOrCreateCounter(fmt.Sprintf(`vmagent_remote_write_rate_limit_reached_total{url=%q}`, c.sanitizedURL))
 

app/vmagent/remotewrite/pendingseries.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/decimal"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/flagutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/persistentqueue"
@@ -35,9 +36,11 @@ type pendingSeries struct {
 	periodicFlusherWG sync.WaitGroup
 }
 
-func newPendingSeries(pushBlock func(block []byte)) *pendingSeries {
+func newPendingSeries(pushBlock func(block []byte), significantFigures, roundDigits int) *pendingSeries {
 	var ps pendingSeries
 	ps.wr.pushBlock = pushBlock
+	ps.wr.significantFigures = significantFigures
+	ps.wr.roundDigits = roundDigits
 	ps.stopCh = make(chan struct{})
 	ps.periodicFlusherWG.Add(1)
 	go func() {
@@ -85,9 +88,17 @@ type writeRequest struct {
 	// Move lastFlushTime to the top of the struct in order to guarantee atomic access on 32-bit architectures.
 	lastFlushTime uint64
 
-	wr        prompbmarshal.WriteRequest
+	// pushBlock is called when whe write request is ready to be sent.
 	pushBlock func(block []byte)
 
+	// How many significant figures must be left before sending the writeRequest to pushBlock.
+	significantFigures int
+
+	// How many decimal digits after point must be left before sending the writeRequest to pushBlock.
+	roundDigits int
+
+	wr prompbmarshal.WriteRequest
+
 	tss []prompbmarshal.TimeSeries
 
 	labels  []prompbmarshal.Label
@@ -96,6 +107,8 @@ type writeRequest struct {
 }
 
 func (wr *writeRequest) reset() {
+	// Do not reset pushBlock, significantFigures and roundDigits, since they are re-used.
+
 	wr.wr.Timeseries = nil
 
 	for i := range wr.tss {
@@ -114,11 +127,28 @@ func (wr *writeRequest) reset() {
 
 func (wr *writeRequest) flush() {
 	wr.wr.Timeseries = wr.tss
+	wr.adjustSampleValues()
 	atomic.StoreUint64(&wr.lastFlushTime, fasttime.UnixTimestamp())
 	pushWriteRequest(&wr.wr, wr.pushBlock)
 	wr.reset()
 }
 
+func (wr *writeRequest) adjustSampleValues() {
+	samples := wr.samples
+	if n := wr.significantFigures; n > 0 {
+		for i := range samples {
+			s := &samples[i]
+			s.Value = decimal.RoundToSignificantFigures(s.Value, n)
+		}
+	}
+	if n := wr.roundDigits; n < 100 {
+		for i := range samples {
+			s := &samples[i]
+			s.Value = decimal.RoundToDecimalDigits(s.Value, n)
+		}
+	}
+}
+
 func (wr *writeRequest) push(src []prompbmarshal.TimeSeries) {
 	tssDst := wr.tss
 	for i := range src {

app/vmagent/remotewrite/remotewrite.go

@@ -7,7 +7,6 @@ import (
 	"sync/atomic"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/cgroup"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/decimal"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/flagutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/memory"
@@ -31,9 +30,13 @@ var (
 		"for each -remoteWrite.url. When buffer size reaches the configured maximum, then old data is dropped when adding new data to the buffer. "+
 		"Buffered data is stored in ~500MB chunks, so the minimum practical value for this flag is 500000000. "+
 		"Disk usage is unlimited if the value is set to 0")
-	significantFigures = flag.Int("remoteWrite.significantFigures", 0, "The number of significant figures to leave in metric values before writing them to remote storage. "+
-		"See https://en.wikipedia.org/wiki/Significant_figures . Zero value saves all the significant figures. "+
-		"This option may be used for increasing on-disk compression level for the stored metrics")
+	significantFigures = flagutil.NewArrayInt("remoteWrite.significantFigures", "The number of significant figures to leave in metric values before writing them "+
+		"to remote storage. See https://en.wikipedia.org/wiki/Significant_figures . Zero value saves all the significant figures. "+
+		"This option may be used for improving data compression for the stored metrics. See also -remoteWrite.roundDigits")
+	roundDigits = flagutil.NewArrayInt("remoteWrite.roundDigits", "Round metric values to this number of decimal digits after the point before writing them to remote storage. "+
+		"Examples: -remoteWrite.roundDigits=2 would round 1.236 to 1.24, while -remoteWrite.roundDigits=-1 would round 126.78 to 130. "+
+		"By default digits rounding is disabled. Set it to 100 for disabling it for a particular remote storage. "+
+		"This option may be used for improving data compression for the stored metrics")
 )
 
