feat: Add ability to set adapter scoped metadata

Partially addresses #40

go/adapter.go

@@ -21,6 +21,7 @@ type Adapter interface {
 type TraceEvent struct {
 	Events      []Event
 	TelemetryId TelemetryId
+	AdapterMeta interface{}
 }
 
 // Shared implementation for all Adapters

go/adapter/datadog/adapter.go

@@ -3,6 +3,7 @@ package datadog
 import (
 	"bytes"
 	"encoding/json"
+	"fmt"
 	"log"
 	"net/http"
 	"net/url"
@@ -75,9 +76,20 @@ func (d *DatadogAdapter) HandleTraceEvent(te observe.TraceEvent) {
 
 	go func() {
 		output := datadog_formatter.New()
-		// TODO: for the moment, these are hard-coded, but will transition to a programmer-
-		// controlled API to customer these values.
-		allSpans[0].Resource = "request"
+
+		if meta, ok := te.AdapterMeta.(DatadogMetadata); ok {
+			topSpan := allSpans[0]
+			if meta.ResourceName != nil {
+				topSpan.Resource = *meta.ResourceName
+			}
+			if meta.HttpUrl != nil {
+				topSpan.Meta["http.url"] = *meta.HttpUrl
+			}
+			if meta.HttpStatusCode != nil {
+				topSpan.Meta["http.status_code"] = fmt.Sprintf("%d", *meta.HttpStatusCode)
+			}
+		}
+
 		tt := d.Config.TraceType.String()
 		allSpans[0].Type = &tt
 		output.AddTrace(allSpans)
@@ -126,6 +138,13 @@ func (d *DatadogAdapter) makeCallSpans(event observe.CallEvent, parentId *uint64
 	return spans
 }
 
+type DatadogMetadata struct {
+	HttpUrl        *string
+	HttpMethod     *string
+	HttpStatusCode *int
+	ResourceName   *string
+}
+
 type DatadogSpanKind int
 
 const (

go/adapter/datadog_formatter/format.go

@@ -37,6 +37,7 @@ func NewSpan(service string, traceId uint64, parentId *uint64, name string, star
 		Duration: uint64(end.Sub(start).Nanoseconds()),
 		Service:  service,
 		Resource: name,
+		Meta:     make(map[string]string),
 	}
 	return &span
 }

go/bin/datadog/main.go

@@ -46,6 +46,20 @@ func main() {
 	}
 	defer m.Close(ctx)
 
+	// normally this metadata would be in your web-server framework
+	// or derived when you need them. we're just gonna initialize
+	// some example values here
+	resourceName := "my-resource"
+	httpUrl := "https://example.com/my-endpoint"
+	httpStatusCode := 200
+
+	meta := datadog.DatadogMetadata{
+		ResourceName:   &resourceName,
+		HttpUrl:        &httpUrl,
+		HttpStatusCode: &httpStatusCode,
+	}
+	traceCtx.Metadata(meta)
+
 	traceCtx.Finish()
 
 	time.Sleep(time.Second * 2)

go/trace_ctx.go

@@ -34,6 +34,7 @@ type TraceCtx struct {
 	Config      *Config
 	names       map[uint32]string
 	telemetryId TelemetryId
+	adapterMeta interface{}
 }
 
 // Creates a new TraceCtx. Used internally by the Adapter. The user should create the trace context from the Adapter.
@@ -59,12 +60,17 @@ func newTraceCtx(ctx context.Context, adapter *AdapterBase, r wazero.Runtime, da
 	return traceCtx, nil
 }
 
+func (t *TraceCtx) Metadata(metadata interface{}) {
+	t.adapterMeta = metadata
+}
+
 // Finish() will stop the trace and send the
 // TraceEvent payload to the adapter
 func (t *TraceCtx) Finish() {
 	traceEvent := TraceEvent{
 		Events:      t.events,
 		TelemetryId: t.telemetryId,
+		AdapterMeta: t.adapterMeta,
 	}
 	t.adapter <- traceEvent
 	// clear the trace context