extract search flags/limits into a separate lib for reusing

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

app/vmselect/graphite/metrics_api.go

@@ -1,7 +1,6 @@
 package graphite
 
 import (
-	"flag"
 	"fmt"
 	"math"
 	"net/http"
@@ -15,14 +14,13 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmselect/searchutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bufferedwriter"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httputil"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/limits"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/storage"
 	"github.com/VictoriaMetrics/metrics"
 	"github.com/VictoriaMetrics/metricsql"
 )
 
-var maxTagValueSuffixes = flag.Int("search.maxTagValueSuffixesPerSearch", 100e3, "The maximum number of tag value suffixes returned from /metrics/find")
-
 // MetricsFindHandler implements /metrics/find handler.
 //
 // See https://graphite-api.readthedocs.io/en/latest/api.html#metrics-find
@@ -222,10 +220,11 @@ func MetricsIndexHandler(startTime time.Time, w http.ResponseWriter, r *http.Req
 
 // metricsFind searches for label values that match the given qHead and qTail.
 func metricsFind(tr storage.TimeRange, label, qHead, qTail string, delimiter byte, isExpand bool, deadline searchutil.Deadline) ([]string, error) {
+	maxSuffixes := limits.MaxTagValueSuffixes(0)
 	n := strings.IndexAny(qTail, "*{[")
 	if n < 0 {
 		query := qHead + qTail
-		suffixes, err := netstorage.TagValueSuffixes(nil, tr, label, query, delimiter, *maxTagValueSuffixes, deadline)
+		suffixes, err := netstorage.TagValueSuffixes(nil, tr, label, query, delimiter, maxSuffixes, deadline)
 		if err != nil {
 			return nil, err
 		}
@@ -245,7 +244,7 @@ func metricsFind(tr storage.TimeRange, label, qHead, qTail string, delimiter byt
 	}
 	if n == len(qTail)-1 && strings.HasSuffix(qTail, "*") {
 		query := qHead + qTail[:len(qTail)-1]
-		suffixes, err := netstorage.TagValueSuffixes(nil, tr, label, query, delimiter, *maxTagValueSuffixes, deadline)
+		suffixes, err := netstorage.TagValueSuffixes(nil, tr, label, query, delimiter, maxSuffixes, deadline)
 		if err != nil {
 			return nil, err
 		}

app/vmselect/main.go

@@ -21,11 +21,11 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmselect/stats"
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmstorage"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/buildinfo"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/cgroup"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/flagutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fs"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httpserver"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httputil"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/limits"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/querytracer"
@@ -36,12 +36,6 @@ var (
 	deleteAuthKey                = flagutil.NewPassword("deleteAuthKey", "authKey for metrics' deletion via /api/v1/admin/tsdb/delete_series and /tags/delSeries. It could be passed via authKey query arg. It overrides -httpAuth.*")
 	metricNamesStatsResetAuthKey = flagutil.NewPassword("metricNamesStatsResetAuthKey", "authKey for resetting metric names usage cache via /api/v1/admin/status/metric_names_stats/reset. It overrides -httpAuth.*. "+
 		"See https://docs.victoriametrics.com/victoriametrics/single-server-victoriametrics/#track-ingested-metrics-usage")
-
-	maxConcurrentRequests = flag.Int("search.maxConcurrentRequests", getDefaultMaxConcurrentRequests(), "The maximum number of concurrent search requests. "+
-		"It shouldn't be high, since a single request can saturate all the CPU cores, while many concurrently executed requests may require high amounts of memory. "+
-		"See also -search.maxQueueDuration and -search.maxMemoryPerQuery")
-	maxQueueDuration = flag.Duration("search.maxQueueDuration", 10*time.Second, "The maximum time the request waits for execution when -search.maxConcurrentRequests "+
-		"limit is reached; see also -search.maxQueryDuration")
 	resetCacheAuthKey    = flagutil.NewPassword("search.resetCacheAuthKey", "Optional authKey for resetting rollup cache via /internal/resetRollupResultCache call. It could be passed via authKey query arg. It overrides -httpAuth.*")
 	logSlowQueryDuration = flag.Duration("search.logSlowQueryDuration", 5*time.Second, "Log queries with execution time exceeding this value. Zero disables slow query logging. "+
 		"See also -search.logQueryMemoryUsage")
@@ -50,23 +44,14 @@ var (
 
 var slowQueries = metrics.NewCounter(`vm_slow_queries_total`)
 
