apptest: add tests for stale nans in instant query (#7621)

### Describe Your Changes

These are the integration tests that confirm that instant queries may
return stale NaNs when the query contains a rollup function.

The bug was reported at #5806. There is also a fix: #7275. The tests in
this PR will be used co confirm that the fix works.

Some test refactoring has been done along the way. Sorry, couldn't
resist.

### Checklist

The following checks are **mandatory**:

- [x] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).

---------

Signed-off-by: Artem Fetishev <rtm@victoriametrics.com>

apptest/client.go

@@ -1,6 +1,7 @@
 package apptest
 
 import (
+	"bytes"
 	"io"
 	"net/http"
 	"net/url"
@@ -36,13 +37,13 @@ func (c *Client) CloseConnections() {
 // the response body to the caller.
 func (c *Client) Get(t *testing.T, url string, wantStatusCode int) string {
 	t.Helper()
-	return c.do(t, http.MethodGet, url, "", "", wantStatusCode)
+	return c.do(t, http.MethodGet, url, "", nil, wantStatusCode)
 }
 
 // Post sends a HTTP POST request. Once the function receives a response, it
 // checks whether the response status code matches the expected one and returns
 // the response body to the caller.
-func (c *Client) Post(t *testing.T, url, contentType, data string, wantStatusCode int) string {
+func (c *Client) Post(t *testing.T, url, contentType string, data []byte, wantStatusCode int) string {
 	t.Helper()
 	return c.do(t, http.MethodPost, url, contentType, data, wantStatusCode)
 }
@@ -52,16 +53,16 @@ func (c *Client) Post(t *testing.T, url, contentType, data string, wantStatusCod
 // matches the expected one and returns the response body to the caller.
 func (c *Client) PostForm(t *testing.T, url string, data url.Values, wantStatusCode int) string {
 	t.Helper()
-	return c.Post(t, url, "application/x-www-form-urlencoded", data.Encode(), wantStatusCode)
+	return c.Post(t, url, "application/x-www-form-urlencoded", []byte(data.Encode()), wantStatusCode)
 }
 
 // do prepares a HTTP request, sends it to the server, receives the response
 // from the server, ensures then response code matches the expected one, reads
 // the rentire response body and returns it to the caller.
-func (c *Client) do(t *testing.T, method, url, contentType, data string, wantStatusCode int) string {
+func (c *Client) do(t *testing.T, method, url, contentType string, data []byte, wantStatusCode int) string {
 	t.Helper()
 
-	req, err := http.NewRequest(method, url, strings.NewReader(data))
+	req, err := http.NewRequest(method, url, bytes.NewReader(data))
 	if err != nil {
 		t.Fatalf("could not create a HTTP request: %v", err)
 	}

apptest/model.go

@@ -8,10 +8,13 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	pb "github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
 )
 
 // PrometheusQuerier contains methods available to Prometheus-like HTTP API for Querying
 type PrometheusQuerier interface {
+	PrometheusAPIV1Export(t *testing.T, query, start, end string, opts QueryOpts) *PrometheusAPIV1QueryResponse
 	PrometheusAPIV1Query(t *testing.T, query, time, step string, opts QueryOpts) *PrometheusAPIV1QueryResponse
 	PrometheusAPIV1QueryRange(t *testing.T, query, start, end, step string, opts QueryOpts) *PrometheusAPIV1QueryResponse
 	PrometheusAPIV1Series(t *testing.T, matchQuery string, opts QueryOpts) *PrometheusAPIV1SeriesResponse
@@ -19,6 +22,7 @@ type PrometheusQuerier interface {
 
 // PrometheusWriter contains methods available to Prometheus-like HTTP API for Writing new data
 type PrometheusWriter interface {
+	PrometheusAPIV1Write(t *testing.T, records []pb.TimeSeries, opts QueryOpts)
 	PrometheusAPIV1ImportPrometheus(t *testing.T, records []string, opts QueryOpts)
 }
 

apptest/testcase.go

@@ -54,6 +54,17 @@ func (tc *TestCase) Stop() {
 	}
 }
 
+// MustStartDefaultVmsingle is a test helper function that starts an instance of
+// vmsingle with defaults suitable for most tests.
+func (tc *TestCase) MustStartDefaultVmsingle() *Vmsingle {
+	tc.t.Helper()
+
+	return tc.MustStartVmsingle("vmsingle", []string{
+		"-storageDataPath=" + tc.Dir() + "/vmsingle",
+		"-retentionPeriod=100y",
+	})
+}
+
 // MustStartVmsingle is a test helper function that starts an instance of
 // vmsingle and fails the test if the app fails to start.
 func (tc *TestCase) MustStartVmsingle(instance string, flags []string) *Vmsingle {
@@ -118,7 +129,8 @@ func (c *vmcluster) ForceFlush(t *testing.T) {
 	}
 }
 