 var rwctxs []*remoteWriteCtx
@@ -137,17 +140,6 @@ func Stop() {
 //
 // Note that wr may be modified by Push due to relabeling and rounding.
 func Push(wr *prompbmarshal.WriteRequest) {
-	if *significantFigures > 0 {
-		// Round values according to significantFigures
-		for i := range wr.Timeseries {
-			samples := wr.Timeseries[i].Samples
-			for j := range samples {
-				s := &samples[j]
-				s.Value = decimal.Round(s.Value, *significantFigures)
-			}
-		}
-	}
-
 	var rctx *relabelCtx
 	rcs := allRelabelConfigs.Load().(*relabelConfigs)
 	prcsGlobal := rcs.global
@@ -213,9 +205,11 @@ func newRemoteWriteCtx(argIdx int, remoteWriteURL string, maxInmemoryBlocks int,
 		return float64(fq.GetInmemoryQueueLen())
 	})
 	c := newClient(argIdx, remoteWriteURL, sanitizedURL, fq, *queues)
+	sf := significantFigures.GetOptionalArgOrDefault(argIdx, 0)
+	rd := roundDigits.GetOptionalArgOrDefault(argIdx, 100)
 	pss := make([]*pendingSeries, *queues)
 	for i := range pss {
-		pss[i] = newPendingSeries(fq.MustWriteBlock)
+		pss[i] = newPendingSeries(fq.MustWriteBlock, sf, rd)
 	}
 	return &remoteWriteCtx{
 		idx: argIdx,

app/vmctl/README.md

@@ -413,15 +413,20 @@ Moreover, such values may be just a result of [floating point arithmetic](https:
 create a [false precision](https://en.wikipedia.org/wiki/False_precision) and result into bad compression ratio 
 according to [information theory](https://en.wikipedia.org/wiki/Information_theory). 
 
-The `--vm-significant-figures` flag allows to limit the number of significant figures. It takes no effect if set 
-to 0 (by default), but set `--vm-significant-figures=5` and `102.342305` will be rounded to `102.34`. Such value will 
-have much higher compression ratio comparing to previous one and will save some extra disk space after the migration. 
-The most common case for using this flag is to reduce number of significant figures for time series storing aggregation 
-results such as `average`, `rate`, etc.   
+`vmctl` provides the following flags for improving data compression:
+
+* `--vm-round-digits` flag for rounding processed values to the given number of decimal digits after the point.
+  For example, `--vm-round-digits=2` would round `1.2345` to `1.23`. By default the rounding is disabled.
+
+* `--vm-significant-figures` flag for limiting the number of significant figures in processed values. It takes no effect if set
+  to 0 (by default), but set `--vm-significant-figures=5` and `102.342305` will be rounded to `102.34`.
+
+The most common case for using these flags is to improve data compression for time series storing aggregation
+results such as `average`, `rate`, etc.
 
