meter: rework meter interface

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

meter/meter.go

@@ -0,0 +1,62 @@
+// Package meter is for instrumentation
+package meter
+
+import (
+	"time"
+
+	"github.com/unistack-org/micro/v3/metadata"
+)
+
+var (
+	DefaultReporter Meter = NewMeter()
+)
+
+// Meter is an interface for collecting and instrumenting metrics
+type Meter interface {
+	Init(...Option) error
+	Counter(string, metadata.Metadata) Counter
+	FloatCounter(string, metadata.Metadata) FloatCounter
+	Gauge(string, func() float64, metadata.Metadata) Gauge
+	Set(metadata.Metadata) Meter
+	Histogram(string, metadata.Metadata) Histogram
+	Summary(string, metadata.Metadata) Summary
+	SummaryExt(string, time.Duration, []float64, metadata.Metadata) Summary
+	Options() Options
+	String() string
+}
+
+// Counter is a counter
+type Counter interface {
+	Add(int)
+	Dec()
+	Get() uint64
+	Inc()
+	Set(uint64)
+}
+
+// FloatCounter is a float64 counter
+type FloatCounter interface {
+	Add(float64)
+	Get() float64
+	Set(float64)
+	Sub(float64)
+}
+
+// Gauge is a float64 gauge
+type Gauge interface {
+	Get() float64
+}
+
+// Histogram is a histogram for non-negative values with automatically created buckets
+type Histogram interface {
+	Reset()
+	Update(float64)
+	UpdateDuration(time.Time)
+	// VisitNonZeroBuckets(f func(vmrange string, count uint64))
+}
+
+// Summary is the summary
+type Summary interface {
+	Update(float64)
+	UpdateDuration(time.Time)
+}