-// MustStartCluster is a typical cluster configuration.
+// MustStartDefaultCluster is a typical cluster configuration suitable for most
+// tests.
 //
 // The cluster consists of two vmstorages, one vminsert and one vmselect, no
 // data replication.
@@ -128,7 +140,7 @@ func (c *vmcluster) ForceFlush(t *testing.T) {
 // vmselect) but instead just need a typical cluster configuration to verify
 // some business logic (such as API surface, or MetricsQL). Such cluster
 // tests usually come paired with corresponding vmsingle tests.
-func (tc *TestCase) MustStartCluster() PrometheusWriteQuerier {
+func (tc *TestCase) MustStartDefaultCluster() PrometheusWriteQuerier {
 	tc.t.Helper()
 
 	vmstorage1 := tc.MustStartVmstorage("vmstorage-1", []string{

apptest/tests/key_concepts_test.go

@@ -33,10 +33,7 @@ func TestSingleKeyConceptsQuery(t *testing.T) {
 	tc := apptest.NewTestCase(t)
 	defer tc.Stop()
 
-	sut := tc.MustStartVmsingle("vmsingle", []string{
+	sut := tc.MustStartDefaultVmsingle()
-		"-storageDataPath=" + tc.Dir() + "/vmstorage",
-		"-retentionPeriod=100y",
-	})
 
 	testKeyConceptsQueryData(t, sut)
 }
@@ -47,7 +44,7 @@ func TestClusterKeyConceptsQueryData(t *testing.T) {
 	tc := apptest.NewTestCase(t)
 	defer tc.Stop()
 
-	sut := tc.MustStartCluster()
+	sut := tc.MustStartDefaultCluster()
 
