Move export types into trace and metric-specific subdirs (#289)

exporter/trace/jaeger/jaeger.go

@@ -24,7 +24,7 @@ import (
 
 	"go.opentelemetry.io/otel/api/core"
 	gen "go.opentelemetry.io/otel/exporter/trace/jaeger/internal/gen-go/jaeger"
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/trace"
 )
 
 const defaultServiceName = "OpenTelemetry"

exporter/trace/jaeger/jaeger_test.go

@@ -34,7 +34,7 @@ import (
 
 	"go.opentelemetry.io/otel/api/core"
 	gen "go.opentelemetry.io/otel/exporter/trace/jaeger/internal/gen-go/jaeger"
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/trace"
 )
 
 func TestNewExporter(t *testing.T) {

exporter/trace/stackdriver/stackdriver.go

@@ -26,7 +26,7 @@ import (
 	"google.golang.org/api/option"
 
 	"go.opentelemetry.io/otel/api/key"
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/trace"
 )
 
 // Option is function type that is passed to the exporter initialization function.

exporter/trace/stackdriver/trace.go

@@ -21,7 +21,7 @@ import (
 	traceclient "cloud.google.com/go/trace/apiv2"
 	tracepb "google.golang.org/genproto/googleapis/devtools/cloudtrace/v2"
 
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/trace"
 )
 
 // traceExporter is an imeplementation of trace.Exporter and trace.BatchExporter

exporter/trace/stackdriver/trace_proto.go

@@ -29,7 +29,7 @@ import (
 
 	"go.opentelemetry.io/otel/api/core"
 	opentelemetry "go.opentelemetry.io/otel/sdk"
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/trace"
 )
 
 const (

exporter/trace/stdout/stdout.go

@@ -20,7 +20,7 @@ import (
 	"io"
 	"os"
 
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/trace"
 )
 
 // Options are the options to be used when initializing a stdout export.

exporter/trace/stdout/stdout_test.go

@@ -26,7 +26,7 @@ import (
 	"go.opentelemetry.io/otel/api/core"
 	"go.opentelemetry.io/otel/api/key"
 	"go.opentelemetry.io/otel/api/trace"
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/trace"
 )
 
 func TestExporter_ExportSpan(t *testing.T) {

plugin/httptrace/clienttrace_test.go

@@ -26,7 +26,7 @@ import (
 	"go.opentelemetry.io/otel/api/key"
 	"go.opentelemetry.io/otel/global"
 	"go.opentelemetry.io/otel/plugin/httptrace"
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/trace"
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 )
 

sdk/export/metric.go → sdk/export/metric/metric.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package export
+package metric // import "go.opentelemetry.io/otel/sdk/export/metric"
 
 import (
 	"context"
@@ -21,26 +21,49 @@ import (
 	"go.opentelemetry.io/otel/api/unit"
 )
 
-// MetricAggregator implements a specific aggregation behavior, e.g.,
+// Batcher is responsible for deciding which kind of aggregation
+// to use and gathering exported results from the SDK.  The standard SDK
+// supports binding only one of these interfaces, i.e., a single exporter.
+//
+// Multiple-exporters could be implemented by implementing this interface
+// for a group of Batcher.
+type Batcher interface {
+	// AggregatorFor should return the kind of aggregator
+	// suited to the requested export.  Returning `nil`
+	// indicates to ignore the metric update.
+	//
+	// Note: This is context-free because the handle should not be
+	// bound to the incoming context.  This call should not block.
+	AggregatorFor(Record) Aggregator
+
+	// Export receives pairs of records and aggregators
+	// during the SDK Collect().  Exporter implementations
+	// must access the specific aggregator to receive the
+	// exporter data, since the format of the data varies
+	// by aggregation.
+	Export(context.Context, Record, Aggregator)
+}
+
+// Aggregator implements a specific aggregation behavior, e.g.,
 // a counter, a gauge, a histogram.
-type MetricAggregator interface {
+type Aggregator interface {
 	// Update receives a new measured value and incorporates it
 	// into the aggregation.
-	Update(context.Context, core.Number, MetricRecord)
+	Update(context.Context, core.Number, Record)
 
 	// Collect is called during the SDK Collect() to
 	// finish one period of aggregation.  Collect() is
 	// called in a single-threaded context.  Update()
 	// calls may arrive concurrently.
-	Collect(context.Context, MetricRecord, MetricBatcher)
+	Collect(context.Context, Record, Batcher)
 
 	// Merge combines state from two aggregators into one.
-	Merge(MetricAggregator, *Descriptor)
+	Merge(Aggregator, *Descriptor)
 }
 
-// MetricRecord is the unit of export, pairing a metric
+// Record is the unit of export, pairing a metric
 // instrument and set of labels.
-type MetricRecord interface {
+type Record interface {
 	// Descriptor() describes the metric instrument.
 	Descriptor() *Descriptor
 
@@ -49,19 +72,19 @@ type MetricRecord interface {
 	Labels() []core.KeyValue
 }
 
-// MetricKind describes the kind of instrument.
-type MetricKind int8
+// Kind describes the kind of instrument.
+type Kind int8
 
 const (
-	CounterMetricKind MetricKind = iota
-	GaugeMetricKind
-	MeasureMetricKind
+	CounterKind Kind = iota
+	GaugeKind
+	MeasureKind
 )
 
 // Descriptor describes a metric instrument to the exporter.
 type Descriptor struct {
 	name        string
-	metricKind  MetricKind
+	metricKind  Kind
 	keys        []core.Key
 	description string
 	unit        unit.Unit
@@ -70,10 +93,10 @@ type Descriptor struct {
 }
 