-func getDefaultMaxConcurrentRequests() int {
-	// A single request can saturate all the CPU cores, so there is no sense
-	// in allowing higher number of concurrent requests - they will just contend
-	// for unavailable CPU time.
-	n := min(cgroup.AvailableCPUs()*2, 16)
-	return n
-}
-
 // Init initializes vmselect
 func Init() {
 	tmpDirPath := *vmstorage.DataPath + "/tmp"
 	fs.MustRemoveDirContents(tmpDirPath)
 	netstorage.InitTmpBlocksDir(tmpDirPath)
 	promql.InitRollupResultCache(*vmstorage.DataPath + "/cache/rollupResult")
-	prometheus.InitMaxUniqueTimeseries(*maxConcurrentRequests)
 
-	concurrencyLimitCh = make(chan struct{}, *maxConcurrentRequests)
+	concurrencyLimitCh = make(chan struct{}, limits.MaxConcurrentRequests())
 	initVMUIConfig()
 	initVMAlertProxy()
 }
@@ -89,7 +74,7 @@ var (
 		return float64(len(concurrencyLimitCh))
 	})
 	_ = metrics.NewGauge(`vm_search_max_unique_timeseries`, func() float64 {
-		return float64(prometheus.GetMaxUniqueTimeSeries())
+		return float64(limits.MaxUniqueTimeseries())
 	})
 )
 
@@ -129,12 +114,12 @@ func RequestHandler(w http.ResponseWriter, r *http.Request) bool {
 	default:
 		// Sleep for a while until giving up. This should resolve short bursts in requests.
 		concurrencyLimitReached.Inc()
-		d := min(searchutil.GetMaxQueryDuration(r), *maxQueueDuration)
+		d := min(searchutil.GetMaxQueryDuration(r), limits.MaxQueueDuration())
 		t := timerpool.Get(d)
 		select {
 		case concurrencyLimitCh <- struct{}{}:
 			timerpool.Put(t)
-			qt.Printf("wait in queue because -search.maxConcurrentRequests=%d concurrent requests are executed", *maxConcurrentRequests)
+			qt.Printf("wait in queue because -%s=%d concurrent requests are executed", limits.MaxConcurrentRequestsFlagName(), limits.MaxConcurrentRequests())
 			defer func() { <-concurrencyLimitCh }()
 		case <-r.Context().Done():
 			timerpool.Put(t)
@@ -147,10 +132,11 @@ func RequestHandler(w http.ResponseWriter, r *http.Request) bool {
 			timerpool.Put(t)
 			concurrencyLimitTimeout.Inc()
 			err := &httpserver.ErrorWithStatusCode{
-				Err: fmt.Errorf("couldn't start executing the request in %.3f seconds, since -search.maxConcurrentRequests=%d concurrent requests "+
+				Err: fmt.Errorf("couldn't start executing the request in %.3f seconds, since -%s=%d concurrent requests "+
-					"are executed. Possible solutions: to reduce query load; to add more compute resources to the server; "+
+					"are already executed. Possible solutions: to reduce the query load; to add more compute resources to the server; "+
-					"to increase -search.maxQueueDuration=%s; to increase -search.maxQueryDuration; to increase -search.maxConcurrentRequests",
+					"to increase -%s=%d; to increase -%s",
-					d.Seconds(), *maxConcurrentRequests, maxQueueDuration),
+					d.Seconds(), limits.MaxConcurrentRequestsFlagName(), limits.MaxConcurrentRequests(),
+					limits.MaxQueueDurationFlagName(), limits.MaxQueueDuration(), limits.MaxConcurrentRequestsFlagName()),
 				StatusCode: http.StatusTooManyRequests,
 			}
 			w.Header().Add("Retry-After", "10")

app/vmselect/netstorage/netstorage.go

@@ -20,6 +20,7 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/cgroup"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/limits"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/querytracer"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/storage"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/storage/metricnamestats"
@@ -27,10 +28,6 @@ import (
 )
 
