Handle nil sampling config (#1292)

* Apply default sampling config when none is provided * Provide default sampling config in NewSamplingManager if non is provided * changelog entry * Update CHANGELOG.md Co-authored-by: Tyler Yahn <[email protected]> --------- Co-authored-by: Tyler Yahn <[email protected]>
open-telemetry · Nov 18, 2024 · e316695 · e316695
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -18,6 +18,7 @@ OpenTelemetry Go Automatic Instrumentation adheres to [Semantic Versioning](http
 ### Fixed
 
 - Don't include `db.query.text` attribute in `database/sql` if the query string is empty or not collected. ([#1246](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1246))
+- Handle a `ConfigProvider` which doesn't provide a sampling config in the initial configuration by applying the default sampler. ([#1292](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1292))
 
 ### Removed
 

diff --git a/internal/pkg/instrumentation/probe/sampling/sampling.go b/internal/pkg/instrumentation/probe/sampling/sampling.go
@@ -206,6 +206,10 @@ func NewSamplingManager(c *ebpf.Collection, conf *Config) (*Manager, error) {
 		ActiveSamplerMap:  probeActiveSampler,
 	}
 
+	if conf == nil {
+		conf = DefaultConfig()
+	}
+
 	err := m.applyConfig(conf)
 	if err != nil {
 		return nil, err
@@ -215,6 +219,10 @@ func NewSamplingManager(c *ebpf.Collection, conf *Config) (*Manager, error) {
 }
 
 func (m *Manager) applyConfig(conf *Config) error {
+	if conf == nil {
+		return fmt.Errorf("cannot apply nil config")
+	}
+
 	samplerIDs := make([]SamplerID, 0, len(conf.Samplers))
 	configs := make([]SamplerConfig, 0, len(conf.Samplers))
 	for id, samplerConfig := range conf.Samplers {

diff --git a/internal/pkg/instrumentation/probe/sampling/sampling_linux_test.go b/internal/pkg/instrumentation/probe/sampling/sampling_linux_test.go
@@ -127,4 +127,28 @@ func TestEBPFNewSamplingConfigDefault(t *testing.T) {
 		assert.Equal(t, SamplerTraceIDRatio, samplersConfigInMap.SamplerType)
 		assert.Equal(t, TraceIDRatioConfig{42}, samplersConfigInMap.Config)
 	})
+
+	t.Run("nil config", func(t *testing.T) {
+		m, err := NewSamplingManager(c, nil)
+		if !assert.NoError(t, err) {
+			return
+		}
+
+		assert.Equal(t, m.currentSamplerID, ParentBasedID)
+
+		var activeSamplerIDInMap SamplerID
+		err = m.ActiveSamplerMap.Lookup(uint32(0), &activeSamplerIDInMap)
+		if !assert.NoError(t, err) {
+			return
+		}
+		assert.Equal(t, activeSamplerIDInMap, ParentBasedID)
+
+		var samplersConfigInMap SamplerConfig
+		err = m.samplersConfigMap.Lookup(uint32(ParentBasedID), &samplersConfigInMap)
+		if !assert.NoError(t, err) {
+			return
+		}
+		assert.Equal(t, samplersConfigInMap.SamplerType, SamplerParentBased)
+		assert.Equal(t, samplersConfigInMap.Config, DefaultParentBasedSampler())
+	})
 }