 // NewDescriptor builds a new descriptor, for use by `Meter`
-// implementations.
+// implementations to interface with a metric export pipeline.
 func NewDescriptor(
 	name string,
-	metricKind MetricKind,
+	metricKind Kind,
 	keys []core.Key,
 	description string,
 	unit unit.Unit,
@@ -95,7 +118,7 @@ func (d *Descriptor) Name() string {
 	return d.name
 }
 
-func (d *Descriptor) MetricKind() MetricKind {
+func (d *Descriptor) MetricKind() Kind {
 	return d.metricKind
 }
 

sdk/export/span.go → sdk/export/trace/trace.go

@@ -12,9 +12,10 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package export
+package trace // import "go.opentelemetry.io/otel/sdk/export/trace"
 
 import (
+	"context"
 	"time"
 
 	"google.golang.org/grpc/codes"
@@ -23,6 +24,27 @@ import (
 	apitrace "go.opentelemetry.io/otel/api/trace"
 )
 
+// SpanSyncer is a type for functions that receive a single sampled trace span.
+//
+// The ExportSpan method is called synchronously. Therefore, it should not take
+// forever to process the span.
+//
+// The SpanData should not be modified.
+type SpanSyncer interface {
+	ExportSpan(context.Context, *SpanData)
+}
+
+// SpanBatcher is a type for functions that receive batched of sampled trace
+// spans.
+//
+// The ExportSpans method is called asynchronously. However its should not take
+// forever to process the spans.
+//
+// The SpanData should not be modified.
+type SpanBatcher interface {
+	ExportSpans(context.Context, []*SpanData)
+}
+
 // SpanData contains all the information collected by a span.
 type SpanData struct {
 	SpanContext  core.SpanContext

sdk/metric/aggregator/array/array.go

@@ -22,7 +22,7 @@ import (
 	"unsafe"
 
 	"go.opentelemetry.io/otel/api/core"
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/metric"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator"
 )
 
@@ -37,7 +37,7 @@ type (
 	Points []core.Number
 )
 
-var _ export.MetricAggregator = &Aggregator{}
+var _ export.Aggregator = &Aggregator{}
 
 func New() *Aggregator {
 	return &Aggregator{}
@@ -68,7 +68,7 @@ func (c *Aggregator) Quantile(q float64) (core.Number, error) {
 	return c.checkpoint.Quantile(q)
 }
 
-func (c *Aggregator) Collect(ctx context.Context, rec export.MetricRecord, exp export.MetricBatcher) {
+func (c *Aggregator) Collect(ctx context.Context, rec export.Record, exp export.Batcher) {
 	c.lock.Lock()
 	c.checkpoint, c.current = c.current, nil
 	c.lock.Unlock()
@@ -87,7 +87,7 @@ func (c *Aggregator) Collect(ctx context.Context, rec export.MetricRecord, exp e
 	exp.Export(ctx, rec, c)
 }
 
-func (c *Aggregator) Update(_ context.Context, number core.Number, rec export.MetricRecord) {
+func (c *Aggregator) Update(_ context.Context, number core.Number, rec export.Record) {
 	desc := rec.Descriptor()
 	kind := desc.NumberKind()
 
@@ -107,7 +107,7 @@ func (c *Aggregator) Update(_ context.Context, number core.Number, rec export.Me
 	c.lock.Unlock()
 }
 
-func (c *Aggregator) Merge(oa export.MetricAggregator, desc *export.Descriptor) {
+func (c *Aggregator) Merge(oa export.Aggregator, desc *export.Descriptor) {
 	o, _ := oa.(*Aggregator)
 	if o == nil {
 		// TODO warn

sdk/metric/aggregator/array/array_test.go

@@ -23,7 +23,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/otel/api/core"
-	"go.opentelemetry.io/otel/sdk/export"
+	export "go.opentelemetry.io/otel/sdk/export/metric"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator"
 	"go.opentelemetry.io/otel/sdk/metric/aggregator/test"
 )
@@ -36,7 +36,7 @@ type updateTest struct {
 func (ut *updateTest) run(t *testing.T, profile test.Profile) {
 	ctx := context.Background()
 
-	batcher, record := test.NewAggregatorTest(export.MeasureMetricKind, profile.NumberKind, !ut.absolute)
+	batcher, record := test.NewAggregatorTest(export.MeasureKind, profile.NumberKind, !ut.absolute)
 
 	agg := New()
 
@@ -106,7 +106,7 @@ type mergeTest struct {
 func (mt *mergeTest) run(t *testing.T, profile test.Profile) {
 	ctx := context.Background()
 
-	batcher, record := test.NewAggregatorTest(export.MeasureMetricKind, profile.NumberKind, !mt.absolute)
+	batcher, record := test.NewAggregatorTest(export.MeasureKind, profile.NumberKind, !mt.absolute)
 
 	agg1 := New()
 	agg2 := New()
@@ -198,7 +198,7 @@ func TestArrayErrors(t *testing.T) {
 
 		ctx := context.Background()
 
-		batcher, record := test.NewAggregatorTest(export.MeasureMetricKind, profile.NumberKind, false)
+		batcher, record := test.NewAggregatorTest(export.MeasureKind, profile.NumberKind, false)
 
 		agg.Update(ctx, core.Number(0), record)
 
@@ -226,7 +226,7 @@ func TestArrayErrors(t *testing.T) {
 func TestArrayFloat64(t *testing.T) {
 	for _, absolute := range []bool{false, true} {
 		t.Run(fmt.Sprint("Absolute=", absolute), func(t *testing.T) {
-			batcher, record := test.NewAggregatorTest(export.MeasureMetricKind, core.Float64NumberKind, !absolute)
+			batcher, record := test.NewAggregatorTest(export.MeasureKind, core.Float64NumberKind, !absolute)
 
 			fpsf := func(sign int) []float64 {
 				// Check behavior of a bunch of odd floating