Zipkin-specific observer support

closes #156

observer.go

@@ -0,0 +1,53 @@
+package zipkintracer
+
+import (
+	"time"
+
+	"github.com/openzipkin/zipkin-go"
+	"github.com/openzipkin/zipkin-go/model"
+)
+
+// ZipkinStartSpanOptions allows ZipkinObserver.OnStartSpan() to inspect
+// options used during zipkin.Span creation
+type ZipkinStartSpanOptions struct {
+	// Parent span context reference, if any
+	Parent *model.SpanContext
+
+	// Span's start time
+	StartTime time.Time
+
+	// Kind clarifies context of timestamp, duration and remoteEndpoint in a span.
+	Kind model.Kind
+
+	// Tags used during span creation
+	Tags map[string]string
+
+	// RemoteEndpoint used during span creation
+	RemoteEndpoint *model.Endpoint
+}
+
+// ZipkinObserver may be registered with a Tracer to receive notifications about new Spans
+type ZipkinObserver interface {
+	// OnStartSpan is called when new Span is created. Creates and returns span observer.
+	// If the observer is not interested in the given span, it must return nil.
+	OnStartSpan(sp zipkin.Span, operationName string, options *ZipkinStartSpanOptions) ZipkinSpanObserver
+}
+
+// ZipkinSpanObserver is created by the ZipkinObserver and receives notifications about
+// other Span events.
+type ZipkinSpanObserver interface {
+	// Callback called from zipkin.Span.SetName()
+	OnSetName(operationName string)
+
+	// Callback called from zipkin.Span.SetTag()
+	OnSetTag(key, value string)
+
+	// Callback called from zipkin.Span.Annotate()
+	OnAnnotate(t time.Time, annotation string)
+
+	// Callback called from zipkin.Span.FinishedWithDuration()
+	OnFinishedWithDuration(duration time.Duration)
+
+	// Callback called from zipkin.Span.Finish()
+	OnFinish()
+}

span.go

@@ -31,17 +31,22 @@ type FinisherWithDuration interface {
 }
 
 type spanImpl struct {
-	tracer     *tracerImpl
-	zipkinSpan zipkin.Span
-	startTime  time.Time
-	observer   otobserver.SpanObserver
+	tracer         *tracerImpl
+	zipkinSpan     zipkin.Span
+	startTime      time.Time
+	observer       otobserver.SpanObserver
+	zipkinObserver ZipkinSpanObserver
 }
 
 func (s *spanImpl) SetOperationName(operationName string) opentracing.Span {
 	if s.observer != nil {
 		s.observer.OnSetOperationName(operationName)
 	}
 
+	if s.zipkinObserver != nil {
+		s.zipkinObserver.OnSetName(operationName)
+	}
+
 	s.zipkinSpan.SetName(operationName)
 	return s
 }
@@ -67,7 +72,13 @@ func (s *spanImpl) SetTag(key string, value interface{}) opentracing.Span {
 		return s
 	}
 
-	s.zipkinSpan.Tag(key, fmt.Sprint(value))
+	tagValue := fmt.Sprint(value)
+
+	if s.zipkinObserver != nil {
+		s.zipkinObserver.OnSetTag(key, tagValue)
+	}
+
+	s.zipkinSpan.Tag(key, tagValue)
 	return s
 }
 
@@ -78,7 +89,14 @@ func (s *spanImpl) LogKV(keyValues ...interface{}) {
 	}
 
 	for _, field := range fields {
-		s.zipkinSpan.Annotate(time.Now(), field.String())
+		t := time.Now()
+		fieldValue := field.String()
+
+		if s.zipkinObserver != nil {
+			s.zipkinObserver.OnAnnotate(t, fieldValue)
+		}
+
+		s.zipkinSpan.Annotate(t, fieldValue)
 	}
 }
 