 ### Adding extra labels
 
  `vmctl` allows to add extra labels to all imported series. It can be achived with flag `--vm-extra-label label=value`. 
  If multiple labels needs to be added, set flag for each label, for example, `--vm-extra-label label1=value1 --vm-extra-label label2=value2`.
  If timeseries already have label, that must be added with `--vm-extra-label` flag, flag has priority and will override label value from timeseries.
- 
+ 

app/vmctl/flags.go

@@ -29,6 +29,7 @@ const (
 	vmCompress           = "vm-compress"
 	vmBatchSize          = "vm-batch-size"
 	vmSignificantFigures = "vm-significant-figures"
+	vmRoundDigits        = "vm-round-digits"
 	vmExtraLabel         = "vm-extra-label"
 )
 
@@ -77,6 +78,13 @@ var (
 			Value: 0,
 			Usage: "The number of significant figures to leave in metric values before importing. " +
 				"See https://en.wikipedia.org/wiki/Significant_figures. Zero value saves all the significant figures. " +
+				"This option may be used for increasing on-disk compression level for the stored metrics. " +
+				"See also --vm-round-digits option",
+		},
+		&cli.IntFlag{
+			Name:  vmRoundDigits,
+			Value: 100,
+			Usage: "Round metric values to the given number of decimal digits after the point. " +
 				"This option may be used for increasing on-disk compression level for the stored metrics",
 		},
 		&cli.StringSliceFlag{

app/vmctl/main.go

@@ -153,6 +153,7 @@ func initConfigVM(c *cli.Context) vm.Config {
 		AccountID:          c.String(vmAccountID),
 		BatchSize:          c.Int(vmBatchSize),
 		SignificantFigures: c.Int(vmSignificantFigures),
+		RoundDigits:        c.Int(vmRoundDigits),
 		ExtraLabels:        c.StringSlice(vmExtraLabel),
 	}
 }

app/vmctl/vm/vm.go

@@ -42,6 +42,9 @@ type Config struct {
 	// in metric values before importing.
 	// Zero value saves all the significant decimal places
 	SignificantFigures int
+	// RoundDigits defines the number of decimal digits after the point that must be left
+	// in metric values before importing.
+	RoundDigits int
 	// ExtraLabels that will be added to all imported series. Must be in label=value format.
 	ExtraLabels []string
 }
@@ -136,7 +139,7 @@ func NewImporter(cfg Config) (*Importer, error) {
 	for i := 0; i < int(cfg.Concurrency); i++ {
 		go func() {
 			defer im.wg.Done()
-			im.startWorker(cfg.BatchSize, cfg.SignificantFigures)
+			im.startWorker(cfg.BatchSize, cfg.SignificantFigures, cfg.RoundDigits)
 		}()
 	}
 	im.ResetStats()
@@ -170,7 +173,7 @@ func (im *Importer) Close() {
 	})
 }
 
-func (im *Importer) startWorker(batchSize, significantFigures int) {
+func (im *Importer) startWorker(batchSize, significantFigures, roundDigits int) {
 	var batch []*TimeSeries
 	var dataPoints int
 	var waitForBatch time.Time
@@ -192,9 +195,13 @@ func (im *Importer) startWorker(batchSize, significantFigures int) {
 			}
 
 			if significantFigures > 0 {
-				// Round values according to significantFigures
 				for i, v := range ts.Values {
-					ts.Values[i] = decimal.Round(v, significantFigures)
+					ts.Values[i] = decimal.RoundToSignificantFigures(v, significantFigures)
+				}
+			}
+			if roundDigits < 100 {
+				for i, v := range ts.Values {
+					ts.Values[i] = decimal.RoundToDecimalDigits(v, roundDigits)
 				}
 			}
 

