gocollector: Added options to Go Collector for diffetent collections.

Fixes #983

Also:

* fixed TestMemStatsEquivalence, it was noop before (:
* Removed gc_cpu_fraction metric completely, since it's not working completely for Go1.17+

Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>

prometheus/collectors/go_collector.go

@@ -15,6 +15,65 @@ package collectors
 
 import "github.com/prometheus/client_golang/prometheus"
 
+type goOptions = prometheus.GoCollectorOptions
+type goOption func(o *goOptions)
+
+type GoCollectionOption uint32
+
+const (
+	// GoRuntimeMemStatsCollection represents the metrics represented by runtime.MemStats structure such as
+	// go_memstats_alloc_bytes
+	// go_memstats_alloc_bytes_total
+	// go_memstats_sys_bytes
+	// go_memstats_lookups_total
+	// go_memstats_mallocs_total
+	// go_memstats_frees_total
+	// go_memstats_heap_alloc_bytes
+	// go_memstats_heap_sys_bytes
+	// go_memstats_heap_idle_bytes
+	// go_memstats_heap_inuse_bytes
+	// go_memstats_heap_released_bytes
+	// go_memstats_heap_objects
+	// go_memstats_stack_inuse_bytes
+	// go_memstats_stack_sys_bytes
+	// go_memstats_mspan_inuse_bytes
+	// go_memstats_mspan_sys_bytes
+	// go_memstats_mcache_inuse_bytes
+	// go_memstats_mcache_sys_bytes
+	// go_memstats_buck_hash_sys_bytes
+	// go_memstats_gc_sys_bytes
+	// go_memstats_other_sys_bytes
+	// go_memstats_next_gc_bytes
+	// so the metrics known from pre client_golang v1.12.0, except skipped go_memstats_gc_cpu_fraction (see
+	// https://github.com/prometheus/client_golang/issues/842#issuecomment-861812034 for explanation.
+	//
+	// NOTE that this mode represents runtime.MemStats statistics, but they are
+	// actually implemented using new runtime/metrics package.
+	// Deprecated: Use GoRuntimeMetricsCollection instead going forward.
+	GoRuntimeMemStatsCollection GoCollectionOption = 1 << iota
+	// GoRuntimeMetricsCollection is the new set of metrics represented by runtime/metrics package and follows
+	// consistent naming. The exposed metric set depends on Go version, but it is controlled against
+	// unexpected cardinality. This set has overlapping information with GoRuntimeMemStatsCollection, just with
+	// new names. GoRuntimeMetricsCollection is what is recommended for using going forward.
+	GoRuntimeMetricsCollection
+)
+
+// WithGoCollections allows enabling different collections for Go collector on top of base metrics
+// like go_goroutines, go_threads, go_gc_duration_seconds, go_memstats_last_gc_time_seconds, go_info.
+//
+// Check GoRuntimeMemStatsCollection and GoRuntimeMetricsCollection for more details. You can use none,
+// one or more collections at once. For example:
+// WithGoCollections(GoRuntimeMemStatsCollection | GoRuntimeMetricsCollection) means both GoRuntimeMemStatsCollection
+// metrics and GoRuntimeMetricsCollection will be exposed.
+//
+// Use WithGoCollections(GoRuntimeMemStatsCollection) to have Go collector working in
+// the compatibility mode with client_golang pre v1.12 (move to runtime/metrics).
+func WithGoCollections(flags uint32) goOption {
+	return func(o *goOptions) {
+		o.EnabledCollections = flags
+	}
+}
+
 // NewGoCollector returns a collector that exports metrics about the current Go
 // process. This includes memory stats. To collect those, runtime.ReadMemStats
 // is called. This requires to “stop the world”, which usually only happens for
@@ -41,9 +100,13 @@ import "github.com/prometheus/client_golang/prometheus"
 //
 // NOTE: The problem is solved in Go 1.15, see
 // https://github.com/golang/go/issues/19812 for the related Go issue.
-func NewGoCollector() prometheus.Collector {
+func NewGoCollector(opts ...goOption) prometheus.Collector {
+	promPkgOpts := make([]func(o *prometheus.GoCollectorOptions), len(opts))
+	for i, opt := range opts {
+		promPkgOpts[i] = opt
+	}
 	//nolint:staticcheck // Ignore SA1019 until v2.
-	return prometheus.NewGoCollector()
+	return prometheus.NewGoCollector(promPkgOpts...)
 }
 
 // NewBuildInfoCollector returns a collector collecting a single metric

prometheus/go_collector.go

@@ -197,14 +197,6 @@ func goRuntimeMemStats() memStatsMetrics {
 			),
 			eval:    func(ms *runtime.MemStats) float64 { return float64(ms.NextGC) },
 			valType: GaugeValue,
-		}, {
-			desc: NewDesc(
-				memstatNamespace("gc_cpu_fraction"),
-				"The fraction of this program's available CPU time used by the GC since the program started.",
-				nil, nil,
-			),
-			eval:    func(ms *runtime.MemStats) float64 { return ms.GCCPUFraction },
-			valType: GaugeValue,
 		},
 	}
 }
@@ -268,7 +260,6 @@ func (c *baseGoCollector) Collect(ch chan<- Metric) {
 	quantiles[0.0] = stats.PauseQuantiles[0].Seconds()
 	ch <- MustNewConstSummary(c.gcDesc, uint64(stats.NumGC), stats.PauseTotal.Seconds(), quantiles)
 	ch <- MustNewConstMetric(c.gcLastTimeDesc, GaugeValue, float64(stats.LastGC.UnixNano())/1e9)
-
 	ch <- MustNewConstMetric(c.goInfoDesc, GaugeValue, 1)
 }
 
@@ -278,6 +269,7 @@ func memstatNamespace(s string) string {
 
 // memStatsMetrics provide description, evaluator, runtime/metrics name, and
 // value type for memstat metrics.
+// TODO(bwplotka): Remove with end Go 1.16 EOL and replace with runtime/metrics.Description
 type memStatsMetrics []struct {
 	desc    *Desc
 	eval    func(*runtime.MemStats) float64

prometheus/go_collector_go116.go

@@ -40,13 +40,28 @@ type goCollector struct {
 //
 // Deprecated: Use collectors.NewGoCollector instead.
 func NewGoCollector() Collector {
+	msMetrics := goRuntimeMemStats()
+	msMetrics = append(msMetrics, struct {
+		desc    *Desc
+		eval    func(*runtime.MemStats) float64
+		valType ValueType
+	}{
+		// This metric is omitted in Go1.17+, see https://github.com/prometheus/client_golang/issues/842#issuecomment-861812034
+		desc: NewDesc(
+			memstatNamespace("gc_cpu_fraction"),
+			"The fraction of this program's available CPU time used by the GC since the program started.",
+			nil, nil,
+		),
+		eval:    func(ms *runtime.MemStats) float64 { return ms.GCCPUFraction },
+		valType: GaugeValue,
+	})
 	return &goCollector{
 		base:      newBaseGoCollector(),
 		msLast:    &runtime.MemStats{},
 		msRead:    runtime.ReadMemStats,
 		msMaxWait: time.Second,
 		msMaxAge:  5 * time.Minute,
-		msMetrics: goRuntimeMemStats(),
+		msMetrics: msMetrics,
 	}
 }