Restore the experimental/streaming SDK implementation (#55)

* Fix streaming - part 1

* Eliminate span{} state

* Eliminate trace/ dir

* Avoid missing AddEvent helpers

example/basic/main.go

@@ -23,7 +23,6 @@ import (
 	"go.opentelemetry.io/api/stats"
 	"go.opentelemetry.io/api/tag"
 	"go.opentelemetry.io/api/trace"
-	"go.opentelemetry.io/experimental/streaming/sdk/event"
 )
 
 var (
@@ -64,7 +63,7 @@ func main() {
 
 	err := tracer.WithSpan(ctx, "operation", func(ctx context.Context) error {
 
-		trace.CurrentSpan(ctx).AddEvent(ctx, event.WithAttr("Nice operation!", key.New("bogons").Int(100)))
+		trace.CurrentSpan(ctx).Event(ctx, "Nice operation!", key.New("bogons").Int(100))
 
 		trace.CurrentSpan(ctx).SetAttributes(anotherKey.String("yes"))
 
@@ -76,7 +75,7 @@ func main() {
 			func(ctx context.Context) error {
 				trace.CurrentSpan(ctx).SetAttribute(lemonsKey.String("five"))
 
-				trace.CurrentSpan(ctx).AddEvent(ctx, event.WithString("Format schmormat %d!", 100))
+				trace.CurrentSpan(ctx).Event(ctx, "Sub span event")
 
 				stats.Record(ctx, measureTwo.M(1.3))
 

experimental/streaming/exporter/observer/observer.go

@@ -150,7 +150,14 @@ func Foreach(f func(Observer)) {
 	}
 }
 
-func NewScope(parent ScopeID, kv ...core.KeyValue) ScopeID {
-	// TODO
-	return parent
+func NewScope(parent ScopeID, attributes ...core.KeyValue) ScopeID {
+	eventID := Record(Event{
+		Type:       NEW_SCOPE,
+		Scope:      parent,
+		Attributes: attributes,
+	})
+	return ScopeID{
+		EventID:     eventID,
+		SpanContext: parent.SpanContext,
+	}
 }

experimental/streaming/exporter/reader/format/format.go

@@ -21,7 +21,9 @@ import (
 	"go.opentelemetry.io/api/core"
 	"go.opentelemetry.io/api/key"
 	"go.opentelemetry.io/experimental/streaming/exporter/reader"
-	"go.opentelemetry.io/experimental/streaming/sdk/trace"
+
+	// TODO this should not be an SDK dependency; move conventional tags into the API.
+	"go.opentelemetry.io/experimental/streaming/sdk"
 )
 
 var (
@@ -119,10 +121,10 @@ func AppendEvent(buf *strings.Builder, data reader.Event) {
 		data.Tags.Foreach(f(true))
 	}
 	if data.SpanContext.HasSpanID() {
-		f(false)(trace.SpanIDKey.String(data.SpanContext.SpanIDString()))
+		f(false)(sdk.SpanIDKey.String(data.SpanContext.SpanIDString()))
 	}
 	if data.SpanContext.HasTraceID() {
-		f(false)(trace.TraceIDKey.String(data.SpanContext.TraceIDString()))
+		f(false)(sdk.TraceIDKey.String(data.SpanContext.TraceIDString()))
 	}
 
 	buf.WriteString(" ]\n")

experimental/streaming/exporter/reader/reader.go

@@ -117,6 +117,11 @@ func NewReaderObserver(readers ...Reader) observer.Observer {
 }
 
 func (ro *readerObserver) Observe(event observer.Event) {
+	// TODO this should check for out-of-order events and buffer.
+	ro.orderedObserve(event)
+}
+
+func (ro *readerObserver) orderedObserve(event observer.Event) {
 	read := Event{
 		Time:       event.Time,
 		Sequence:   event.Sequence,
@@ -169,7 +174,7 @@ func (ro *readerObserver) Observe(event observer.Event) {
 	case observer.FINISH_SPAN:
 		attrs, span := ro.readScope(event.Scope)
 		if span == nil {
-			panic("span not found")
+			panic(fmt.Sprint("span not found", event.Scope))
 		}
 
 		read.Name = span.name

experimental/streaming/exporter/spanlog/spanlog.go

@@ -18,7 +18,6 @@ import (
 	"os"
 	"strings"
 
-	"go.opentelemetry.io/experimental/streaming/exporter/buffer"
 	"go.opentelemetry.io/experimental/streaming/exporter/observer"
 	"go.opentelemetry.io/experimental/streaming/exporter/spandata"
 	"go.opentelemetry.io/experimental/streaming/exporter/spandata/format"
@@ -27,7 +26,7 @@ import (
 type spanLog struct{}
 
 func New() observer.Observer {
-	return buffer.NewBuffer(1000, spandata.NewReaderObserver(&spanLog{}))
+	return spandata.NewReaderObserver(&spanLog{})
 }
 
 func (s *spanLog) Read(data *spandata.Span) {

experimental/streaming/sdk/package.go

@@ -0,0 +1,9 @@
+package sdk
+
+import (
+	"go.opentelemetry.io/api/trace"
+)
+
+func init() {
+	trace.SetGlobalTracer(New())
+}

experimental/streaming/sdk/trace/span.go → experimental/streaming/sdk/span.go

@@ -12,11 +12,10 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package trace
+package sdk
 
 import (
 	"context"
-	"sync"
 