@@ -88,7 +106,13 @@ func (s *spanImpl) LogFields(fields ...log.Field) {
 
 func (s *spanImpl) logFields(t time.Time, fields ...log.Field) {
 	for _, field := range fields {
-		s.zipkinSpan.Annotate(t, field.String())
+		annotation := field.String()
+
+		if s.zipkinObserver != nil {
+			s.zipkinObserver.OnAnnotate(t, annotation)
+		}
+
+		s.zipkinSpan.Annotate(t, annotation)
 	}
 }
 
@@ -110,14 +134,24 @@ func (s *spanImpl) Log(ld opentracing.LogData) {
 		ld.Timestamp = time.Now()
 	}
 
-	s.zipkinSpan.Annotate(ld.Timestamp, fmt.Sprintf("%s:%s", ld.Event, ld.Payload))
+	annotation := fmt.Sprintf("%s:%s", ld.Event, ld.Payload)
+
+	if s.zipkinObserver != nil {
+		s.zipkinObserver.OnAnnotate(ld.Timestamp, annotation)
+	}
+
+	s.zipkinSpan.Annotate(ld.Timestamp, annotation)
 }
 
 func (s *spanImpl) Finish() {
 	if s.observer != nil {
 		s.observer.OnFinish(opentracing.FinishOptions{})
 	}
 
+	if s.zipkinObserver != nil {
+		s.zipkinObserver.OnFinish()
+	}
+
 	s.zipkinSpan.Finish()
 }
 
@@ -135,10 +169,21 @@ func (s *spanImpl) FinishWithOptions(opts opentracing.FinishOptions) {
 		if !ok {
 			return
 		}
-		f.FinishedWithDuration(opts.FinishTime.Sub(s.startTime))
+
+		dur := opts.FinishTime.Sub(s.startTime)
+
+		if s.zipkinObserver != nil {
+			s.zipkinObserver.OnFinishedWithDuration(dur)
+		}
+
+		f.FinishedWithDuration(dur)
 		return
 	}
 
+	if s.zipkinObserver != nil {
+		s.zipkinObserver.OnFinish()
+	}
+
 	s.Finish()
 }
 

tracer.go

@@ -58,22 +58,25 @@ func (t *tracerImpl) StartSpan(operationName string, opts ...opentracing.StartSp
 
 	zopts := make([]zipkin.SpanOption, 0)
 
+	var zipkinStartSpanOptions ZipkinStartSpanOptions
+
 	// Parent
 	if len(startSpanOptions.References) > 0 {
 		parent, ok := (startSpanOptions.References[0].ReferencedContext).(SpanContext)
 		if ok {
 			zopts = append(zopts, zipkin.Parent(model.SpanContext(parent)))
+			zipkinStartSpanOptions.Parent = (*model.SpanContext)(&parent)
 		}
 	}
 
 	startTime := time.Now()
 	// Time
 	if !startSpanOptions.StartTime.IsZero() {
-		zopts = append(zopts, zipkin.StartTime(startSpanOptions.StartTime))
-		startTime = startSpanOptions.StartTime
+		zipkinStartSpanOptions.StartTime = startSpanOptions.StartTime
+		zopts = append(zopts, zipkin.StartTime(zipkinStartSpanOptions.StartTime))
 	}
 
-	zopts = append(zopts, parseTagsAsZipkinOptions(startSpanOptions.Tags)...)
+	zopts = append(zopts, parseTagsAsZipkinOptions(startSpanOptions.Tags, &zipkinStartSpanOptions)...)
 
 	newSpan := t.zipkinTracer.StartSpan(operationName, zopts...)
 
