From d0985c49d493ce7790ea92fbeb0ec3adeae6ebc1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dario=20Casta=C3=B1=C3=A9?= <dario.castane@datadoghq.com>
Date: Tue, 28 Jan 2025 12:19:32 +0100
Subject: [PATCH] feat(ddtrace/tracer): add `Datadog-External-Env` default HTTP
 header

---
 ddtrace/tracer/transport.go | 3 +++
 internal/env.go             | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/ddtrace/tracer/transport.go b/ddtrace/tracer/transport.go
index 222f6c8b70..1cf84254ad 100644
--- a/ddtrace/tracer/transport.go
+++ b/ddtrace/tracer/transport.go
@@ -104,6 +104,9 @@ func newHTTPTransport(url string, client *http.Client) *httpTransport {
 	if eid := internal.EntityID(); eid != "" {
 		defaultHeaders["Datadog-Entity-ID"] = eid
 	}
+	if extEnv := internal.ExternalEnvironment(); extEnv != "" {
+		defaultHeaders["Datadog-External-Env"] = extEnv
+	}
 	return &httpTransport{
 		traceURL: fmt.Sprintf("%s/v0.4/traces", url),
 		statsURL: fmt.Sprintf("%s/v0.6/stats", url),
diff --git a/internal/env.go b/internal/env.go
index 2e760526ac..97951e0a66 100644
--- a/internal/env.go
+++ b/internal/env.go
@@ -133,3 +133,7 @@ func BoolVal(val string, def bool) bool {
 	}
 	return v
 }
+
+func ExternalEnvironment() string {
+	return os.Getenv("DD_EXTERNAL_ENV")
+}