 var (
-	maxTagKeysPerSearch = flag.Int("search.maxTagKeys", 100e3, "The maximum number of tag keys returned from /api/v1/labels . "+
-		"See also -search.maxLabelsAPISeries and -search.maxLabelsAPIDuration")
-	maxTagValuesPerSearch = flag.Int("search.maxTagValues", 100e3, "The maximum number of tag values returned from /api/v1/label/<label_name>/values . "+
-		"See also -search.maxLabelsAPISeries and -search.maxLabelsAPIDuration")
 	maxSamplesPerSeries = flag.Int("search.maxSamplesPerSeries", 30e6, "The maximum number of raw samples a single query can scan per each time series. This option allows limiting memory usage")
 	maxSamplesPerQuery  = flag.Int("search.maxSamplesPerQuery", 1e9, "The maximum number of raw samples a single query can process across all time series. "+
 		"This protects from heavy queries, which select unexpectedly high number of raw samples. See also -search.maxSamplesPerSeries")
@@ -773,9 +770,8 @@ func LabelNames(qt *querytracer.Tracer, sq *storage.SearchQuery, maxLabelNames i
 	if deadline.Exceeded() {
 		return nil, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
-	if maxLabelNames > *maxTagKeysPerSearch || maxLabelNames <= 0 {
+
-		maxLabelNames = *maxTagKeysPerSearch
+	maxLabelNames = limits.MaxLabelNames(maxLabelNames)
-	}
 	tr := sq.GetTimeRange()
 	tfss, err := setupTfss(qt, tr, sq.TagFilterss, sq.MaxMetrics, deadline)
 	if err != nil {
@@ -841,9 +837,7 @@ func LabelValues(qt *querytracer.Tracer, labelName string, sq *storage.SearchQue
 	if deadline.Exceeded() {
 		return nil, fmt.Errorf("timeout exceeded before starting the query processing: %s", deadline.String())
 	}
-	if maxLabelValues > *maxTagValuesPerSearch || maxLabelValues <= 0 {
+	maxLabelValues = limits.MaxLabelValues(maxLabelValues)
-		maxLabelValues = *maxTagValuesPerSearch
-	}
 	tr := sq.GetTimeRange()
 	tfss, err := setupTfss(qt, tr, sq.TagFilterss, sq.MaxMetrics, deadline)
 	if err != nil {

app/vmselect/prometheus/prometheus.go

@@ -28,8 +28,7 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httpserver"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httputil"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/limits"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/memory"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/querytracer"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/storage"
@@ -50,9 +49,6 @@ var (
 		"If set to true, the query model becomes closer to InfluxDB data model. If set to true, then -search.maxLookback and -search.maxStalenessInterval are ignored")
 	maxStepForPointsAdjustment = flag.Duration("search.maxStepForPointsAdjustment", time.Minute, "The maximum step when /api/v1/query_range handler adjusts "+
 		"points with timestamps closer than -search.latencyOffset to the current time. The adjustment is needed because such points may contain incomplete data")
-
-	maxUniqueTimeseries = flag.Int("search.maxUniqueTimeseries", 0, "The maximum number of unique time series, which can be selected during /api/v1/query and /api/v1/query_range queries. This option allows limiting memory usage. "+
-		"When set to zero, the limit is automatically calculated based on -search.maxConcurrentRequests (inversely proportional) and memory available to the process (proportional).")
 	maxFederateSeries       = flag.Int("search.maxFederateSeries", 1e6, "The maximum number of time series, which can be returned from /federate. This option allows limiting memory usage")
 	maxExportSeries         = flag.Int("search.maxExportSeries", 10e6, "The maximum number of time series, which can be returned from /api/v1/export* APIs. This option allows limiting memory usage")
 	maxTSDBStatusSeries     = flag.Int("search.maxTSDBStatusSeries", 10e6, "The maximum number of time series, which can be processed during the call to /api/v1/status/tsdb. This option allows limiting memory usage")
@@ -853,7 +849,7 @@ func QueryHandler(qt *querytracer.Tracer, startTime time.Time, w http.ResponseWr
 		End:                 start,
 		Step:                step,
 		MaxPointsPerSeries:  *maxPointsPerTimeseries,
-		MaxSeries:           GetMaxUniqueTimeSeries(),
+		MaxSeries:           limits.MaxUniqueTimeseries(),
 		QuotedRemoteAddr:    httpserver.GetQuotedRemoteAddr(r),
 		Deadline:            deadline,
 		MayCache:            mayCache,
@@ -964,7 +960,7 @@ func queryRangeHandler(qt *querytracer.Tracer, startTime time.Time, w http.Respo
 		End:                 end,
 		Step:                step,
 		MaxPointsPerSeries:  *maxPointsPerTimeseries,
-		MaxSeries:           GetMaxUniqueTimeSeries(),
+		MaxSeries:           limits.MaxUniqueTimeseries(),
 		QuotedRemoteAddr:    httpserver.GetQuotedRemoteAddr(r),
 		Deadline:            deadline,
 		MayCache:            mayCache,
@@ -1300,43 +1296,6 @@ func (sw *scalableWriter) flush() error {
 	return sw.bw.Flush()
 }
 
