Add integration test for ErrTraceNotFound

plugin/storage/badger/spanstore/read_write_test.go

@@ -306,7 +306,7 @@ func TestFindNothing(t *testing.T) {
 		assert.Equal(t, 0, len(trs))
 
 		tr, err := sr.GetTrace(context.Background(), model.TraceID{High: 0, Low: 0})
-		assert.NoError(t, err)
+		assert.Equal(t, spanstore.ErrTraceNotFound, err)
 		assert.Nil(t, tr)
 	})
 }

plugin/storage/badger/spanstore/reader.go

@@ -164,7 +164,7 @@ func (r *TraceReader) GetTrace(ctx context.Context, traceID model.TraceID) (*mod
 		return traces[0], nil
 	}
 
-	return nil, nil
+	return nil, spanstore.ErrTraceNotFound
 }
 
 // scanTimeRange returns all the Traces found between startTs and endTs

plugin/storage/integration/integration.go

@@ -188,6 +188,13 @@ func (s *StorageIntegration) testGetTrace(t *testing.T) {
 	if !assert.True(t, found) {
 		CompareTraces(t, expected, actual)
 	}
+
+	t.Run("NotFound error", func(t *testing.T) {
+		fakeTraceID := model.TraceID{High: 0, Low: 0}
+		trace, err := s.SpanReader.GetTrace(context.Background(), fakeTraceID)
+		assert.Equal(t, spanstore.ErrTraceNotFound, err)
+		assert.Nil(t, trace)
+	})
 }
 
 func (s *StorageIntegration) testFindTraces(t *testing.T) {

storage/spanstore/interface.go

@@ -35,10 +35,31 @@ type Writer interface {
 
 // Reader finds and loads traces and other data from storage.
 type Reader interface {
+	// GetTrace retrieves the trace with a given id.
+	//
+	// If no spans are stored for this trace, it returns ErrTraceNotFound.
 	GetTrace(ctx context.Context, traceID model.TraceID) (*model.Trace, error)
+
+	// GetServices returns all service names known to the backend from spans
+	// within its retention period.
 	GetServices(ctx context.Context) ([]string, error)
+
+	// GetOperations returns all operation names for a given service
+	// known to the backend from spans within its retention period.
 	GetOperations(ctx context.Context, query OperationQueryParameters) ([]Operation, error)
+
+	// FindTraces returns all traces matching query parameters. There's currently
+	// an implementation-dependent abiguity whether all query filters (such as
+	// multiple tags) must apply to the same span within a trace, or can be satisfied
+	// by different spans.
+	//
+	// If no matching traces are found, the function returns (nil, nil).
 	FindTraces(ctx context.Context, query *TraceQueryParameters) ([]*model.Trace, error)
+
+	// FindTraceIDs does the same search as FindTraces, but returns only the list
+	// of matching trace IDs.
+	//
+	// If no matching traces are found, the function returns (nil, nil).
 	FindTraceIDs(ctx context.Context, query *TraceQueryParameters) ([]model.TraceID, error)
 }