feat: Add support for Dynamic Sampling

client.go

@@ -624,12 +624,12 @@ func (client *Client) prepareEvent(event *Event, hint *EventHint, scope EventMod
 
 	event.Platform = "go"
 	event.Sdk = SdkInfo{
-		Name:         "sentry.go",
-		Version:      Version,
+		Name:         SDKIdentifier,
+		Version:      SDKVersion,
 		Integrations: client.listIntegrations(),
 		Packages: []SdkPackage{{
 			Name:    "sentry-go",
-			Version: Version,
+			Version: SDKVersion,
 		}},
 	}
 

client_test.go

@@ -266,14 +266,14 @@ func TestCaptureEvent(t *testing.T) {
 		Platform:   "go",
 		Sdk: SdkInfo{
 			Name:         "sentry.go",
-			Version:      Version,
+			Version:      SDKVersion,
 			Integrations: []string{},
 			Packages: []SdkPackage{
 				{
 					// FIXME: name format doesn't follow spec in
 					// https://docs.sentry.io/development/sdk-dev/event-payloads/sdk/
 					Name:    "sentry-go",
-					Version: Version,
+					Version: SDKVersion,
 				},
 				// TODO: perhaps the list of packages is incomplete or there
 				// should not be any package at all. We may include references

dynamic_sampling_context.go

@@ -0,0 +1,45 @@
+package sentry
+
+import (
+	"strings"
+
+	"github.com/getsentry/sentry-go/internal/otel/baggage"
+)
+
+const (
+	sentryPrefix = "sentry-"
+)
+
+// DynamicSamplingContext holds information about the current event that can be used to make dynamic sampling decisions.
+type DynamicSamplingContext struct {
+	Entries map[string]string
+	Frozen  bool
+}
+
+func NewDynamicSamplingContext(header []byte) (DynamicSamplingContext, error) {
+	bag, err := baggage.Parse(string(header))
+	if err != nil {
+		return DynamicSamplingContext{}, err
+	}
+
+	entries := map[string]string{}
+	for _, member := range bag.Members() {
+		// We only store baggage members if their key starts with "sentry-".
+		if k, v := member.Key(), member.Value(); strings.HasPrefix(k, sentryPrefix) {
+			entries[strings.TrimPrefix(k, sentryPrefix)] = v
+		}
+	}
+
+	return DynamicSamplingContext{
+		Entries: entries,
+		Frozen:  true,
+	}, nil
+}
+
+func (d DynamicSamplingContext) HasEntries() bool {
+	return len(d.Entries) > 0
+}
+
+func (d DynamicSamplingContext) String() string {
+	return ""
+}

dynamic_sampling_context_test.go

@@ -0,0 +1,50 @@
+package sentry
+
+import (
+	"testing"
+)
+
+func TestNewDynamicSamplingContext(t *testing.T) {
+	tests := []struct {
+		input []byte
+		want  DynamicSamplingContext
+	}{
+		{
+			input: []byte(""),
+			want: DynamicSamplingContext{
+				Frozen:  true,
+				Entries: map[string]string{},
+			},
+		},
+		{
+			input: []byte("sentry-trace_id=d49d9bf66f13450b81f65bc51cf49c03,sentry-public_key=public,sentry-sample_rate=1"),
+			want: DynamicSamplingContext{
+				Frozen: true,
+				Entries: map[string]string{
+					"trace_id":    "d49d9bf66f13450b81f65bc51cf49c03",
+					"public_key":  "public",
+					"sample_rate": "1",
+				},
+			},
+		},
+		{
+			input: []byte("sentry-trace_id=d49d9bf66f13450b81f65bc51cf49c03,sentry-public_key=public,sentry-sample_rate=1,foo=bar;foo;bar;bar=baz"),
+			want: DynamicSamplingContext{
+				Frozen: true,
+				Entries: map[string]string{
+					"trace_id":    "d49d9bf66f13450b81f65bc51cf49c03",
+					"public_key":  "public",
+					"sample_rate": "1",
+				},
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		got, err := NewDynamicSamplingContext(tc.input)
+		if err != nil {
+			t.Fatal(err)
+		}
+		assertEqual(t, got, tc.want)
+	}
+}

interfaces.go

@@ -215,6 +215,18 @@ type Exception struct {
 	Stacktrace *Stacktrace `json:"stacktrace,omitempty"`
 }
 
+type SDKMetaDataKey = string
+
+const (
+	DynamicSamplingContextKey SDKMetaDataKey = "DynamicSamplingContext"
+)
+
+// SDKMetaData is a struct to stash data which is needed at some point in the SDK's event processing pipeline
+// but which shouldn't get send to Sentry.
+type SDKMetaData = struct {
+	DynamicSamplingContextKey DynamicSamplingContext
+}
+
 // EventID is a hexadecimal string representing a unique uuid4 for an Event.
 // An EventID must be 32 characters long, lowercase and not have any dashes.
 type EventID string
@@ -251,6 +263,10 @@ type Event struct {
 	Type      string    `json:"type,omitempty"`
 	StartTime time.Time `json:"start_timestamp"`
 	Spans     []*Span   `json:"spans,omitempty"`
+
+	// The fields below are not part of the final JSON payload.
+
+	SDKMetaData SDKMetaData `json:"-"`
 }
 
 // TODO: Event.Contexts map[string]interface{} => map[string]EventContext,