-var (
-	maxUniqueTimeseriesValueOnce sync.Once
-	maxUniqueTimeseriesValue     int
-)
-
-// InitMaxUniqueTimeseries init the max metrics limit calculated by available resources.
-// The calculation is split into calculateMaxUniqueTimeSeriesForResource for unit testing.
-func InitMaxUniqueTimeseries(maxConcurrentRequests int) {
-	maxUniqueTimeseriesValueOnce.Do(func() {
-		maxUniqueTimeseriesValue = *maxUniqueTimeseries
-		if maxUniqueTimeseriesValue <= 0 {
-			maxUniqueTimeseriesValue = calculateMaxUniqueTimeSeriesForResource(maxConcurrentRequests, memory.Remaining())
-		}
-	})
-}
-
-// calculateMaxUniqueTimeSeriesForResource calculate the max metrics limit calculated by available resources.
-func calculateMaxUniqueTimeSeriesForResource(maxConcurrentRequests, remainingMemory int) int {
-	if maxConcurrentRequests <= 0 {
-		// This line should NOT be reached unless the user has set an incorrect `search.maxConcurrentRequests`.
-		// In such cases, fallback to unlimited.
-		logger.Warnf("limiting -search.maxUniqueTimeseries to %v because -search.maxConcurrentRequests=%d.", 2e9, maxConcurrentRequests)
-		return 2e9
-	}
-
-	// Calculate the max metrics limit for a single request in the worst-case concurrent scenario.
-	// The approximate size of 1 unique series that could occupy in the vmstorage is 200 bytes.
-	mts := remainingMemory / 200 / maxConcurrentRequests
-	logger.Infof("limiting -search.maxUniqueTimeseries to %d according to -search.maxConcurrentRequests=%d and remaining memory=%d bytes. To increase the limit, reduce -search.maxConcurrentRequests or increase memory available to the process.", mts, maxConcurrentRequests, remainingMemory)
-	return mts
-}
-
-// GetMaxUniqueTimeSeries returns the max metrics limit calculated by available resources.
-func GetMaxUniqueTimeSeries() int {
-	return maxUniqueTimeseriesValue
-}
-
 // copied from https://github.com/prometheus/common/blob/adea6285c1c7447fcb7bfdeb6abfc6eff893e0a7/model/metric.go#L483
 // it's not possible to use direct import due to increased binary size
 func unescapePrometheusLabelName(name string) string {

app/vmselect/prometheus/prometheus_test.go

@@ -4,7 +4,6 @@ import (
 	"math"
 	"net/http"
 	"reflect"
-	"runtime"
 	"testing"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmselect/netstorage"
@@ -230,29 +229,3 @@ func TestGetLatencyOffsetMillisecondsFailure(t *testing.T) {
 	}
 	f("http://localhost?latency_offset=foobar")
 }
-
-func TestCalculateMaxMetricsLimitByResource(t *testing.T) {
-	f := func(maxConcurrentRequest, remainingMemory, expect int) {
-		t.Helper()
-		maxMetricsLimit := calculateMaxUniqueTimeSeriesForResource(maxConcurrentRequest, remainingMemory)
-		if maxMetricsLimit != expect {
-			t.Fatalf("unexpected max metrics limit: got %d, want %d", maxMetricsLimit, expect)
-		}
-	}
-
-	// Skip when GOARCH=386
-	if runtime.GOARCH != "386" {
-		// 8 CPU & 32 GiB
-		f(16, int(math.Round(32*1024*1024*1024*0.4)), 4294967)
-		// 4 CPU & 32 GiB
-		f(8, int(math.Round(32*1024*1024*1024*0.4)), 8589934)
-	}
-
-	// 2 CPU & 4 GiB
-	f(4, int(math.Round(4*1024*1024*1024*0.4)), 2147483)
-
-	// other edge cases
-	f(0, int(math.Round(4*1024*1024*1024*0.4)), 2e9)
-	f(4, 0, 0)
-
-}

