internal/telemetry: moving towards a unified event based exporter

This adds a type to events and makes the logging calls use it.

Change-Id: Iaa50fe2e332caae611b1e00424c878a3bc479feb
Reviewed-on: https://go-review.googlesource.com/c/tools/+/221741
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

internal/lsp/debug/serve.go

@@ -570,18 +570,19 @@ func (e *exporter) FinishSpan(ctx context.Context, spn *telemetry.Span) {
 	}
 }
 
-func (e *exporter) Log(ctx context.Context, event telemetry.Event) {
+func (e *exporter) ProcessEvent(ctx context.Context, event telemetry.Event) context.Context {
 	i := GetInstance(ctx)
-	if event.Error != nil || i == nil {
+	if event.Type == telemetry.EventLog && (event.Error != nil || i == nil) {
 		fmt.Fprintf(e.stderr, "%v\n", event)
 	}
-	if i == nil {
-		return
-	}
 	protocol.LogEvent(ctx, event)
-	if i.ocagent != nil {
-		i.ocagent.Log(ctx, event)
+	if i == nil {
+		return ctx
 	}
+	if i.ocagent != nil {
+		ctx = i.ocagent.ProcessEvent(ctx, event)
+	}
+	return ctx
 }
 
 func (e *exporter) Metric(ctx context.Context, data telemetry.MetricData) {

internal/lsp/protocol/context.go

@@ -18,14 +18,18 @@ func WithClient(ctx context.Context, client Client) context.Context {
 	return context.WithValue(ctx, clientKey, client)
 }
 
-func LogEvent(ctx context.Context, event telemetry.Event) {
+func LogEvent(ctx context.Context, event telemetry.Event) context.Context {
+	if event.Type != telemetry.EventLog {
+		return ctx
+	}
 	client, ok := ctx.Value(clientKey).(Client)
 	if !ok {
-		return
+		return ctx
 	}
 	msg := &LogMessageParams{Type: Info, Message: fmt.Sprint(event)}
 	if event.Error != nil {
 		msg.Type = Error
 	}
 	go client.LogMessage(xcontext.Detach(ctx), msg)
+	return ctx
 }

internal/telemetry/event.go

@@ -9,7 +9,14 @@ import (
 	"time"
 )
 
+type EventType uint8
+
+const (
+	EventLog = EventType(iota)
+)
+
 type Event struct {
+	Type    EventType
 	At      time.Time
 	Message string
 	Error   error

internal/telemetry/export/export.go

@@ -18,14 +18,14 @@ import (
 )
 
 type Exporter interface {
+	// ProcessEvent is a function that handles all events.
+	// Exporters may use information in the context to decide what to do with a
+	// given event.
+	ProcessEvent(context.Context, telemetry.Event) context.Context
+
 	StartSpan(context.Context, *telemetry.Span)
 	FinishSpan(context.Context, *telemetry.Span)
 
-	// Log is a function that handles logging events.
-	// Observers may use information in the context to decide what to do with a
-	// given log event.
-	Log(context.Context, telemetry.Event)
-
 	Metric(context.Context, telemetry.MetricData)
 }
 
@@ -85,18 +85,18 @@ func Tag(ctx context.Context, at time.Time, tags telemetry.TagList) {
 	})
 }
 
-func Log(ctx context.Context, event telemetry.Event) {
+func ProcessEvent(ctx context.Context, event telemetry.Event) context.Context {
 	exporterPtr := (*Exporter)(atomic.LoadPointer(&exporter))
 	if exporterPtr == nil {
-		return
+		return ctx
 	}
 	// If context has a span we need to add the event to it
 	span := telemetry.GetSpan(ctx)
 	if span != nil {
 		span.Events = append(span.Events, event)
 	}
-	// and now also hand the event of to the current observer
-	(*exporterPtr).Log(ctx, event)
+	// and now also hand the event of to the current exporter
+	return (*exporterPtr).ProcessEvent(ctx, event)
 }
 
 func Metric(ctx context.Context, data telemetry.MetricData) {

internal/telemetry/export/log.go

@@ -27,10 +27,11 @@ type logWriter struct {
 
 func (w *logWriter) StartSpan(context.Context, *telemetry.Span)  {}
 func (w *logWriter) FinishSpan(context.Context, *telemetry.Span) {}
-func (w *logWriter) Log(ctx context.Context, event telemetry.Event) {
+func (w *logWriter) ProcessEvent(ctx context.Context, event telemetry.Event) context.Context {
 	if w.onlyErrors && event.Error == nil {
-		return
+		return ctx
 	}
 	fmt.Fprintf(w.writer, "%v\n", event)
+	return ctx
 }
 func (w *logWriter) Metric(context.Context, telemetry.MetricData) {}

internal/telemetry/export/ocagent/ocagent.go

@@ -92,7 +92,9 @@ func (e *Exporter) FinishSpan(ctx context.Context, span *telemetry.Span) {
 	e.spans = append(e.spans, span)
 }
 
-func (e *Exporter) Log(context.Context, telemetry.Event) {}
+func (e *Exporter) ProcessEvent(ctx context.Context, event telemetry.Event) context.Context {
+	return ctx
+}
 
 func (e *Exporter) Metric(ctx context.Context, data telemetry.MetricData) {
 	e.mu.Lock()

internal/telemetry/log/log.go

@@ -18,7 +18,8 @@ type Event telemetry.Event
 
 // With sends a tag list to the installed loggers.
 func With(ctx context.Context, tags ...telemetry.Tag) {
-	export.Log(ctx, telemetry.Event{
+	export.ProcessEvent(ctx, telemetry.Event{
+		Type: telemetry.EventLog,
 		At:   time.Now(),
 		Tags: tags,
 	})
@@ -27,7 +28,8 @@ func With(ctx context.Context, tags ...telemetry.Tag) {
 // Print takes a message and a tag list and combines them into a single tag
 // list before delivering them to the loggers.
 func Print(ctx context.Context, message string, tags ...telemetry.Tag) {
-	export.Log(ctx, telemetry.Event{
+	export.ProcessEvent(ctx, telemetry.Event{
+		Type:    telemetry.EventLog,
 		At:      time.Now(),
 		Message: message,
 		Tags:    tags,
@@ -42,7 +44,8 @@ func Error(ctx context.Context, message string, err error, tags ...telemetry.Tag
 		err = errorString(message)
 		message = ""
 	}
-	export.Log(ctx, telemetry.Event{
+	export.ProcessEvent(ctx, telemetry.Event{
+		Type:    telemetry.EventLog,
 		At:      time.Now(),
 		Message: message,
 		Error:   err,