@@ -87,14 +90,18 @@ func (t *tracerImpl) StartSpan(operationName string, opts ...opentracing.StartSp
 		sp.observer = observer
 	}
 
+	if t.opts.zipkinObserver != nil {
+		sp.zipkinObserver = t.opts.zipkinObserver.OnStartSpan(sp.zipkinSpan, operationName, &zipkinStartSpanOptions)
+	}
+
 	return sp
 }
 
-func parseTagsAsZipkinOptions(t map[string]interface{}) []zipkin.SpanOption {
+func parseTagsAsZipkinOptions(t map[string]interface{}, options *ZipkinStartSpanOptions) []zipkin.SpanOption {
 	zopts := make([]zipkin.SpanOption, 0)
 
-	tags := map[string]string{}
-	remoteEndpoint := &model.Endpoint{}
+	options.Tags = map[string]string{}
+	options.RemoteEndpoint = &model.Endpoint{}
 
 	var kind string
 	if val, ok := t[string(ext.SpanKind)]; ok {
@@ -112,29 +119,30 @@ func parseTagsAsZipkinOptions(t map[string]interface{}) []zipkin.SpanOption {
 			mKind == model.Producer ||
 			mKind == model.Consumer {
 			zopts = append(zopts, zipkin.Kind(mKind))
+			options.Kind = mKind
 		} else {
-			tags["span.kind"] = kind
+			options.Tags["span.kind"] = kind
 		}
 	}
 
 	if val, ok := t[string(ext.PeerService)]; ok {
 		serviceName, _ := val.(string)
-		remoteEndpoint.ServiceName = serviceName
+		options.RemoteEndpoint.ServiceName = serviceName
 	}
 
 	if val, ok := t[string(ext.PeerHostIPv4)]; ok {
 		ipv4, _ := val.(string)
-		remoteEndpoint.IPv4 = net.ParseIP(ipv4)
+		options.RemoteEndpoint.IPv4 = net.ParseIP(ipv4)
 	}
 
 	if val, ok := t[string(ext.PeerHostIPv6)]; ok {
 		ipv6, _ := val.(string)
-		remoteEndpoint.IPv6 = net.ParseIP(ipv6)
+		options.RemoteEndpoint.IPv6 = net.ParseIP(ipv6)
 	}
 
 	if val, ok := t[string(ext.PeerPort)]; ok {
 		port, _ := val.(uint16)
-		remoteEndpoint.Port = port
+		options.RemoteEndpoint.Port = port
 	}
 
 	for key, val := range t {
@@ -146,15 +154,15 @@ func parseTagsAsZipkinOptions(t map[string]interface{}) []zipkin.SpanOption {
 			continue
 		}
 
-		tags[key] = fmt.Sprint(val)
+		options.Tags[key] = fmt.Sprint(val)
 	}
 
-	if len(tags) > 0 {
-		zopts = append(zopts, zipkin.Tags(tags))
+	if len(options.Tags) > 0 {
+		zopts = append(zopts, zipkin.Tags(options.Tags))
 	}
 
-	if !remoteEndpoint.Empty() {
-		zopts = append(zopts, zipkin.RemoteEndpoint(remoteEndpoint))
+	if !options.RemoteEndpoint.Empty() {
+		zopts = append(zopts, zipkin.RemoteEndpoint(options.RemoteEndpoint))
 	}
 
 	return zopts

tracer_options.go

@@ -31,8 +31,9 @@ const (
 
 // TracerOptions allows creating a customized Tracer.
 type TracerOptions struct {
-	observer    otobserver.Observer
-	b3InjectOpt B3InjectOption
+	observer       otobserver.Observer
+	b3InjectOpt    B3InjectOption
+	zipkinObserver ZipkinObserver
 }
 
 // TracerOption allows for functional options.
@@ -46,6 +47,13 @@ func WithObserver(observer otobserver.Observer) TracerOption {
 	}
 }
 
+// WithZipkinObserver assigns an initialized zipkin observer to opts.zipkinObserver
+func WithZipkinObserver(zipkinObserver ZipkinObserver) TracerOption {
+	return func(opts *TracerOptions) {
+		opts.zipkinObserver = zipkinObserver
+	}
+}
+
 // WithB3InjectOption sets the B3 injection style if using the native OpenTracing HTTPHeadersCarrier
 func WithB3InjectOption(b3InjectOption B3InjectOption) TracerOption {
 	return func(opts *TracerOptions) {