Merge pull request #222 from lightstep/jmacd/factorhisto

Factor the exponential histogram into a re-usable package

lightstep/sdk/metric/README.md

@@ -16,7 +16,7 @@ however it is not covered by any stability guarantee.
 
 Differences from the OpenTelemetry metrics SDK specification:
 
-1. [ExponentialHistogram](./aggregator/histogram/README.md) is the
+1. [ExponentialHistogram](./aggregator/histogram/structure/README.md) is the
    default aggregation for Histogram instruments.  The
    explicit-boundary histogram aggregation is not supported.
 2. [MinMaxSumCount](./aggregator/minmaxsumcount/README.md) is an

lightstep/sdk/metric/aggregator/aggregator.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 
 	"github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/aggregator/aggregation"
+	histostruct "github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/aggregator/histogram/structure"
 	"github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/number"
 	"github.com/lightstep/otel-launcher-go/lightstep/sdk/metric/sdkinstrument"
 	"go.opentelemetry.io/otel"
@@ -59,19 +60,40 @@ func RangeTest[N number.Any, Traits number.Traits[N]](num N, desc sdkinstrument.
 	return true
 }
 
-// HistogramConfig configures the exponential histogram.
-type HistogramConfig struct {
+// JSONHistogramConfig configures the exponential histogram.
+type JSONHistogramConfig struct {
 	MaxSize int32 `json:"max_size"`
 }
 
+// JSONConfig supports the configuration for all aggregators in a single struct.
+type JSONConfig struct {
+	Histogram JSONHistogramConfig `json:"histogram"`
+}
+
+// ToConfig returns a Config from the fixed-JSON represented.
+func (jc JSONConfig) ToConfig() Config {
+	return Config{
+		Histogram: histostruct.NewConfig(histostruct.WithMaxSize(jc.Histogram.MaxSize)),
+	}
+}
+
 // Config supports the configuration for all aggregators in a single struct.
 type Config struct {
-	Histogram HistogramConfig `json:"histogram"`
+	Histogram histostruct.Config
 }
 
 // Valid returns true for valid configurations.
 func (c Config) Valid() bool {
-	return c.Histogram.MaxSize == 0 || c.Histogram.MaxSize >= 2
+	_, err := c.Validate()
+	return err == nil
+}
+
+// Valid returns a valid Configuration along with an error if there
+// were invalid settings.  Note that the empty state is considered valid and a correct
+func (c Config) Validate() (Config, error) {
+	var err error
+	c.Histogram, err = c.Histogram.Validate()
+	return c, err
 }
 
 // Methods implements a specific aggregation behavior for a specific

lightstep/sdk/metric/aggregator/gauge/gauge.go

@@ -34,7 +34,7 @@ import (
 // colleciton path in this library.
 
 type (
-	Methods[N number.Any, Traits number.Traits[N], Storage State[N, Traits]] struct{}
+	Methods[N number.Any, Traits number.Traits[N]] struct{}
 
 	State[N number.Any, Traits number.Traits[N]] struct {
 		lock  sync.Mutex
@@ -45,8 +45,8 @@ type (
 	Int64   = State[int64, number.Int64Traits]
 	Float64 = State[float64, number.Float64Traits]
 
-	Int64Methods   = Methods[int64, number.Int64Traits, Int64]
-	Float64Methods = Methods[float64, number.Float64Traits, Float64]
+	Int64Methods   = Methods[int64, number.Int64Traits]
+	Float64Methods = Methods[float64, number.Float64Traits]
 )
 
 // initialSequence is the first assigned sequence number, also the
@@ -108,19 +108,19 @@ func (g *State[N, Traits]) SetSequenceForTesting() {
 	g.seq = initialSequence
 }
 
-func (Methods[N, Traits, Storage]) Kind() aggregation.Kind {
+func (Methods[N, Traits]) Kind() aggregation.Kind {
 	return aggregation.GaugeKind
 }
 
-func (Methods[N, Traits, Storage]) Init(state *State[N, Traits], _ aggregator.Config) {
+func (Methods[N, Traits]) Init(state *State[N, Traits], _ aggregator.Config) {
 	// Note: storage is zero to start
 }
 
-func (Methods[N, Traits, Storage]) HasChange(ptr *State[N, Traits]) bool {
+func (Methods[N, Traits]) HasChange(ptr *State[N, Traits]) bool {
 	return ptr.seq != 0
 }
 
-func (Methods[N, Traits, Storage]) Move(from, to *State[N, Traits]) {
+func (Methods[N, Traits]) Move(from, to *State[N, Traits]) {
 	from.lock.Lock()
 	defer from.lock.Unlock()
 
@@ -130,14 +130,14 @@ func (Methods[N, Traits, Storage]) Move(from, to *State[N, Traits]) {
 	from.seq = 0
 }
 
-func (Methods[N, Traits, Storage]) Copy(from, to *State[N, Traits]) {
+func (Methods[N, Traits]) Copy(from, to *State[N, Traits]) {
 	from.lock.Lock()
 	defer from.lock.Unlock()
 	to.value = from.value
 	to.seq = from.seq
 }
 
-func (Methods[N, Traits, Storage]) Update(state *State[N, Traits], number N) {
+func (Methods[N, Traits]) Update(state *State[N, Traits], number N) {
 	newSeq := atomic.AddUint64(&sequenceVar, 1)
 
 	state.lock.Lock()
@@ -147,7 +147,7 @@ func (Methods[N, Traits, Storage]) Update(state *State[N, Traits], number N) {
 	state.seq = newSeq
 }
 
-func (Methods[N, Traits, Storage]) Merge(from, to *State[N, Traits]) {
+func (Methods[N, Traits]) Merge(from, to *State[N, Traits]) {
 	to.lock.Lock()
 	defer to.lock.Unlock()
 
@@ -157,15 +157,15 @@ func (Methods[N, Traits, Storage]) Merge(from, to *State[N, Traits]) {
 	}
 }
 
-func (Methods[N, Traits, Storage]) ToAggregation(state *State[N, Traits]) aggregation.Aggregation {
+func (Methods[N, Traits]) ToAggregation(state *State[N, Traits]) aggregation.Aggregation {
 	return state
 }
 
-func (Methods[N, Traits, Storage]) ToStorage(aggr aggregation.Aggregation) (*State[N, Traits], bool) {
+func (Methods[N, Traits]) ToStorage(aggr aggregation.Aggregation) (*State[N, Traits], bool) {
 	r, ok := aggr.(*State[N, Traits])
 	return r, ok
 }
 
-func (Methods[N, Traits, Storage]) SubtractSwap(operand, argument *State[N, Traits]) {
+func (Methods[N, Traits]) SubtractSwap(operand, argument *State[N, Traits]) {
 	panic("not used for non-temporal metrics")
 }