lib/limits/select.go

@@ -0,0 +1,141 @@
+package limits
+
+import (
+	"flag"
+	"sync"
+	"time"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/cgroup"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/memory"
+)
+
+var (
+	maxUniqueTimeseries = flag.Int("search.maxUniqueTimeseries", 0, "The maximum number of unique time series, which can be scanned during every query. "+
+		"This allows protecting against heavy queries, which select unexpectedly high number of series. When set to zero, the limit is automatically "+
+		"calculated based on -search.maxConcurrentRequests (inversely proportional) and memory available to the process (proportional). "+
+		"See also -search.max* command-line flags at vmselect")
+	maxLabelNames = flag.Int("search.maxTagKeys", 100e3, "The maximum number of tag keys returned per search. "+
+		"See also -search.maxLabelsAPISeries and -search.maxLabelsAPIDuration")
+	maxLabelValues = flag.Int("search.maxTagValues", 100e3, "The maximum number of tag values returned per search. "+
+		"See also -search.maxLabelsAPISeries and -search.maxLabelsAPIDuration")
+	maxTagValueSuffixes   = flag.Int("search.maxTagValueSuffixesPerSearch", 100e3, "The maximum number of tag value suffixes returned from /metrics/find")
+	maxConcurrentRequests = flag.Int("search.maxConcurrentRequests", defaultMaxConcurrentRequests(), "The maximum number of concurrent search requests. "+
+		"It shouldn't be high, since a single request can saturate all the CPU cores, while many concurrently executed requests may require high amounts of memory. "+
+		"See also -search.maxQueueDuration and -search.maxMemoryPerQuery")
+	maxQueueDuration = flag.Duration("search.maxQueueDuration", 10*time.Second, "The maximum time the incoming vmselect request waits for execution "+
+		"when -search.maxConcurrentRequests limit is reached")
+)
+
+func defaultMaxConcurrentRequests() int {
+	// A single request can saturate all the CPU cores, so there is no sense
+	// in allowing higher number of concurrent requests - they will just contend
+	// for unavailable CPU time.
+	n := min(cgroup.AvailableCPUs()*2, 16)
+	return n
+}
+
+// MaxConcurrentRequests returns the maximum number of concurrent requests
+// a server can process.
+//
+// The remaining requests wait for up to MaxQueueDuration for their execution.
+func MaxConcurrentRequests() int {
+	return *maxConcurrentRequests
+}
+
+// MaxConcurrentRequestsFlagName returns the name of the flag used for
+// configuring max number of concurrent search requests.
+func MaxConcurrentRequestsFlagName() string {
+	return "search.maxConcurrentRequests"
+}
+
+// MaxQueueDuration returns the maximum duration to wait if
+// MaxConcurrentRequests are executed.
+func MaxQueueDuration() time.Duration {
+	return *maxQueueDuration
+}
+
+// MaxQueueDurationFlagName returns the name of the flag used for configuring
+// the max time duration during which a search request may remain in queue.
+func MaxQueueDurationFlagName() string {
+	return "search.maxQueueDuration"
+}
+
+// MaxMetrics calculates the max number of metric names a single query is
+// allowed to return based on the limit from the search query and
+// -search.maxUniqueTimeseries flag value.
+func MaxMetrics(searchQueryLimit int) int {
+	if searchQueryLimit <= 0 {
+		return MaxUniqueTimeseries()
+	}
+	// searchQueryLimit cannot exceed `-search.maxUniqueTimeseries`
+	if *maxUniqueTimeseries != 0 && searchQueryLimit > *maxUniqueTimeseries {
+		searchQueryLimit = *maxUniqueTimeseries
+	}
+	return searchQueryLimit
+}
+
+// MaxLabelNames calculates the max number of label names a single query is
+// allowed to return based on the limit from the search query and
+// -search.maxTagKeys flag value.
+func MaxLabelNames(searchQueryLimit int) int {
+	return calculateLimit(searchQueryLimit, *maxLabelNames)
+}
+
+// MaxLabelValues calculates the max number of label values a single query is
+// allowed to return based on the limit from the search query and
+// -search.maxTagValues flag value.
+func MaxLabelValues(searchQueryLimit int) int {
+	return calculateLimit(searchQueryLimit, *maxLabelValues)
+}
+
+// MaxTagValueSuffixes calculates the max number of tag value suffixes a single
+// query is allowed to return based on the limit from the search query and
+// -search.maxTagValueSuffixesPerSearch flag value.
+func MaxTagValueSuffixes(searchQueryLimit int) int {
+	return calculateLimit(searchQueryLimit, *maxTagValueSuffixes)
+}
+
+func calculateLimit(searchQueryLimit, flagValue int) int {
+	if 0 < searchQueryLimit && searchQueryLimit < flagValue {
+		return searchQueryLimit
+	}
+	return flagValue
+}
+
+var (
+	maxUniqueTimeseriesValue     int
+	maxUniqueTimeseriesValueOnce sync.Once
+)
+
+// MaxUniqueTimeseries returns `-search.maxUniqueTimeseries` or the
+// auto-calculated value based on available resources.
+func MaxUniqueTimeseries() int {
+	maxUniqueTimeseriesValueOnce.Do(func() {
+		maxUniqueTimeseriesValue = *maxUniqueTimeseries
+		if maxUniqueTimeseriesValue <= 0 {
+			maxUniqueTimeseriesValue = calculateMaxUniqueTimeseries(*maxConcurrentRequests, memory.Remaining())
+		}
+	})
+	return maxUniqueTimeseriesValue
+}
+
+// calculateMaxUniqueTimeseries calculates the maxUniqueTimeseries limit based
+// on available resources.
+func calculateMaxUniqueTimeseries(maxConcurrentRequests, remainingMemory int) int {
+	if maxConcurrentRequests <= 0 {
+		// This line should NOT be reached unless the user has set an incorrect
+		// `-search.maxConcurrentRequests`. In such cases, fallback to
+		// unlimited.
+		logger.Warnf("limiting -search.maxUniqueTimeseries to %v because -search.maxConcurrentRequests=%d.", 2e9, maxConcurrentRequests)
+		return 2e9
+	}
+
+	// Calculate the maxUniqueTimeseries limit for a single request in the
+	// worst-case concurrent scenario. The approximate size of 1 unique series
+	// that could occupy in vmstorage is 200 bytes.
+	mts := remainingMemory / 200 / maxConcurrentRequests
+	logger.Infof("limiting -search.maxUniqueTimeseries to %d according to -search.maxConcurrentRequests=%d and remaining memory=%d bytes. "+
+		"To increase the limit, reduce -search.maxConcurrentRequests or increase memory available to the process.", mts, maxConcurrentRequests, remainingMemory)
+	return mts
+}