 	testKeyConceptsQueryData(t, sut)
 }

apptest/tests/metricsql_test.go

@@ -0,0 +1,119 @@
+package tests
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/apptest"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/decimal"
+	pb "github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
+)
+
+func millis(s string) int64 {
+	t, err := time.Parse(time.RFC3339, s)
+	if err != nil {
+		panic(fmt.Sprintf("could not parse time %q: %v", s, err))
+	}
+	return t.UnixMilli()
+}
+
+var staleNaNsData = func() []pb.TimeSeries {
+	return []pb.TimeSeries{
+		{
+			Labels: []pb.Label{
+				{
+					Name:  "__name__",
+					Value: "metric",
+				},
+			},
+			Samples: []pb.Sample{
+				{
+					Value:     1,
+					Timestamp: millis("2024-01-01T00:01:00Z"),
+				},
+				{
+					Value:     decimal.StaleNaN,
+					Timestamp: millis("2024-01-01T00:02:00Z"),
+				},
+			},
+		},
+	}
+}()
+
+func TestSingleInstantQueryDoesNotReturnStaleNaNs(t *testing.T) {
+	tc := apptest.NewTestCase(t)
+	defer tc.Stop()
+
+	sut := tc.MustStartDefaultVmsingle()
+
+	testInstantQueryDoesNotReturnStaleNaNs(t, sut)
+}
+
+func TestClusterInstantQueryDoesNotReturnStaleNaNs(t *testing.T) {
+	tc := apptest.NewTestCase(t)
+	defer tc.Stop()
+
+	sut := tc.MustStartDefaultCluster()
+
+	testInstantQueryDoesNotReturnStaleNaNs(t, sut)
+}
+
+func testInstantQueryDoesNotReturnStaleNaNs(t *testing.T, sut apptest.PrometheusWriteQuerier) {
+	opts := apptest.QueryOpts{Timeout: "5s", Tenant: "0"}
+
+	sut.PrometheusAPIV1Write(t, staleNaNsData, opts)
+	sut.ForceFlush(t)
+
+	var got, want *apptest.PrometheusAPIV1QueryResponse
+	cmpOptions := []cmp.Option{
+		cmpopts.IgnoreFields(apptest.PrometheusAPIV1QueryResponse{}, "Status", "Data.ResultType"),
+		cmpopts.EquateNaNs(),
+	}
+
+	// Verify that instant query returns the first point.
+
+	got = sut.PrometheusAPIV1Query(t, "metric", "2024-01-01T00:01:00.000Z", "5m", opts)
+	want = apptest.NewPrometheusAPIV1QueryResponse(t, `{"data": {"result": [{"metric": {"__name__": "metric"}}]}}`)
+	want.Data.Result[0].Sample = apptest.NewSample(t, "2024-01-01T00:01:00Z", 1)
+	if diff := cmp.Diff(want, got, cmpOptions...); diff != "" {
+		t.Errorf("unexpected response (-want, +got):\n%s", diff)
+	}
+
+	// Verify that instant query does not return stale NaN.
+
+	got = sut.PrometheusAPIV1Query(t, "metric", "2024-01-01T00:02:00.000Z", "5m", opts)
+	want = apptest.NewPrometheusAPIV1QueryResponse(t, `{"data": {"result": []}}`)
+	// Empty response, stale NaN is not included into response
+	if diff := cmp.Diff(want, got, cmpOptions...); diff != "" {
+		t.Errorf("unexpected response (-want, +got):\n%s", diff)
+	}
+
+	// Verify that instant query with default rollup function returns stale NaN
+	// while it must not.
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5806
+
+	got = sut.PrometheusAPIV1Query(t, "metric[2m]", "2024-01-01T00:02:00.000Z", "5m", opts)
+	want = apptest.NewPrometheusAPIV1QueryResponse(t, `{"data": {"result": [{"metric": {"__name__": "metric"}, "values": []}]}}`)
+	s := make([]*apptest.Sample, 2)
+	s[0] = apptest.NewSample(t, "2024-01-01T00:01:00Z", 1)
+	s[1] = apptest.NewSample(t, "2024-01-01T00:02:00Z", decimal.StaleNaN)
+	want.Data.Result[0].Samples = s
+	if diff := cmp.Diff(want, got, cmpOptions...); diff != "" {
+		t.Errorf("unexpected response (-want, +got):\n%s", diff)
+	}
+
+	// Verify that exported data contains stale NaN.
+
+	got = sut.PrometheusAPIV1Export(t, `{__name__="metric"}`, "2024-01-01T00:01:00.000Z", "2024-01-01T00:02:00.000Z", opts)
+	want = apptest.NewPrometheusAPIV1QueryResponse(t, `{"data": {"result": [{"metric": {"__name__": "metric"}, "values": []}]}}`)
+	s = make([]*apptest.Sample, 2)
+	s[0] = apptest.NewSample(t, "2024-01-01T00:01:00Z", 1)
+	s[1] = apptest.NewSample(t, "2024-01-01T00:02:00Z", decimal.StaleNaN)
+	want.Data.Result[0].Samples = s
+	if diff := cmp.Diff(want, got, cmpOptions...); diff != "" {
+		t.Errorf("unexpected response (-want, +got):\n%s", diff)
+	}
+}

apptest/vminsert.go

@@ -7,6 +7,9 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	pb "github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
+	"github.com/golang/snappy"
 )
 
 // Vminsert holds the state of a vminsert app and provides vminsert-specific
@@ -46,6 +49,20 @@ func StartVminsert(instance string, flags []string, cli *Client) (*Vminsert, err
 	}, nil
 }
 
+// PrometheusAPIV1Write is a test helper function that inserts a
+// collection of records in Prometheus remote-write format by sending a HTTP
+// POST request to /prometheus/api/v1/write vminsert endpoint.
+func (app *Vminsert) PrometheusAPIV1Write(t *testing.T, records []pb.TimeSeries, opts QueryOpts) {
+	t.Helper()
+
+	url := fmt.Sprintf("http://%s/insert/%s/prometheus/api/v1/write", app.httpListenAddr, opts.Tenant)
+	wr := pb.WriteRequest{Timeseries: records}
+	data := snappy.Encode(nil, wr.MarshalProtobuf(nil))
+	app.sendBlocking(t, len(records), func() {
+		app.cli.Post(t, url, "application/x-protobuf", data, http.StatusNoContent)
+	})
+}
+
 // PrometheusAPIV1ImportPrometheus is a test helper function that inserts a
 // collection of records in Prometheus text exposition format for the given
 // tenant by sending a HTTP POST request to
@@ -56,9 +73,10 @@ func (app *Vminsert) PrometheusAPIV1ImportPrometheus(t *testing.T, records []str
 	t.Helper()
 
 	url := fmt.Sprintf("http://%s/insert/%s/prometheus/api/v1/import/prometheus", app.httpListenAddr, opts.Tenant)
-	wantRowsSentCount := app.rpcRowsSentTotal(t) + len(records)
+	data := []byte(strings.Join(records, "\n"))
-	app.cli.Post(t, url, "text/plain", strings.Join(records, "\n"), http.StatusNoContent)
+	app.sendBlocking(t, len(records), func() {
-	app.waitUntilSent(t, wantRowsSentCount)
+		app.cli.Post(t, url, "text/plain", data, http.StatusNoContent)
+	})
 }
 
