rename Log and Logf interface to AddEvent and AddEventf.

api/event/event.go

@@ -0,0 +1,59 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package event
+
+import (
+	"fmt"
+
+	"github.com/open-telemetry/opentelemetry-go/api/core"
+)
+
+type (
+	event struct {
+		message    string
+		attributes []core.KeyValue
+	}
+
+	// Event interface provides methods to retrieve Event properties.
+	Event interface {
+
+		// Message interface retrieves message string of the Event.
+		Message() string
+
+		// Attributes interface returns a copy of attributes associated with the Event.
+		Attributes() []core.KeyValue
+	}
+)
+
+var _ Event = (*event)(nil)
+
+// WithAttr creates an Event with Attributes and a message.
+// Attributes are immutable.
+func WithAttr(msg string, attributes ...core.KeyValue) Event {
+	return event{message: msg, attributes: attributes}
+}
+
+// WithString creates an Event with formatted string.
+func WithString(f string, args ...interface{}) Event {
+	return event{message: fmt.Sprint(f, args), attributes: nil}
+}
+
+func (e event) Message() string {
+	return e.message
+}
+
+func (e event) Attributes() []core.KeyValue {
+	return append(e.attributes[:0:0], e.attributes...)
+}

api/trace/api.go

@@ -21,7 +21,7 @@ import (
 	"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/event"
 	"github.com/open-telemetry/opentelemetry-go/api/scope"
 	"github.com/open-telemetry/opentelemetry-go/api/stats"
 	"github.com/open-telemetry/opentelemetry-go/api/tag"
@@ -51,8 +51,6 @@ type (
 	Span interface {
 		scope.Mutable
 
-		log.Interface
-
 		stats.Interface
 
 		SetError(bool)
@@ -61,6 +59,9 @@ type (
 
 		Finish()
 
+		// AddEvent adds an event to the span.
+		AddEvent(ctx context.Context, event event.Event)
+
 		// IsRecordingEvents returns true is the span is active and recording events is enabled.
 		IsRecordingEvents() bool
 

api/trace/span.go

@@ -20,7 +20,7 @@ import (
 	"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/event"
 	"github.com/open-telemetry/opentelemetry-go/api/stats"
 	"github.com/open-telemetry/opentelemetry-go/exporter/observer"
 )
@@ -167,12 +167,13 @@ func (sp *span) Tracer() Tracer {
 	return sp.tracer
 }
 
-func (sp *span) Log(ctx context.Context, msg string, args ...core.KeyValue) {
-	log.With(sp).Log(ctx, msg, args...)
-}
+func (sp *span) AddEvent(ctx context.Context, event event.Event) {
 
-func (sp *span) Logf(ctx context.Context, fmt string, args ...interface{}) {
-	log.With(sp).Logf(ctx, fmt, args...)
+	observer.Record(observer.Event{
+		Type:    observer.ADD_EVENT,
+		Event:   event,
+		Context: ctx,
+	})
 }
 
 func (sp *span) Record(ctx context.Context, m ...core.Measurement) {

api/trace/trace.go

@@ -23,7 +23,7 @@ import (
 	"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/event"
 	"github.com/open-telemetry/opentelemetry-go/api/scope"
 	"github.com/open-telemetry/opentelemetry-go/api/tag"
 	"github.com/open-telemetry/opentelemetry-go/exporter/observer"
@@ -90,7 +90,7 @@ func (t *tracer) WithSpan(ctx context.Context, name string, body func(context.Co
 
 	if err := body(ctx); err != nil {
 		span.SetAttribute(ErrorKey.Bool(true))
-		log.Log(ctx, "span error", MessageKey.String(err.Error()))
+		span.AddEvent(ctx, event.WithAttr("span error", MessageKey.String(err.Error())))
 		return err
 	}
 	return nil

example/example.go

@@ -17,12 +17,12 @@ package main
 import (
 	"context"
 
-	"github.com/open-telemetry/opentelemetry-go/api/log"
 	"github.com/open-telemetry/opentelemetry-go/api/metric"
 	"github.com/open-telemetry/opentelemetry-go/api/stats"
 	"github.com/open-telemetry/opentelemetry-go/api/tag"
 	"github.com/open-telemetry/opentelemetry-go/api/trace"
 
+	"github.com/open-telemetry/opentelemetry-go/api/event"
 	"github.com/open-telemetry/opentelemetry-go/exporter/loader"
 )
 
@@ -64,7 +64,7 @@ func main() {
 
 		trace.SetError(ctx, true)
 
-		log.Log(ctx, "Nice operation!", tag.New("bogons").Int(100))
+		trace.Active(ctx).AddEvent(ctx, event.WithAttr("Nice operation!", tag.New("bogons").Int(100)))
 
 		trace.Active(ctx).SetAttributes(anotherKey.String("yes"))
 
@@ -76,7 +76,7 @@ func main() {
 			func(ctx context.Context) error {
 				trace.Active(ctx).SetAttribute(lemonsKey.String("five"))
 
-				log.Logf(ctx, "Format schmormat %d!", 100)
+				trace.Active(ctx).AddEvent(ctx, event.WithString("Format schmormat %d!", 100))
 
 				stats.Record(ctx, measureTwo.M(1.3))
 

example/http/server/server.go

@@ -19,11 +19,11 @@ import (
 	"net/http"
 