 	"google.golang.org/grpc/codes"
 
@@ -28,22 +27,14 @@ import (
 )
 
 type span struct {
-	tracer      *tracer
-	spanContext core.SpanContext
-	lock        sync.Mutex
-	eventID     observer.EventID
-	finishOnce  sync.Once
-	recordEvent bool
-	status      codes.Code
+	tracer  *tracer
+	initial observer.ScopeID
 }
 
 // SpancContext returns span context of the span. Return SpanContext is usable
 // even after the span is finished.
 func (sp *span) SpanContext() core.SpanContext {
-	if sp == nil {
-		return core.INVALID_SPAN_CONTEXT
-	}
-	return sp.spanContext
+	return sp.initial.SpanContext
 }
 
 // IsRecordingEvents returns true is the span is active and recording events is enabled.
@@ -53,122 +44,55 @@ func (sp *span) IsRecordingEvents() bool {
 
 // SetStatus sets the status of the span.
 func (sp *span) SetStatus(status codes.Code) {
-	if sp == nil {
-		return
-	}
-	sid := sp.ScopeID()
-
 	observer.Record(observer.Event{
-		Type:     observer.SET_STATUS,
-		Scope:    sid,
-		Sequence: sid.EventID,
-		Status:   status,
+		Type:   observer.SET_STATUS,
+		Scope:  sp.ScopeID(),
+		Status: status,
 	})
-	sp.status = status
 }
 
 func (sp *span) ScopeID() observer.ScopeID {
-	if sp == nil {
-		return observer.ScopeID{}
-	}
-	sp.lock.Lock()
-	sid := observer.ScopeID{
-		EventID:     sp.eventID,
-		SpanContext: sp.spanContext,
-	}
-	sp.lock.Unlock()
-	return sid
-}
-
-func (sp *span) updateScope() (observer.ScopeID, observer.EventID) {
-	next := observer.NextEventID()
-
-	sp.lock.Lock()
-	sid := observer.ScopeID{
-		EventID:     sp.eventID,
-		SpanContext: sp.spanContext,
-	}
-	sp.eventID = next
-	sp.lock.Unlock()
-
-	return sid, next
-}
-
-func (sp *span) SetError(v bool) {
-	sp.SetAttribute(ErrorKey.Bool(v))
+	return sp.initial
 }
 
 func (sp *span) SetAttribute(attribute core.KeyValue) {
-	if sp == nil {
-		return
-	}
-
-	sid, next := sp.updateScope()
-
 	observer.Record(observer.Event{
 		Type:      observer.MODIFY_ATTR,
-		Scope:     sid,
-		Sequence:  next,
+		Scope:     sp.ScopeID(),
 		Attribute: attribute,
 	})
 }
 
 func (sp *span) SetAttributes(attributes ...core.KeyValue) {
-	if sp == nil {
-		return
-	}
-
-	sid, next := sp.updateScope()
-
 	observer.Record(observer.Event{
 		Type:       observer.MODIFY_ATTR,
-		Scope:      sid,
-		Sequence:   next,
+		Scope:      sp.ScopeID(),
 		Attributes: attributes,
 	})
 }
 
 func (sp *span) ModifyAttribute(mutator tag.Mutator) {
-	if sp == nil {
-		return
-	}
-
-	sid, next := sp.updateScope()
-
 	observer.Record(observer.Event{
-		Type:     observer.MODIFY_ATTR,
-		Scope:    sid,
-		Sequence: next,
-		Mutator:  mutator,
+		Type:    observer.MODIFY_ATTR,
+		Scope:   sp.ScopeID(),
+		Mutator: mutator,
 	})
 }
 
 func (sp *span) ModifyAttributes(mutators ...tag.Mutator) {
-	if sp == nil {
-		return
-	}
-
-	sid, next := sp.updateScope()
-
 	observer.Record(observer.Event{
 		Type:     observer.MODIFY_ATTR,
-		Scope:    sid,
-		Sequence: next,
+		Scope:    sp.ScopeID(),
 		Mutators: mutators,
 	})
 }
 
 func (sp *span) Finish() {
-	if sp == nil {
-		return
-	}
 	recovered := recover()
-	sp.finishOnce.Do(func() {
-		observer.Record(observer.Event{
-			Type:      observer.FINISH_SPAN,
-			Scope:     sp.ScopeID(),
-			Recovered: recovered,
-		})
+	observer.Record(observer.Event{
+		Type:      observer.FINISH_SPAN,
+		Scope:     sp.ScopeID(),
+		Recovered: recovered,
 	})
 	if recovered != nil {
 		panic(recovered)