 // String returns the string representation of the vminsert app state.
@@ -66,21 +84,29 @@ func (app *Vminsert) String() string {
 	return fmt.Sprintf("{app: %s httpListenAddr: %q}", app.app, app.httpListenAddr)
 }
 
-// waitUntilSent waits until vminsert sends buffered data to vmstorage.
+// sendBlocking sends the data to vmstorage by executing `send` function and
+// waits until the data is actually sent.
+//
+// vminsert does not send the data immediately. It first puts the data into a
+// buffer. Then a background goroutine takes the data from the buffer sends it
+// to the vmstorage. This happens every 200ms.
 //
 // Waiting is implemented a retrieving the value of `vm_rpc_rows_sent_total`
 // metric and checking whether it is equal or greater than the wanted value.
 // If it is, then the data has been sent to vmstorage.
 //
 // Unreliable if the records are inserted concurrently.
-func (app *Vminsert) waitUntilSent(t *testing.T, wantRowsSentCount int) {
+// TODO(rtm0): Put sending and waiting into a critical section to make reliable?
+func (app *Vminsert) sendBlocking(t *testing.T, numRecordsToSend int, send func()) {
 	t.Helper()
 
+	send()
+
 	const (
 		retries = 20
 		period  = 100 * time.Millisecond
 	)
-
+	wantRowsSentCount := app.rpcRowsSentTotal(t) + numRecordsToSend
 	for range retries {
 		if app.rpcRowsSentTotal(t) >= wantRowsSentCount {
 			return

apptest/vmselect.go

@@ -55,9 +55,28 @@ func (app *Vmselect) ClusternativeListenAddr() string {
 	return app.clusternativeListenAddr
 }
 
+// PrometheusAPIV1Export is a test helper function that performs the export of
+// raw samples in JSON line format by sending a HTTP POST request to
+// /prometheus/api/v1/export vmselect endpoint.
+//
+// See https://docs.victoriametrics.com/url-examples/#apiv1export
+func (app *Vmselect) PrometheusAPIV1Export(t *testing.T, query, start, end string, opts QueryOpts) *PrometheusAPIV1QueryResponse {
+	t.Helper()
+
+	exportURL := fmt.Sprintf("http://%s/select/%s/prometheus/api/v1/export", app.httpListenAddr, opts.Tenant)
+	values := url.Values{}
+	values.Add("match[]", query)
+	values.Add("start", start)
+	values.Add("end", end)
+	values.Add("timeout", opts.Timeout)
+	values.Add("format", "promapi")
+	res := app.cli.PostForm(t, exportURL, values, http.StatusOK)
+	return NewPrometheusAPIV1QueryResponse(t, res)
+}
+
 // PrometheusAPIV1Query is a test helper function that performs PromQL/MetricsQL
 // instant query by sending a HTTP POST request to /prometheus/api/v1/query
-// vmsingle endpoint.
+// vmselect endpoint.
 //
 // See https://docs.victoriametrics.com/url-examples/#apiv1query
 func (app *Vmselect) PrometheusAPIV1Query(t *testing.T, query, time, step string, opts QueryOpts) *PrometheusAPIV1QueryResponse {
@@ -75,7 +94,7 @@ func (app *Vmselect) PrometheusAPIV1Query(t *testing.T, query, time, step string
 
 // PrometheusAPIV1QueryRange is a test helper function that performs
 // PromQL/MetricsQL range query by sending a HTTP POST request to
-// /prometheus/api/v1/query_range vmsingle endpoint.
+// /prometheus/api/v1/query_range vmselect endpoint.
 //
 // See https://docs.victoriametrics.com/url-examples/#apiv1query_range
 func (app *Vmselect) PrometheusAPIV1QueryRange(t *testing.T, query, start, end, step string, opts QueryOpts) *PrometheusAPIV1QueryResponse {

apptest/vmsingle.go

@@ -9,6 +9,9 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	pb "github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
+	"github.com/golang/snappy"
 )
 
