all: use Gauge instead of Counter for *_config_last_reload_successful metrics

This allows exposing the correct TYPE metadata for these labels when the app runs with -metrics.exposeMetadata command-line flag.
See https://github.com/VictoriaMetrics/metrics/pull/61#issuecomment-1860085508 for more details.

This is follow-up for 326a77c697

app/vmagent/remotewrite/remotewrite.go

@@ -276,7 +276,7 @@ func reloadRelabelConfigs() {
 var (
 	relabelConfigReloads      = metrics.NewCounter(`vmagent_relabel_config_reloads_total`)
 	relabelConfigReloadErrors = metrics.NewCounter(`vmagent_relabel_config_reloads_errors_total`)
-	relabelConfigSuccess      = metrics.NewCounter(`vmagent_relabel_config_last_reload_successful`)
+	relabelConfigSuccess      = metrics.NewGauge(`vmagent_relabel_config_last_reload_successful`, nil)
 	relabelConfigTimestamp    = metrics.NewCounter(`vmagent_relabel_config_last_reload_success_timestamp_seconds`)
 )
 

app/vmalert/main.go

@@ -194,7 +194,7 @@ func main() {
 var (
 	configReloads      = metrics.NewCounter(`vmalert_config_last_reload_total`)
 	configReloadErrors = metrics.NewCounter(`vmalert_config_last_reload_errors_total`)
-	configSuccess      = metrics.NewCounter(`vmalert_config_last_reload_successful`)
+	configSuccess      = metrics.NewGauge(`vmalert_config_last_reload_successful`, nil)
 	configTimestamp    = metrics.NewCounter(`vmalert_config_last_reload_success_timestamp_seconds`)
 )
 

app/vmalert/main_test.go

@@ -141,7 +141,7 @@ groups:
 				t.Fatalf("expected to have config error %s; got nil instead", cErr)
 			}
 			if cfgSuc != 0 {
-				t.Fatalf("expected to have metric configSuccess to be set to 0; got %d instead", cfgSuc)
+				t.Fatalf("expected to have metric configSuccess to be set to 0; got %v instead", cfgSuc)
 			}
 			return
 		}
@@ -150,7 +150,7 @@ groups:
 			t.Fatalf("unexpected config error: %s", cErr)
 		}
 		if cfgSuc != 1 {
-			t.Fatalf("expected to have metric configSuccess to be set to 1; got %d instead", cfgSuc)
+			t.Fatalf("expected to have metric configSuccess to be set to 1; got %v instead", cfgSuc)
 		}
 	}
 

app/vmauth/auth_config.go

@@ -386,7 +386,7 @@ func (r *Regex) MarshalYAML() (interface{}, error) {
 var (
 	configReloads      = metrics.NewCounter(`vmauth_config_last_reload_total`)
 	configReloadErrors = metrics.NewCounter(`vmauth_config_last_reload_errors_total`)
-	configSuccess      = metrics.NewCounter(`vmauth_config_last_reload_successful`)
+	configSuccess      = metrics.NewGauge(`vmauth_config_last_reload_successful`, nil)
 	configTimestamp    = metrics.NewCounter(`vmauth_config_last_reload_success_timestamp_seconds`)
 )
 

app/vminsert/common/streamaggr.go

@@ -38,7 +38,7 @@ var (
 
 	saCfgReloads   = metrics.NewCounter(`vminsert_streamagg_config_reloads_total`)
 	saCfgReloadErr = metrics.NewCounter(`vminsert_streamagg_config_reloads_errors_total`)
-	saCfgSuccess   = metrics.NewCounter(`vminsert_streamagg_config_last_reload_successful`)
+	saCfgSuccess   = metrics.NewGauge(`vminsert_streamagg_config_last_reload_successful`, nil)
 	saCfgTimestamp = metrics.NewCounter(`vminsert_streamagg_config_last_reload_success_timestamp_seconds`)
 
 	sasGlobal atomic.Pointer[streamaggr.Aggregators]