docs/CHANGELOG.md

@@ -6,6 +6,7 @@
 * FEATURE: added `-loggerTimezone` command-line flag for adjusting time zone for timestamps in log messages. By default UTC is used.
 * FEATURE: added `-search.maxStepForPointsAdjustment` command-line flag, which can be used for disabling adjustment for points returned by `/api/v1/query_range` handler if such points have timestamps closer than `-search.latencyOffset` to the current time. Such points may contain incomplete data, so they are substituted by the previous values for `step` query args smaller than one minute by default.
 * FEATURE: vmalert: added `-datasource.queryStep` command-line flag for passing optional `step` query arg to `/api/v1/query` endpoint. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1025
+* FEATURE: vmagent: added `-remoteWrite.roundDigits` command-line option for rounding metric values to the given number of decimal digits after the point before sending the metric to the corresponding `-remoteWrite.url`. This option can be used for improving data compression on the remote storage, because values with lower number of decimal digits can be compressed better than values with bigger number of decimal digits.
 * FEATURE: vmagent: added `-remoteWrite.rateLimit` command-line flag for limiting data transfer rate to `-remoteWrite.url`. This may be useful when big amounts of buffered data is sent after temporarily unavailability of the remote storage. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1035
 * FEATURE: vmagent: export `vm_promscrape_scrapes_failed_per_url_total` and `vm_promscrape_scrapes_skipped_by_sample_limit_per_url_total` counters, which may help identifying improperly working scrape targets.
 

docs/vmctl.md

@@ -413,15 +413,20 @@ Moreover, such values may be just a result of [floating point arithmetic](https:
 create a [false precision](https://en.wikipedia.org/wiki/False_precision) and result into bad compression ratio 
 according to [information theory](https://en.wikipedia.org/wiki/Information_theory). 
 
-The `--vm-significant-figures` flag allows to limit the number of significant figures. It takes no effect if set 
-to 0 (by default), but set `--vm-significant-figures=5` and `102.342305` will be rounded to `102.34`. Such value will 
-have much higher compression ratio comparing to previous one and will save some extra disk space after the migration. 
-The most common case for using this flag is to reduce number of significant figures for time series storing aggregation 
-results such as `average`, `rate`, etc.   
+`vmctl` provides the following flags for improving data compression:
+
+* `--vm-round-digits` flag for rounding processed values to the given number of decimal digits after the point.
+  For example, `--vm-round-digits=2` would round `1.2345` to `1.23`. By default the rounding is disabled.
+
+* `--vm-significant-figures` flag for limiting the number of significant figures in processed values. It takes no effect if set
+  to 0 (by default), but set `--vm-significant-figures=5` and `102.342305` will be rounded to `102.34`.
+
+The most common case for using these flags is to improve data compression for time series storing aggregation
+results such as `average`, `rate`, etc.
 
 ### Adding extra labels
 
  `vmctl` allows to add extra labels to all imported series. It can be achived with flag `--vm-extra-label label=value`. 
  If multiple labels needs to be added, set flag for each label, for example, `--vm-extra-label label1=value1 --vm-extra-label label2=value2`.
  If timeseries already have label, that must be added with `--vm-extra-label` flag, flag has priority and will override label value from timeseries.
- 
+ 

lib/decimal/decimal.go

@@ -298,8 +298,21 @@ func maxUpExponent(v int64) int16 {
 	}
 }
 
-// Round f to value with the given number of significant figures.
-func Round(f float64, digits int) float64 {
+// RoundToDecimalDigits rounds f to the given number of decimal digits after the point.
+//
+// See also RoundToSignificantFigures.
+func RoundToDecimalDigits(f float64, digits int) float64 {
+	if digits <= -100 || digits >= 100 {
+		return f
+	}
+	m := math.Pow10(digits)
+	return math.Round(f*m) / m
+}
+
+// RoundToSignificantFigures rounds f to value with the given number of significant figures.
+//
+// See also RoundToDecimalDigits.
+func RoundToSignificantFigures(f float64, digits int) float64 {
 	if digits <= 0 || digits >= 18 {
 		return f
 	}

lib/decimal/decimal_test.go

@@ -7,10 +7,34 @@ import (
 	"testing"
 )
 
