Support "Self" Span Reference (#411)

* POC: Self Referenced Span refs #397 Signed-off-by: Daniel Mican <[email protected]> * Self Ref Span: Moves SelfRef -> constants Signed-off-by: Daniel Mican <[email protected]> * SelfRef: removes extra pointer Signed-off-by: Daniel Mican <[email protected]> * SelfRef: README Signed-off-by: Daniel Mican <[email protected]> * SelfRef: README Signed-off-by: Daniel Mican <[email protected]> * SelfRef: startSpan unit test Signed-off-by: Daniel Mican <[email protected]> * SelfRef: startSpanWithOptions check for selRef before tracking references. Provides a selfRef factory method hidningn constant/implementation details Signed-off-by: Daniel Mican <[email protected]> * SelfRef: Lint Signed-off-by: Daniel Mican <[email protected]> * SelfRef: README update Signed-off-by: Daniel Mican <[email protected]> * SelfRef: Rebuild, github timeout Signed-off-by: Daniel Mican <[email protected]> * SelfRef: Rebuild Signed-off-by: Daniel Mican <[email protected]>
jaegertracing · Aug 7, 2019 · 201832f · 201832f
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diff --git a/README.md b/README.md
@@ -253,6 +253,24 @@ by a lot of Zipkin tracers. This means that you can use Jaeger in conjunction wi
 
 However it is not the default propagation format, see [here](zipkin/README.md#NewZipkinB3HTTPHeaderPropagator) how to set it up.
 
+## SelfRef
+
+Jaeger Tracer supports an additional [reference](https://github.com/opentracing/specification/blob/1.1/specification.md#references-between-spans)
+type call `Self`. This allows a caller to provide an already established `SpanContext`.
+This allows loading and continuing spans/traces from offline (ie log-based) storage. The `Self` reference
+bypasses trace and span id generation.
+
+
+Usage requires passing in a `SpanContext` and the jaeger `Self` reference type:
+```
+span := tracer.StartSpan(
+    "continued_span",
+    SelfRef(yourSpanContext),
+)
+...
+defer span.finish()
+```
+
 ## License
 
 [Apache 2.0 License](LICENSE).

diff --git a/constants.go b/constants.go
@@ -14,6 +14,8 @@
 
 package jaeger
 
+import "github.com/opentracing/opentracing-go"
+
 const (
 	// JaegerClientVersion is the version of the client library reported as Span tag.
 	JaegerClientVersion = "Go-2.16.1dev"
@@ -85,4 +87,8 @@ const (
 
 	// DefaultMaxTagValueLength is the default max length of byte array or string allowed in the tag value.
 	DefaultMaxTagValueLength = 256
+
+	// SelfRefType is a jaeger specific reference type that supports creating a span
+	// with an already defined context.
+	selfRefType opentracing.SpanReferenceType = 99
 )
diff --git a/tracer.go b/tracer.go
@@ -222,20 +222,30 @@ func (t *Tracer) startSpanWithOptions(
 	var references []Reference
 	var parent SpanContext
 	var hasParent bool // need this because `parent` is a value, not reference
+	var ctx SpanContext
+	var isSelfRef bool
 	for _, ref := range options.References {
-		ctx, ok := ref.ReferencedContext.(SpanContext)
+		ctxRef, ok := ref.ReferencedContext.(SpanContext)
 		if !ok {
 			t.logger.Error(fmt.Sprintf(
 				"Reference contains invalid type of SpanReference: %s",
 				reflect.ValueOf(ref.ReferencedContext)))
 			continue
 		}
-		if !isValidReference(ctx) {
+		if !isValidReference(ctxRef) {
+			continue
+		}
+
+		if ref.Type == selfRefType {
+			isSelfRef = true
+			ctx = ctxRef
 			continue
 		}
-		references = append(references, Reference{Type: ref.Type, Context: ctx})
+
+		references = append(references, Reference{Type: ref.Type, Context: ctxRef})
+
 		if !hasParent {
-			parent = ctx
+			parent = ctxRef
 			hasParent = ref.Type == opentracing.ChildOfRef
 		}
 	}
@@ -251,42 +261,43 @@ func (t *Tracer) startSpanWithOptions(
 	}
 
