ddtrace/tracer: remove agent_psr when rule_psr is set

ddtrace/tracer/rules_sampler.go

@@ -518,7 +518,8 @@ func (rs *traceRulesSampler) sampleRules(span *span) bool {
 }
 
 func (rs *traceRulesSampler) applyRate(span *span, rate float64, now time.Time, sampler samplernames.SamplerName) {
-	span.SetTag(keyRulesSamplerAppliedRate, rate)
+	span.setMetric(keyRulesSamplerAppliedRate, rate)
+	delete(span.Metrics, keySamplingPriorityRate)
 	if !sampledByRate(span.TraceID, rate) {
 		span.setSamplingPriority(ext.PriorityUserReject, sampler)
 		return
@@ -614,6 +615,7 @@ func (rs *singleSpanRulesSampler) apply(span *span) bool {
 					return false
 				}
 			}
+			delete(span.Metrics, keySamplingPriorityRate)
 			span.setMetric(keySpanSamplingMechanism, float64(samplernames.SingleSpan))
 			span.setMetric(keySingleSpanSamplingRuleRate, rate)
 			if rule.MaxPerSecond != 0 {

ddtrace/tracer/sampler_test.go

@@ -1065,6 +1065,19 @@ func TestRulesSampler(t *testing.T) {
 		s.Finish()
 		assert.EqualValues(t, s.(*span).Metrics[keySamplingPriority], 2)
 	})
+
+	t.Run("no-agent_psr-with-rules-sampling", func(t *testing.T) {
+		t.Setenv("DD_TRACE_SAMPLING_RULES", `[{"resource": "keep_me", "sample_rate": 0}]`)
+		_, _, _, stop := startTestTracer(t)
+		defer stop()
+
+		s, _ := StartSpanFromContext(context.Background(), "whatever")
+		s.SetTag(ext.ResourceName, "keep_me")
+		s.Finish()
+		span := s.(*span)
+		assert.NotContains(t, span.Metrics, keySamplingPriorityRate)
+		assert.Contains(t, span.Metrics, keyRulesSamplerAppliedRate)
+	})
 }
 
 func TestSamplingRuleUnmarshal(t *testing.T) {