 // Vmsingle holds the state of a vmsingle app and provides vmsingle-specific
@@ -20,8 +23,15 @@ type Vmsingle struct {
 	storageDataPath string
 	httpListenAddr  string
 
+	// vmstorage URLs.
 	forceFlushURL string
+
+	// vminsert URLs.
 	prometheusAPIV1ImportPrometheusURL string
+	prometheusAPIV1WriteURL            string
+
+	// vmselect URLs.
+	prometheusAPIV1ExportURL     string
 	prometheusAPIV1QueryURL      string
 	prometheusAPIV1QueryRangeURL string
 	prometheusAPIV1SeriesURL     string
@@ -56,6 +66,8 @@ func StartVmsingle(instance string, flags []string, cli *Client) (*Vmsingle, err
 
 		forceFlushURL:                      fmt.Sprintf("http://%s/internal/force_flush", stderrExtracts[1]),
 		prometheusAPIV1ImportPrometheusURL: fmt.Sprintf("http://%s/prometheus/api/v1/import/prometheus", stderrExtracts[1]),
+		prometheusAPIV1WriteURL:            fmt.Sprintf("http://%s/prometheus/api/v1/write", stderrExtracts[1]),
+		prometheusAPIV1ExportURL:           fmt.Sprintf("http://%s/prometheus/api/v1/export", stderrExtracts[1]),
 		prometheusAPIV1QueryURL:            fmt.Sprintf("http://%s/prometheus/api/v1/query", stderrExtracts[1]),
 		prometheusAPIV1QueryRangeURL:       fmt.Sprintf("http://%s/prometheus/api/v1/query_range", stderrExtracts[1]),
 		prometheusAPIV1SeriesURL:           fmt.Sprintf("http://%s/prometheus/api/v1/series", stderrExtracts[1]),
@@ -70,6 +82,17 @@ func (app *Vmsingle) ForceFlush(t *testing.T) {
 	app.cli.Get(t, app.forceFlushURL, http.StatusOK)
 }
 
+// PrometheusAPIV1Write is a test helper function that inserts a
+// collection of records in Prometheus remote-write format by sending a HTTP
+// POST request to /prometheus/api/v1/write vmsingle endpoint.
+func (app *Vmsingle) PrometheusAPIV1Write(t *testing.T, records []pb.TimeSeries, _ QueryOpts) {
+	t.Helper()
+
+	wr := pb.WriteRequest{Timeseries: records}
+	data := snappy.Encode(nil, wr.MarshalProtobuf(nil))
+	app.cli.Post(t, app.prometheusAPIV1WriteURL, "application/x-protobuf", data, http.StatusNoContent)
+}
+
 // PrometheusAPIV1ImportPrometheus is a test helper function that inserts a
 // collection of records in Prometheus text exposition format by sending a HTTP
 // POST request to /prometheus/api/v1/import/prometheus vmsingle endpoint.
@@ -78,7 +101,26 @@ func (app *Vmsingle) ForceFlush(t *testing.T) {
 func (app *Vmsingle) PrometheusAPIV1ImportPrometheus(t *testing.T, records []string, _ QueryOpts) {
 	t.Helper()
 
-	app.cli.Post(t, app.prometheusAPIV1ImportPrometheusURL, "text/plain", strings.Join(records, "\n"), http.StatusNoContent)
+	data := []byte(strings.Join(records, "\n"))
+	app.cli.Post(t, app.prometheusAPIV1ImportPrometheusURL, "text/plain", data, http.StatusNoContent)
+}
+
+// PrometheusAPIV1Export is a test helper function that performs the export of
+// raw samples in JSON line format by sending a HTTP POST request to
+// /prometheus/api/v1/export vmsingle endpoint.
+//
+// See https://docs.victoriametrics.com/url-examples/#apiv1export
+func (app *Vmsingle) PrometheusAPIV1Export(t *testing.T, query, start, end string, opts QueryOpts) *PrometheusAPIV1QueryResponse {
+	t.Helper()
+
+	values := url.Values{}
+	values.Add("match[]", query)
+	values.Add("start", start)
+	values.Add("end", end)
+	values.Add("timeout", opts.Timeout)
+	values.Add("format", "promapi")
+	res := app.cli.PostForm(t, app.prometheusAPIV1ExportURL, values, http.StatusOK)
+	return NewPrometheusAPIV1QueryResponse(t, res)
 }
 
 // PrometheusAPIV1Query is a test helper function that performs PromQL/MetricsQL