Adding locks where context is accessed

This commit addresses data race issues where span.context is accessed without locks in methods which can be called concurrently with method setBaggageItem which modifies context

Per issue jaegertracing#526

Signed-off-by: Keerthana Selvakumar <keerukeerthana8@gmail.com>

span.go

@@ -99,6 +99,9 @@ func (s *Span) SetTag(key string, value interface{}) opentracing.Span {
 	return s.setTagInternal(key, value, true)
 }
 
+// setTagInternal sets tags in a thread-safe manner if lock param is set to true.
+// lock param can be set to false if concurrent access in not expected like when span is created.
+// The caller shouldn't obtain any lock on the span while calling this as it will lead to a deadlock.
 func (s *Span) setTagInternal(key string, value interface{}, lock bool) opentracing.Span {
 	s.observer.OnSetTag(key, value)
 	if key == string(ext.SamplingPriority) && !setSamplingPriority(s, value) {
@@ -120,8 +123,8 @@ func (s *Span) setTagInternal(key string, value interface{}, lock bool) opentrac
 
 // SpanContext returns span context
 func (s *Span) SpanContext() SpanContext {
-	s.Lock()
-	defer s.Unlock()
+	s.RLock()
+	defer s.RUnlock()
 	return s.context
 }
 
@@ -345,7 +348,7 @@ func (s *Span) FinishWithOptions(options opentracing.FinishOptions) {
 		decision := s.tracer.sampler.OnFinishSpan(s)
 		s.applySamplingDecision(decision, true)
 	}
-	if s.context.IsSampled() {
+	if s.SpanContext().IsSampled() {
 		s.Lock()
 		s.fixLogsIfDropped()
 		if len(options.LogRecords) > 0 || len(options.BulkLogData) > 0 {
@@ -366,8 +369,8 @@ func (s *Span) FinishWithOptions(options opentracing.FinishOptions) {
 
 // Context implements opentracing.Span API
 func (s *Span) Context() opentracing.SpanContext {
-	s.Lock()
-	defer s.Unlock()
+	s.RLock()
+	defer s.RUnlock()
 	return s.context
 }
 
@@ -427,10 +430,10 @@ func (s *Span) serviceName() string {
 
 func (s *Span) applySamplingDecision(decision SamplingDecision, lock bool) {
 	if !decision.Retryable {
-		s.context.samplingState.setFinal()
+		s.SpanContext().samplingState.setFinal()
 	}
 	if decision.Sample {
-		s.context.samplingState.setSampled()
+		s.SpanContext().samplingState.setSampled()
 		if len(decision.Tags) > 0 {
 			if lock {
 				s.Lock()
@@ -445,12 +448,12 @@ func (s *Span) applySamplingDecision(decision SamplingDecision, lock bool) {
 
 // Span can be written to if it is sampled or the sampling decision has not been finalized.
 func (s *Span) isWriteable() bool {
-	state := s.context.samplingState
+	state := s.SpanContext().samplingState
 	return !state.isFinal() || state.isSampled()
 }
 
 func (s *Span) isSamplingFinalized() bool {
-	return s.context.samplingState.isFinal()
+	return s.SpanContext().samplingState.isFinal()
 }
 
 // setSamplingPriority returns true if the flag was updated successfully, false otherwise.
@@ -469,26 +472,25 @@ func setSamplingPriority(s *Span, value interface{}) bool {
 	if !ok {
 		return false
 	}
+	ctx := s.SpanContext()
 	if val == 0 {
-		s.context.samplingState.unsetSampled()
-		s.context.samplingState.setFinal()
+		ctx.samplingState.unsetSampled()
+		ctx.samplingState.setFinal()
 		return true
 	}
 	if s.tracer.options.noDebugFlagOnForcedSampling {
-		s.context.samplingState.setSampled()
-		s.context.samplingState.setFinal()
+		ctx.samplingState.setSampled()
+		ctx.samplingState.setFinal()
 		return true
 	} else if s.tracer.isDebugAllowed(s.operationName) {
-		s.context.samplingState.setDebugAndSampled()
-		s.context.samplingState.setFinal()
+		ctx.samplingState.setDebugAndSampled()
+		ctx.samplingState.setFinal()
 		return true
 	}
 	return false
 }
 
 // EnableFirehose enables firehose flag on the span context
 func EnableFirehose(s *Span) {
-	s.Lock()
-	defer s.Unlock()
-	s.context.samplingState.setFirehose()
+	s.SpanContext().samplingState.setFirehose()
 }

span_test.go

@@ -363,7 +363,6 @@ func TestSpan_References(t *testing.T) {
 }
 
 func TestSpanContextRaces(t *testing.T) {
-	t.Skip("Skipped: test will panic with -race, see https://github.com/jaegertracing/jaeger-client-go/issues/526")
 	tracer, closer := NewTracer("test", NewConstSampler(true), NewNullReporter())
 	defer closer.Close()
 
@@ -395,6 +394,16 @@ func TestSpanContextRaces(t *testing.T) {
 	go accessor(func() {
 		span.BaggageItem("k")
 	})
+	go accessor(func() {
+		ext.SamplingPriority.Set(span, 0)
+	})
+	go accessor(func() {
+		EnableFirehose(span)
+	})
+	go accessor(func() {
+		span.SpanContext().samplingState.setFlag(flagDebug)
+	})
 	time.Sleep(100 * time.Millisecond)
+	span.Finish()
 	close(end)
 }

tracer.go

@@ -439,7 +439,7 @@ func (t *Tracer) emitNewSpanMetrics(sp *Span, newTrace bool) {
 func (t *Tracer) reportSpan(sp *Span) {
 	if !sp.isSamplingFinalized() {
 		t.metrics.SpansFinishedDelayedSampling.Inc(1)
-	} else if sp.context.IsSampled() {
+	} else if sp.SpanContext().IsSampled() {
 		t.metrics.SpansFinishedSampled.Inc(1)
 	} else {
 		t.metrics.SpansFinishedNotSampled.Inc(1)
@@ -448,7 +448,7 @@ func (t *Tracer) reportSpan(sp *Span) {
 	// Note: if the reporter is processing Span asynchronously then it needs to Retain() the span,
 	// and then Release() it when no longer needed.
 	// Otherwise, the span may be reused for another trace and its data may be overwritten.
-	if sp.context.IsSampled() {
+	if sp.SpanContext().IsSampled() {
 		t.reporter.Report(sp)
 	}