app/vminsert/relabel/relabel.go

@@ -65,7 +65,7 @@ func Init() {
 var (
 	configReloads      = metrics.NewCounter(`vm_relabel_config_reloads_total`)
 	configReloadErrors = metrics.NewCounter(`vm_relabel_config_reloads_errors_total`)
-	configSuccess      = metrics.NewCounter(`vm_relabel_config_last_reload_successful`)
+	configSuccess      = metrics.NewGauge(`vm_relabel_config_last_reload_successful`, nil)
 	configTimestamp    = metrics.NewCounter(`vm_relabel_config_last_reload_success_timestamp_seconds`)
 )
 

go.mod

@@ -11,7 +11,7 @@ require (
 	// Do not use the original github.com/valyala/fasthttp because of issues
 	// like https://github.com/valyala/fasthttp/commit/996610f021ff45fdc98c2ce7884d5fa4e7f9199b
 	github.com/VictoriaMetrics/fasthttp v1.2.0
-	github.com/VictoriaMetrics/metrics v1.28.2
+	github.com/VictoriaMetrics/metrics v1.29.0
 	github.com/VictoriaMetrics/metricsql v0.70.0
 	github.com/aws/aws-sdk-go-v2 v1.24.0
 	github.com/aws/aws-sdk-go-v2/config v1.26.1

go.sum

@@ -63,8 +63,8 @@ github.com/VictoriaMetrics/fastcache v1.12.2/go.mod h1:AmC+Nzz1+3G2eCPapF6UcsnkT
 github.com/VictoriaMetrics/fasthttp v1.2.0 h1:nd9Wng4DlNtaI27WlYh5mGXCJOmee/2c2blTJwfyU9I=
 github.com/VictoriaMetrics/fasthttp v1.2.0/go.mod h1:zv5YSmasAoSyv8sBVexfArzFDIGGTN4TfCKAtAw7IfE=
 github.com/VictoriaMetrics/metrics v1.24.0/go.mod h1:eFT25kvsTidQFHb6U0oa0rTrDRdz4xTYjpL8+UPohys=
-github.com/VictoriaMetrics/metrics v1.28.2 h1:yWIq53N8G6hJI6vQ8I2NsiD4p+UsmQa/msLo3yqDfPQ=
-github.com/VictoriaMetrics/metrics v1.28.2/go.mod h1:r7hveu6xMdUACXvB8TYdAj8WEsKzWB0EkpJN+RDtOf8=
+github.com/VictoriaMetrics/metrics v1.29.0 h1:3qC+jcvymGJaQKt6wsXIlJieVFQwD/par9J1Bxul+Mc=
+github.com/VictoriaMetrics/metrics v1.29.0/go.mod h1:r7hveu6xMdUACXvB8TYdAj8WEsKzWB0EkpJN+RDtOf8=
 github.com/VictoriaMetrics/metricsql v0.70.0 h1:G0k/m1yAF6pmk0dM3VT9/XI5PZ8dL7EbcLhREf4bgeI=
 github.com/VictoriaMetrics/metricsql v0.70.0/go.mod h1:k4UaP/+CjuZslIjd+kCigNG9TQmUqh5v0TP/nMEy90I=
 github.com/VividCortex/ewma v1.2.0 h1:f58SaIzcDXrSy3kWaHNvuJgJ3Nmz59Zji6XoJR/q1ow=

lib/promscrape/scraper.go

@@ -202,7 +202,7 @@ var (
 	configMetricsSet   = metrics.NewSet()
 	configReloads      = configMetricsSet.NewCounter(`vm_promscrape_config_reloads_total`)
 	configReloadErrors = configMetricsSet.NewCounter(`vm_promscrape_config_reloads_errors_total`)
-	configSuccess      = configMetricsSet.NewCounter(`vm_promscrape_config_last_reload_successful`)
+	configSuccess      = configMetricsSet.NewGauge(`vm_promscrape_config_last_reload_successful`, nil)
 	configTimestamp    = configMetricsSet.NewCounter(`vm_promscrape_config_last_reload_success_timestamp_seconds`)
 )
 

vendor/github.com/VictoriaMetrics/metrics/gauge.go

@@ -3,10 +3,11 @@ package metrics
 import (
 	"fmt"
 	"io"
+	"math"
+	"sync/atomic"
 )
 
