Add Aggregation.Kind()

sdk/export/metric/aggregation/aggregation.go

@@ -27,6 +27,9 @@ import (
 type (
 	// Aggregation is an interface returned by the Aggregator
 	// containing an interval of metric data.
+	//
+	// Note that the interfaces below do not embed this interface.
+	// Aggregators are expected to
 	Aggregation interface {
 		// Kind returns a short identifying string to identify
 		// the Aggregator that was used to produce the
@@ -36,37 +39,44 @@ type (
 
 	// Sum returns an aggregated sum.
 	Sum interface {
+		Aggregation
 		Sum() (metric.Number, error)
 	}
 
 	// Sum returns the number of values that were aggregated.
 	Count interface {
+		Aggregation
 		Count() (int64, error)
 	}
 
 	// Min returns the minimum value over the set of values that were aggregated.
 	Min interface {
+		Aggregation
 		Min() (metric.Number, error)
 	}
 
 	// Max returns the maximum value over the set of values that were aggregated.
 	Max interface {
+		Aggregation
 		Max() (metric.Number, error)
 	}
 
 	// Quantile returns an exact or estimated quantile over the
 	// set of values that were aggregated.
 	Quantile interface {
+		Aggregation
 		Quantile(float64) (metric.Number, error)
 	}
 
 	// LastValue returns the latest value that was aggregated.
 	LastValue interface {
+		Aggregation
 		LastValue() (metric.Number, time.Time, error)
 	}
 
 	// Points returns the raw set of values that were aggregated.
 	Points interface {
+		Aggregation
 		Points() ([]metric.Number, error)
 	}
 
@@ -87,23 +97,29 @@ type (
 
 	// Histogram returns the count of events in pre-determined buckets.
 	Histogram interface {
-		Sum
+		Aggregation
+		Sum() (metric.Number, error)
 		Histogram() (Buckets, error)
 	}
 
 	// MinMaxSumCount supports the Min, Max, Sum, and Count interfaces.
 	MinMaxSumCount interface {
-		Min
-		Max
-		Sum
-		Count
+		Aggregation
+		Min() (metric.Number, error)
+		Max() (metric.Number, error)
+		Sum() (metric.Number, error)
+		Count() (int64, error)
 	}
 
 	// Distribution supports the Min, Max, Sum, Count, and Quantile
 	// interfaces.
 	Distribution interface {
-		MinMaxSumCount
-		Quantile
+		Aggregation
+		Min() (metric.Number, error)
+		Max() (metric.Number, error)
+		Sum() (metric.Number, error)
+		Count() (int64, error)
+		Quantile(float64) (metric.Number, error)
 	}
 )
 

sdk/metric/aggregator/array/array.go

@@ -53,6 +53,11 @@ func New() *Aggregator {
 	return &Aggregator{}
 }
 
+// Kind returns aggregation.ExactKind.
+func (c *Aggregator) Kind() aggregation.Kind {
+	return aggregation.ExactKind
+}
+
 // Sum returns the sum of values in the checkpoint.
 func (c *Aggregator) Sum() (metric.Number, error) {
 	return c.ckptSum, nil

sdk/metric/aggregator/ddsketch/ddsketch.go

@@ -52,6 +52,11 @@ func New(desc *metric.Descriptor, cfg *Config) *Aggregator {
 	}
 }
 
+// Kind returns aggregation.SketchKind.
+func (c *Aggregator) Kind() aggregation.Kind {
+	return aggregation.SketchKind
+}
+
 // NewDefaultConfig returns a new, default DDSketch config.
 //
 // TODO: Should the Config constructor set minValue to -Inf to

sdk/metric/aggregator/histogram/histogram.go

@@ -80,6 +80,11 @@ func New(desc *metric.Descriptor, boundaries []float64) *Aggregator {
 	}
 }
 
+// Kind returns aggregation.HistogramKind.
+func (c *Aggregator) Kind() aggregation.Kind {
+	return aggregation.HistogramKind
+}
+
 // Sum returns the sum of all values in the checkpoint.
 func (c *Aggregator) Sum() (metric.Number, error) {
 	c.lock.Lock()

sdk/metric/aggregator/lastvalue/lastvalue.go

@@ -68,6 +68,11 @@ func New() *Aggregator {
 	}
 }
 
+// Kind returns aggregation.LastValueKind.
+func (g *Aggregator) Kind() aggregation.Kind {
+	return aggregation.LastValueKind
+}
+
 // LastValue returns the last-recorded lastValue value and the
 // corresponding timestamp.  The error value aggregation.ErrNoData
 // will be returned if (due to a race condition) the checkpoint was

sdk/metric/aggregator/minmaxsumcount/mmsc.go

@@ -63,6 +63,11 @@ func New(desc *metric.Descriptor) *Aggregator {
 	}
 }
 
+// Kind returns aggregation.MinMaxSumCountKind.
+func (c *Aggregator) Kind() aggregation.Kind {
+	return aggregation.MinMaxSumCountKind
+}
+
 // Sum returns the sum of values in the checkpoint.
 func (c *Aggregator) Sum() (metric.Number, error) {
 	c.lock.Lock()

sdk/metric/aggregator/sum/sum.go

@@ -44,6 +44,11 @@ func New() *Aggregator {
 	return &Aggregator{}
 }
 
+// Kind returns aggregation.SumKind.
+func (c *Aggregator) Kind() aggregation.Kind {
+	return aggregation.SumKind
+}
+
 // Sum returns the last-checkpointed sum.  This will never return an
 // error.
 func (c *Aggregator) Sum() (metric.Number, error) {