Pass policy name to NewEvaluator

It can be useful for an instance of an evaluator to know the name of the
policy for debugging or reporting purposes. Since a single type can be
used multiple times with different configuration.

Author: csmarchbanks

processor/tailsamplingprocessor/pkg/samplingpolicy/samplingpolicy.go

@@ -63,5 +63,5 @@ type Evaluator interface {
 }
 
 type Extension interface {
-	NewEvaluator(cfg map[string]any) (Evaluator, error)
+	NewEvaluator(policyName string, cfg map[string]any) (Evaluator, error)
 }

processor/tailsamplingprocessor/processor.go

@@ -276,7 +276,7 @@ func getSharedPolicyEvaluator(settings component.TelemetrySettings, cfg *sharedP
 		t := string(cfg.Type)
 		extension, ok := policyExtensions[t]
 		if ok {
-			evaluator, err := extension.NewEvaluator(cfg.ExtensionCfg[t])
+			evaluator, err := extension.NewEvaluator(cfg.Name, cfg.ExtensionCfg[t])
 			if err != nil {
 				return nil, fmt.Errorf("unable to load extension %s: %w", t, err)
 			}

processor/tailsamplingprocessor/processor_test.go

@@ -1068,6 +1068,7 @@ func TestExtension(t *testing.T) {
 
 	tsp := p.(*tailSamplingSpanProcessor)
 	assert.Len(t, tsp.policies, 1)
+	assert.Equal(t, "extension", host.extension.policyName)
 	assert.Equal(t, map[string]any{"foo": "bar"}, host.extension.cfg)
 }
 
@@ -1085,13 +1086,15 @@ func (h *extensionHost) GetExtensions() map[component.ID]component.Component {
 }
 
 type extension struct {
-	cfg map[string]any
+	policyName string
+	cfg        map[string]any
 }
 
 var _ samplingpolicy.Extension = &extension{}
 
 // NewEvaluator implements samplingpolicy.Extension.
-func (e *extension) NewEvaluator(cfg map[string]any) (samplingpolicy.Evaluator, error) {
+func (e *extension) NewEvaluator(policyName string, cfg map[string]any) (samplingpolicy.Evaluator, error) {
+	e.policyName = policyName
 	e.cfg = cfg
 	return nil, nil
 }