 	"github.com/open-telemetry/opentelemetry-go/api/core"
-	"github.com/open-telemetry/opentelemetry-go/api/log"
 	"github.com/open-telemetry/opentelemetry-go/api/tag"
 	"github.com/open-telemetry/opentelemetry-go/api/trace"
 	"github.com/open-telemetry/opentelemetry-go/plugin/httptrace"
 
+	"github.com/open-telemetry/opentelemetry-go/api/event"
 	_ "github.com/open-telemetry/opentelemetry-go/exporter/loader"
 )
 
@@ -50,7 +50,7 @@ func main() {
 		)
 		defer span.Finish()
 
-		log.Log(ctx, "handling this...")
+		span.AddEvent(ctx, event.WithString("handling this..."))
 
 		io.WriteString(w, "Hello, world!\n")
 	}

exporter/observer/observer.go

@@ -23,11 +23,13 @@ import (
 	"google.golang.org/grpc/codes"
 
 	"github.com/open-telemetry/opentelemetry-go/api/core"
+	"github.com/open-telemetry/opentelemetry-go/api/event"
 )
 
 type (
 	EventType int
 
+	// TODO: this Event is confusing with event.Event.
 	Event struct {
 		// Automatic fields
 		Sequence core.EventID // Auto-filled
@@ -40,10 +42,10 @@ type (
 
 		// Arguments (type-specific)
 		Attribute  core.KeyValue   // SET_ATTRIBUTE
-		Attributes []core.KeyValue // SET_ATTRIBUTES, LOG_EVENT
+		Attributes []core.KeyValue // SET_ATTRIBUTES
 		Mutator    core.Mutator    // SET_ATTRIBUTE
 		Mutators   []core.Mutator  // SET_ATTRIBUTES
-		Arguments  []interface{}   // LOGF_EVENT
+		Event      event.Event     // ADD_EVENT
 		Recovered  interface{}     // FINISH_SPAN
 		Status     codes.Code      // SET_STATUS
 
@@ -68,8 +70,8 @@ const (
 	INVALID EventType = iota
 	START_SPAN
 	FINISH_SPAN
-	LOG_EVENT
-	LOGF_EVENT
+	ADD_EVENT
+	ADD_EVENTF
 	NEW_SCOPE
 	NEW_MEASURE
 	NEW_METRIC

exporter/reader/format/format.go

@@ -64,11 +64,14 @@ func AppendEvent(buf *strings.Builder, data reader.Event) {
 		buf.WriteString(data.Duration.String())
 		buf.WriteString(")")
 
-	case reader.LOG_EVENT:
-		buf.WriteString(data.Message)
-
-	case reader.LOGF_EVENT:
-		buf.WriteString(data.Message)
+	case reader.ADD_EVENT:
+		buf.WriteString("event: ")
+		buf.WriteString(data.Event.Message())
+		buf.WriteString(" (")
+		for _, kv := range data.Event.Attributes() {
+			buf.WriteString(" " + kv.Key.Name() + "=" + kv.Value.Emit())
+		}
+		buf.WriteString(")")
 
 	case reader.MODIFY_ATTR:
 		buf.WriteString("modify attr")

exporter/reader/reader.go

@@ -22,6 +22,7 @@ import (
 	"google.golang.org/grpc/codes"
 
 	"github.com/open-telemetry/opentelemetry-go/api/core"
+	"github.com/open-telemetry/opentelemetry-go/api/event"
 	"github.com/open-telemetry/opentelemetry-go/api/metric"
 	"github.com/open-telemetry/opentelemetry-go/api/tag"
 	"github.com/open-telemetry/opentelemetry-go/api/trace"
@@ -43,6 +44,7 @@ type (
 		SpanContext core.SpanContext
 		Tags        tag.Map
 		Attributes  tag.Map
+		Event       event.Event
 		Stats       []Measurement
 
 		Parent           core.SpanContext
@@ -106,8 +108,7 @@ const (
 	INVALID EventType = iota
 	START_SPAN
 	FINISH_SPAN
-	LOG_EVENT
-	LOGF_EVENT
+	ADD_EVENT
 	MODIFY_ATTR
 	RECORD_STATS
 	SET_STATUS
@@ -260,28 +261,16 @@ func (ro *readerObserver) Observe(event observer.Event) {
 		ro.metrics.Store(event.Sequence, metric)
 		return
 
-	case observer.LOG_EVENT:
-		read.Type = LOG_EVENT
-
-		read.Message = event.String
+	case observer.ADD_EVENT:
+		read.Type = ADD_EVENT
+		read.Event = event.Event
 
 		attrs, span := ro.readScope(event.Scope)
 		read.Attributes = attrs.Apply(core.KeyValue{}, event.Attributes, core.Mutator{}, nil)
 		if span != nil {
 			read.SpanContext = span.spanContext
 		}
 
-	case observer.LOGF_EVENT:
-		// TODO: this can't be done lazily, must be done before Record()
-		read.Message = fmt.Sprintf(event.String, event.Arguments...)
-
-		read.Type = LOGF_EVENT
-		attrs, span := ro.readScope(event.Scope)
-		read.Attributes = attrs
-		if span != nil {
-			read.SpanContext = span.spanContext
-		}
-
 	case observer.RECORD_STATS:
 		read.Type = RECORD_STATS