event: Ensure event priorities are propagated to Datadog backend.

event/processor.go

@@ -83,6 +83,10 @@ func (p *Processor) Process(t model.ProcessedTrace) (events []*model.Event, numE
 		// As well as the rates of sampling done during this processing
 		event.SetExtractionSampleRate(extractionRate)
 		event.SetMaxEPSSampleRate(epsRate)
+		if hasPriority {
+			// Make sure to set the sampling priority on the event span so that this gets propagated to the backend.
+			event.Span.SetSamplingPriority(priority)
+		}
 	}
 
 	return

event/processor_test.go

@@ -89,6 +89,12 @@ func TestProcessor(t *testing.T) {
 				assert.EqualValues(test.expectedSampledPct, event.GetMaxEPSSampleRate())
 				assert.EqualValues(testClientSampleRate, event.GetClientTraceSampleRate())
 				assert.EqualValues(testPreSampleRate, event.GetPreSampleRate())
+
+				eventSpanPriority, ok := event.Span.GetSamplingPriority()
+				if !ok {
+					eventSpanPriority = model.PriorityNone
+				}
+				assert.EqualValues(test.priority, eventSpanPriority)
 			}
 		})
 	}