-// NewGauge registers and returns gauge with the given name, which calls f
-// to obtain gauge value.
+// NewGauge registers and returns gauge with the given name, which calls f to obtain gauge value.
 //
 // name must be valid Prometheus-compatible metric with possible labels.
 // For instance,
@@ -16,6 +17,7 @@ import (
 //   - foo{bar="baz",aaa="b"}
 //
 // f must be safe for concurrent calls.
+// if f is nil, then it is expected that the gauge value is changed via Gauge.Set() call.
 //
 // The returned gauge is safe to use from concurrent goroutines.
 //
@@ -25,19 +27,36 @@ func NewGauge(name string, f func() float64) *Gauge {
 }
 
 // Gauge is a float64 gauge.
-//
-// See also Counter, which could be used as a gauge with Set and Dec calls.
 type Gauge struct {
+	// f is a callback, which is called for returning the gauge value.
 	f func() float64
+
+	// valueBits contains uint64 representation of float64 passed to Gauge.Set.
+	valueBits uint64
 }
 
 // Get returns the current value for g.
 func (g *Gauge) Get() float64 {
-	return g.f()
+	if f := g.f; f != nil {
+		return f()
+	}
+	n := atomic.LoadUint64(&g.valueBits)
+	return math.Float64frombits(n)
+}
+
+// Set sets g value to v.
+//
+// The g must be created with nil callback in order to be able to call this function.
+func (g *Gauge) Set(v float64) {
+	if g.f != nil {
+		panic(fmt.Errorf("cannot call Set on gauge created with non-nil callback"))
+	}
+	n := math.Float64bits(v)
+	atomic.StoreUint64(&g.valueBits, n)
 }
 
 func (g *Gauge) marshalTo(prefix string, w io.Writer) {
-	v := g.f()
+	v := g.Get()
 	if float64(int64(v)) == v {
 		// Marshal integer values without scientific notation
 		fmt.Fprintf(w, "%s %d\n", prefix, int64(v))

vendor/github.com/VictoriaMetrics/metrics/set.go

@@ -251,9 +251,6 @@ func (s *Set) GetOrCreateFloatCounter(name string) *FloatCounter {
 //
 // The returned gauge is safe to use from concurrent goroutines.
 func (s *Set) NewGauge(name string, f func() float64) *Gauge {
-	if f == nil {
-		panic(fmt.Errorf("BUG: f cannot be nil"))
-	}
 	g := &Gauge{
 		f: f,
 	}
@@ -280,9 +277,6 @@ func (s *Set) GetOrCreateGauge(name string, f func() float64) *Gauge {
 	s.mu.Unlock()
 	if nm == nil {
 		// Slow path - create and register missing gauge.
-		if f == nil {
-			panic(fmt.Errorf("BUG: f cannot be nil"))
-		}
 		if err := validateMetric(name); err != nil {
 			panic(fmt.Errorf("BUG: invalid metric name %q: %s", name, err))
 		}

vendor/modules.txt

@@ -97,7 +97,7 @@ github.com/VictoriaMetrics/fastcache
 github.com/VictoriaMetrics/fasthttp
 github.com/VictoriaMetrics/fasthttp/fasthttputil
 github.com/VictoriaMetrics/fasthttp/stackless
-# github.com/VictoriaMetrics/metrics v1.28.2
+# github.com/VictoriaMetrics/metrics v1.29.0
 ## explicit; go 1.17
 github.com/VictoriaMetrics/metrics
 # github.com/VictoriaMetrics/metricsql v0.70.0