[processor/tailsampling] Fix composite policy with inverse matching (o…

…pen-telemetry#9793)

Co-authored-by: Alex Boten <[email protected]>

CHANGELOG.md

@@ -31,6 +31,7 @@
 - `dynatraceexporter`: Ensure min is always less than or equal to mean and max is always greater or equal to mean for histogram estimation. (#10257)
 - `resourcedetectionprocessor`: GCP resource detector now properly detects zone/region on GKE (#10347)
 - `resourcedetectionprocessor`: GCP resource detector no longer fails to detect resource when using workload identity (#10486)
+- `tailsamplingprocessor`: Fix composite sampler with inverse policy
 
 ## v0.52.0
 

processor/tailsamplingprocessor/internal/sampling/composite.go

@@ -109,7 +109,7 @@ func (c *Composite) Evaluate(traceID pcommon.TraceID, trace *TraceData) (Decisio
  return Unspecified, err
  }
 
- if decision == Sampled {
+ if decision == Sampled || decision == InvertSampled {
  // The subpolicy made a decision to Sample. Now we need to make our decision.
 
  // Calculate resulting SPS counter if we decide to sample this trace

processor/tailsamplingprocessor/internal/sampling/composite_test.go

@@ -161,6 +161,25 @@ func TestCompositeEvaluatorSampled_AlwaysSampled(t *testing.T) {
  }
 }
 
+func TestCompositeEvaluatorInverseSampled_AlwaysSampled(t *testing.T) {
+
+ // The first policy does not match, the second matches through invert
+ n1 := NewStringAttributeFilter(zap.NewNop(), "tag", []string{"foo"}, false, 0, false)
+ n2 := NewStringAttributeFilter(zap.NewNop(), "tag", []string{"foo"}, false, 0, true)
+ c := NewComposite(zap.NewNop(), 10, []SubPolicyEvalParams{{n1, 20}, {n2, 20}}, FakeTimeProvider{})
+
+ for i := 1; i <= 10; i++ {
+ trace := createTrace()
+
+ decision, err := c.Evaluate(traceID, trace)
+ require.NoError(t, err, "Failed to evaluate composite policy: %v", err)
+
+ // The second policy is AlwaysSample, so the decision should be Sampled.
+ expected := Sampled
+ assert.Equal(t, decision, expected)
+ }
+}
+
 func TestCompositeEvaluatorThrottling(t *testing.T) {
 
  // Create only one subpolicy, with 100% Sampled policy.