Add SetStatus, SpanContext and IsRecordingEvent (#12)

* Add span apis.
- SetStatus
- SpanContext
- IsRecordingEvent

* fix formatting.

* use grpc/codes.Code

* change Option to SpanOption

* fix format errors.

api/trace/api.go

@@ -18,6 +18,8 @@ import (
 	"context"
 	"time"
 
+	"google.golang.org/grpc/codes"
+
 	"github.com/open-telemetry/opentelemetry-go/api/core"
 	"github.com/open-telemetry/opentelemetry-go/api/log"
 	"github.com/open-telemetry/opentelemetry-go/api/scope"
@@ -27,7 +29,7 @@ import (
 
 type (
 	Tracer interface {
-		Start(context.Context, string, ...Option) (context.Context, Span)
+		Start(context.Context, string, ...SpanOption) (context.Context, Span)
 
 		WithSpan(
 			ctx context.Context,
@@ -58,17 +60,29 @@ type (
 		Tracer() Tracer
 
 		Finish()
+
+		// IsRecordingEvents returns true is the span is active and recording events is enabled.
+		IsRecordingEvents() bool
+
+		// SpancContext returns span context of the span. Return SpanContext is usable
+		// even after the span is finished.
+		SpanContext() core.SpanContext
+
+		SetStatus(codes.Code)
 	}
 
 	Injector interface {
 		Inject(core.SpanContext, tag.Map)
 	}
 
-	Option struct {
-		attribute  core.KeyValue
-		attributes []core.KeyValue
-		startTime  time.Time
-		reference  Reference
+	// SpanOption apply changes to SpanOptions.
+	SpanOption func(*SpanOptions)
+
+	SpanOptions struct {
+		attributes  []core.KeyValue
+		startTime   time.Time
+		reference   Reference
+		recordEvent bool
 	}
 
 	Reference struct {
@@ -95,7 +109,7 @@ func SetGlobalTracer(t Tracer) {
 	global.Store(t)
 }
 
-func Start(ctx context.Context, name string, opts ...Option) (context.Context, Span) {
+func Start(ctx context.Context, name string, opts ...SpanOption) (context.Context, Span) {
 	return GlobalTracer().Start(ctx, name, opts...)
 }
 
@@ -121,38 +135,38 @@ func Inject(ctx context.Context, injector Injector) {
 	span.Tracer().Inject(ctx, span, injector)
 }
 
-func WithStartTime(t time.Time) Option {
-	return Option{
-		startTime: t,
+func WithStartTime(t time.Time) SpanOption {
+	return func(o *SpanOptions) {
+		o.startTime = t
 	}
 }
 
-func WithAttributes(attrs ...core.KeyValue) Option {
-	return Option{
-		attributes: attrs,
+func WithAttributes(attrs ...core.KeyValue) SpanOption {
+	return func(o *SpanOptions) {
+		o.attributes = attrs
 	}
 }
 
-func WithAttribute(attr core.KeyValue) Option {
-	return Option{
-		attribute: attr,
+func WithRecordEvents() SpanOption {
+	return func(o *SpanOptions) {
+		o.recordEvent = true
 	}
 }
 
-func ChildOf(sc core.SpanContext) Option {
-	return Option{
-		reference: Reference{
+func ChildOf(sc core.SpanContext) SpanOption {
+	return func(o *SpanOptions) {
+		o.reference = Reference{
 			SpanContext:      sc,
 			RelationshipType: ChildOfRelationship,
-		},
+		}
 	}
 }
 
-func FollowsFrom(sc core.SpanContext) Option {
-	return Option{
-		reference: Reference{
+func FollowsFrom(sc core.SpanContext) SpanOption {
+	return func(o *SpanOptions) {
+		o.reference = Reference{
 			SpanContext:      sc,
 			RelationshipType: FollowsFromRelationship,
-		},
+		}
 	}
 }

api/trace/span.go

@@ -17,12 +17,44 @@ package trace
 import (
 	"context"
 
+	"google.golang.org/grpc/codes"
+
 	"github.com/open-telemetry/opentelemetry-go/api/core"
 	"github.com/open-telemetry/opentelemetry-go/api/log"
 	"github.com/open-telemetry/opentelemetry-go/api/stats"
 	"github.com/open-telemetry/opentelemetry-go/exporter/observer"
 )
 
+// 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
+}
+
+// IsRecordingEvents returns true is the span is active and recording events is enabled.
+func (sp *span) IsRecordingEvents() bool {
+	return false
+}
+
+// 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,
+	})
+	sp.status = status
+}
+
 func (sp *span) ScopeID() core.ScopeID {
 	if sp == nil {
 		return core.ScopeID{}

api/trace/trace.go

@@ -19,7 +19,8 @@ import (
 	"math/rand"
 	"sync"
 	"sync/atomic"
-	"time"
+
+	"google.golang.org/grpc/codes"
 
 	"github.com/open-telemetry/opentelemetry-go/api/core"
 	"github.com/open-telemetry/opentelemetry-go/api/log"
@@ -35,6 +36,8 @@ type (
 		lock        sync.Mutex
 		eventID     core.EventID
 		finishOnce  sync.Once
+		recordEvent bool
+		status      codes.Code
 	}
 
 	tracer struct {
@@ -93,34 +96,21 @@ func (t *tracer) WithSpan(ctx context.Context, name string, body func(context.Co
 	return nil
 }
 
-func (t *tracer) Start(ctx context.Context, name string, opts ...Option) (context.Context, Span) {
+func (t *tracer) Start(ctx context.Context, name string, opts ...SpanOption) (context.Context, Span) {
 	var child core.SpanContext
 
 	child.SpanID = rand.Uint64()
 
-	var startTime time.Time
-	var attributes []core.KeyValue
-	var reference Reference
+	o := &SpanOptions{}
 
 	for _, opt := range opts {
-		if !opt.startTime.IsZero() {
-			startTime = opt.startTime
-		}
-		if len(opt.attributes) != 0 {
-			attributes = append(opt.attributes, attributes...)
-		}
-		if opt.attribute.Key != nil {
-			attributes = append(attributes, opt.attribute)
-		}
-		if opt.reference.HasTraceID() {
-			reference = opt.reference
-		}
+		opt(o)
 	}
 
 	var parentScope core.ScopeID
 
-	if reference.HasTraceID() {
-		parentScope = reference.Scope()
+	if o.reference.HasTraceID() {
+		parentScope = o.reference.Scope()
 	} else {
 		parentScope = Active(ctx).ScopeID()
 	}
@@ -142,10 +132,11 @@ func (t *tracer) Start(ctx context.Context, name string, opts ...Option) (contex
 	span := &span{
 		spanContext: child,
 		tracer:      t,
+		recordEvent: o.recordEvent,
 		eventID: observer.Record(observer.Event{
-			Time:    startTime,
+			Time:    o.startTime,
 			Type:    observer.START_SPAN,
-			Scope:   scope.New(childScope, attributes...).ScopeID(),
+			Scope:   scope.New(childScope, o.attributes...).ScopeID(),
 			Context: ctx,
 			Parent:  parentScope,
 			String:  name,