lib/limits/select_test.go

@@ -0,0 +1,52 @@
+package limits
+
+import (
+	"math"
+	"runtime"
+	"testing"
+)
+
+func TestCalculateMaxUniqueTimeseries(t *testing.T) {
+	f := func(maxConcurrentRequests, remainingMemory, want int) {
+		t.Helper()
+		got := calculateMaxUniqueTimeseries(maxConcurrentRequests, remainingMemory)
+		if got != want {
+			t.Fatalf("unexpected maxUniqueTimeseries: got %d, want %d", got, want)
+		}
+	}
+
+	// Skip when GOARCH=386
+	if runtime.GOARCH != "386" {
+		// 8 CPU & 32 GiB
+		f(16, int(math.Round(32*1024*1024*1024*0.4)), 4294967)
+		// 4 CPU & 32 GiB
+		f(8, int(math.Round(32*1024*1024*1024*0.4)), 8589934)
+	}
+
+	// 2 CPU & 4 GiB
+	f(4, int(math.Round(4*1024*1024*1024*0.4)), 2147483)
+
+	// other edge cases
+	f(0, int(math.Round(4*1024*1024*1024*0.4)), 2e9)
+	f(4, 0, 0)
+
+}
+
+func TestMaxMetrics(t *testing.T) {
+	originalMaxUniqueTimeseries := *maxUniqueTimeseries
+	defer func() {
+		*maxUniqueTimeseries = originalMaxUniqueTimeseries
+	}()
+	f := func(searchQueryLimit, flagLimit, want int) {
+		t.Helper()
+		*maxUniqueTimeseries = flagLimit
+		got := MaxMetrics(searchQueryLimit)
+		if got != want {
+			t.Fatalf("unexpected maxMetrics: got %d, want %d", got, want)
+		}
+	}
+
+	f(0, 1e6, 1e6)
+	f(2e6, 0, 2e6)
+	f(2e6, 1e6, 1e6)
+}