 	var samplerTags []Tag
-	var ctx SpanContext
 	newTrace := false
-	if !hasParent || !parent.IsValid() {
-		newTrace = true
-		ctx.traceID.Low = t.randomID()
-		if t.options.gen128Bit {
-			ctx.traceID.High = t.options.highTraceIDGenerator()
-		}
-		ctx.spanID = SpanID(ctx.traceID.Low)
-		ctx.parentID = 0
-		ctx.flags = byte(0)
-		if hasParent && parent.isDebugIDContainerOnly() && t.isDebugAllowed(operationName) {
-			ctx.flags |= (flagSampled | flagDebug)
-			samplerTags = []Tag{{key: JaegerDebugHeader, value: parent.debugID}}
-		} else if sampled, tags := t.sampler.IsSampled(ctx.traceID, operationName); sampled {
-			ctx.flags |= flagSampled
-			samplerTags = tags
-		}
-	} else {
-		ctx.traceID = parent.traceID
-		if rpcServer && t.options.zipkinSharedRPCSpan {
-			// Support Zipkin's one-span-per-RPC model
-			ctx.spanID = parent.spanID
-			ctx.parentID = parent.parentID
+	if !isSelfRef {
+		if !hasParent || !parent.IsValid() {
+			newTrace = true
+			ctx.traceID.Low = t.randomID()
+			if t.options.gen128Bit {
+				ctx.traceID.High = t.options.highTraceIDGenerator()
+			}
+			ctx.spanID = SpanID(ctx.traceID.Low)
+			ctx.parentID = 0
+			ctx.flags = byte(0)
+			if hasParent && parent.isDebugIDContainerOnly() && t.isDebugAllowed(operationName) {
+				ctx.flags |= (flagSampled | flagDebug)
+				samplerTags = []Tag{{key: JaegerDebugHeader, value: parent.debugID}}
+			} else if sampled, tags := t.sampler.IsSampled(ctx.traceID, operationName); sampled {
+				ctx.flags |= flagSampled
+				samplerTags = tags
+			}
 		} else {
-			ctx.spanID = SpanID(t.randomID())
-			ctx.parentID = parent.spanID
+			ctx.traceID = parent.traceID
+			if rpcServer && t.options.zipkinSharedRPCSpan {
+				// Support Zipkin's one-span-per-RPC model
+				ctx.spanID = parent.spanID
+				ctx.parentID = parent.parentID
+			} else {
+				ctx.spanID = SpanID(t.randomID())
+				ctx.parentID = parent.spanID
+			}
+			ctx.flags = parent.flags
 		}
-		ctx.flags = parent.flags
-	}
-	if hasParent {
-		// copy baggage items
-		if l := len(parent.baggage); l > 0 {
-			ctx.baggage = make(map[string]string, len(parent.baggage))
-			for k, v := range parent.baggage {
-				ctx.baggage[k] = v
+		if hasParent {
+			// copy baggage items
+			if l := len(parent.baggage); l > 0 {
+				ctx.baggage = make(map[string]string, len(parent.baggage))
+				for k, v := range parent.baggage {
+					ctx.baggage[k] = v
+				}
 			}
 		}
 	}
@@ -453,3 +464,13 @@ func (t *Tracer) setBaggage(sp *Span, key, value string) {
 func (t *Tracer) isDebugAllowed(operation string) bool {
 	return t.debugThrottler.IsAllowed(operation)
 }
+
+// SelfRef creates an opentracing compliant SpanReference from a jaeger
+// SpanContext. This is a factory function in order to encapsulate jaeger specific
+// types.
+func SelfRef(ctx SpanContext) opentracing.SpanReference {
+	return opentracing.SpanReference{
+		Type:              selfRefType,
+		ReferencedContext: ctx,
+	}
+}
diff --git a/tracer_test.go b/tracer_test.go
@@ -237,6 +237,24 @@ func (s *tracerSuite) TestRandomIDNotZero() {
 	rng.Seed(1) // for test coverage
 }
 
+func (s *tracerSuite) TestReferenceSelfUsesProvidedContext() {
+	ctx := NewSpanContext(
+		TraceID{
+			High: 1,
+			Low:  2,
+		},
+		SpanID(2),
+		SpanID(1),
+		false,
+		nil,
+	)
+	sp1 := s.tracer.StartSpan(
+		"continued_span",
+		SelfRef(ctx),
+	)
+	s.Equal(ctx, sp1.(*Span).context)
+}
+
 func TestTracerOptions(t *testing.T) {
 	t1, e := time.Parse(time.RFC3339, "2012-11-01T22:08:41+00:00")
 	assert.NoError(t, e)