-func TestRoundInplace(t *testing.T) {
+func TestRoundToDecimalDigits(t *testing.T) {
 	f := func(f float64, digits int, resultExpected float64) {
 		t.Helper()
-		result := Round(f, digits)
+		result := RoundToDecimalDigits(f, digits)
+		if math.IsNaN(result) {
+			if !math.IsNaN(resultExpected) {
+				t.Fatalf("unexpected result; got %v; want %v", result, resultExpected)
+			}
+		}
+		if result != resultExpected {
+			t.Fatalf("unexpected result; got %v; want %v", result, resultExpected)
+		}
+	}
+	f(12.34, 0, 12)
+	f(12.57, 0, 13)
+	f(-1.578, 2, -1.58)
+	f(-1.578, 3, -1.578)
+	f(1234, -2, 1200)
+	f(1235, -1, 1240)
+	f(1234, 0, 1234)
+	f(1234.6, 0, 1235)
+	f(123.4e-99, 99, 123e-99)
+}
+
+func TestRoundToSignificantFigures(t *testing.T) {
+	f := func(f float64, digits int, resultExpected float64) {
+		t.Helper()
+		result := RoundToSignificantFigures(f, digits)
 		if math.IsNaN(result) {
 			if !math.IsNaN(resultExpected) {
 				t.Fatalf("unexpected result; got %v; want %v", result, resultExpected)

lib/flagutil/array.go

@@ -35,6 +35,15 @@ func NewArrayBool(name, description string) *ArrayBool {
 	return &a
 }
 
+// NewArrayInt returns new ArrayInt with the given name and description.
+func NewArrayInt(name string, description string) *ArrayInt {
+	description += "\nSupports `array` of values separated by comma" +
+		" or specified via multiple flags."
+	var a ArrayInt
+	flag.Var(&a, name, description)
+	return &a
+}
+
 // Array is a flag that holds an array of values.
 //
 // It may be set either by specifying multiple flags with the given name
@@ -223,3 +232,41 @@ func (a *ArrayDuration) GetOptionalArgOrDefault(argIdx int, defaultValue time.Du
 	}
 	return x[argIdx]
 }
+
+// ArrayInt is flag that holds an array of ints.
+type ArrayInt []int
+
+// String implements flag.Value interface
+func (a *ArrayInt) String() string {
+	x := *a
+	formattedInts := make([]string, len(x))
+	for i, v := range x {
+		formattedInts[i] = strconv.Itoa(v)
+	}
+	return strings.Join(formattedInts, ",")
+}
+
+// Set implements flag.Value interface
+func (a *ArrayInt) Set(value string) error {
+	values := parseArrayValues(value)
+	for _, v := range values {
+		n, err := strconv.Atoi(v)
+		if err != nil {
+			return err
+		}
+		*a = append(*a, n)
+	}
+	return nil
+}
+
+// GetOptionalArg returns optional arg under the given argIdx.
+func (a *ArrayInt) GetOptionalArgOrDefault(argIdx int, defaultValue int) int {
+	x := *a
+	if argIdx < len(x) {
+		return x[argIdx]
+	}
+	if len(x) == 1 {
+		return x[0]
+	}
+	return defaultValue
+}

lib/flagutil/array_test.go

@@ -12,14 +12,18 @@ var (
 	fooFlag         Array
 	fooFlagDuration ArrayDuration
 	fooFlagBool     ArrayBool
+	fooFlagInt      ArrayInt
 )
 
 func init() {
-	os.Args = append(os.Args, "--fooFlag=foo", "--fooFlag=bar", "--fooFlagDuration=10s", "--fooFlagDuration=5m")
+	os.Args = append(os.Args, "--fooFlag=foo", "--fooFlag=bar")
+	os.Args = append(os.Args, "--fooFlagDuration=10s", "--fooFlagDuration=5m")
 	os.Args = append(os.Args, "--fooFlagBool=true", "--fooFlagBool=false,true", "--fooFlagBool")
+	os.Args = append(os.Args, "--fooFlagInt=1", "--fooFlagInt=2,3")
 	flag.Var(&fooFlag, "fooFlag", "test")
 	flag.Var(&fooFlagDuration, "fooFlagDuration", "test")
 	flag.Var(&fooFlagBool, "fooFlagBool", "test")
+	flag.Var(&fooFlagInt, "fooFlagInt", "test")
 }
 
 func TestMain(m *testing.M) {
@@ -28,16 +32,16 @@ func TestMain(m *testing.M) {
 }
 
 func TestArray(t *testing.T) {
-	expected := map[string]struct{}{
-		"foo": {},
-		"bar": {},
+	expected := []string{
+		"foo",
+		"bar",
 	}
 	if len(expected) != len(fooFlag) {
 		t.Errorf("len array flag (%d) is not equal to %d", len(fooFlag), len(expected))
 	}
-	for _, i := range fooFlag {
-		if _, ok := expected[i]; !ok {
-			t.Errorf("unexpected item in array %v", i)
+	for i, v := range fooFlag {
+		if v != expected[i] {
+			t.Errorf("unexpected item in array %q", v)
 		}
 	}
 }
@@ -101,16 +105,16 @@ func TestArrayString(t *testing.T) {
 }
 
 func TestArrayDuration(t *testing.T) {
-	expected := map[time.Duration]struct{}{
-		time.Second * 10: {},
-		time.Minute * 5:  {},
+	expected := []time.Duration{
+		time.Second * 10,
+		time.Minute * 5,
 	}
 	if len(expected) != len(fooFlagDuration) {
 		t.Errorf("len array flag (%d) is not equal to %d", len(fooFlag), len(expected))
 	}
-	for _, i := range fooFlagDuration {
-		if _, ok := expected[i]; !ok {
-			t.Errorf("unexpected item in array %v", i)
+	for i, v := range fooFlagDuration {
+		if v != expected[i] {
+			t.Errorf("unexpected item in array %s", v)
 		}
 	}
 }
@@ -130,7 +134,7 @@ func TestArrayDurationSet(t *testing.T) {
 }
 
 func TestArrayDurationGetOptionalArg(t *testing.T) {
-	f := func(s string, argIdx int, expectedValue time.Duration, defaultValue time.Duration) {
+	f := func(s string, argIdx int, expectedValue, defaultValue time.Duration) {
 		t.Helper()
 		var a ArrayDuration
 		_ = a.Set(s)
@@ -219,3 +223,60 @@ func TestArrayBoolString(t *testing.T) {
 	f("true,false")
 	f("false,true")
 }
+
+func TestArrayInt(t *testing.T) {
+	expected := []int{1, 2, 3}
+	if len(expected) != len(fooFlagInt) {
+		t.Errorf("len array flag (%d) is not equal to %d", len(fooFlag), len(expected))
+	}
+	for i, n := range fooFlagInt {
+		if n != expected[i] {
+			t.Errorf("unexpected item in array %d", n)
+		}
+	}
+}
+
+func TestArrayIntSet(t *testing.T) {
+	f := func(s string, expectedValues []int) {
+		t.Helper()
+		var a ArrayInt
+		_ = a.Set(s)
+		if !reflect.DeepEqual([]int(a), expectedValues) {
+			t.Fatalf("unexpected values parsed;\ngot\n%q\nwant\n%q", a, expectedValues)
+		}
+	}
+	f("", nil)
+	f(`1`, []int{1})
+	f(`-2,3,-64`, []int{-2, 3, -64})
+}
+
+func TestArrayIntGetOptionalArg(t *testing.T) {
+	f := func(s string, argIdx int, expectedValue, defaultValue int) {
+		t.Helper()
+		var a ArrayInt
+		_ = a.Set(s)
+		v := a.GetOptionalArgOrDefault(argIdx, defaultValue)
+		if v != expectedValue {
+			t.Fatalf("unexpected value; got %d; want %d", v, expectedValue)
+		}
+	}
+	f("", 0, 123, 123)
+	f("", 1, -34, -34)
+	f("10,1", 1, 1, 234)
+	f("10", 3, 10, -34)
+}
+
+func TestArrayIntString(t *testing.T) {
+	f := func(s string) {
+		t.Helper()
+		var a ArrayInt
+		_ = a.Set(s)
+		result := a.String()
+		if result != s {
+			t.Fatalf("unexpected string;\ngot\n%s\nwant\n%s", result, s)
+		}
+	}
+	f("")
+	f("10,1")
+	f("-5,1,123")
+}