feat: add extra_attrs to tesla middleware

instrumentation/opentelemetry_tesla/lib/middleware/opentelemetry_tesla_middleware.ex

@@ -17,6 +17,7 @@ defmodule Tesla.Middleware.OpenTelemetry do
     Defaults to calling `:otel_propagator_text_map.get_text_map_injector/0`
     - `:mark_status_ok` - configures spans with a list of expected HTTP error codes to be marked as `ok`,
     not as an error-containing spans
+    - `:trace_attrs` - trace attributes to be added to the span.
   """
 
   alias OpenTelemetry.SemanticConventions.Trace
@@ -28,13 +29,14 @@ defmodule Tesla.Middleware.OpenTelemetry do
 
   def call(env, next, opts) do
     span_name = get_span_name(env, Keyword.get(opts, :span_name))
+    trace_attrs = Keyword.get(opts, :trace_attrs, %{})
 
     OpenTelemetry.Tracer.with_span span_name, %{kind: :client} do
       env
       |> maybe_put_additional_ok_statuses(opts[:mark_status_ok])
       |> maybe_propagate(Keyword.get(opts, :propagator, :opentelemetry.get_text_map_injector()))
       |> Tesla.run(next)
-      |> set_span_attributes()
+      |> set_span_attributes(trace_attrs)
       |> handle_result()
     end
   end
@@ -73,13 +75,15 @@ defmodule Tesla.Middleware.OpenTelemetry do
 
   defp maybe_put_additional_ok_statuses(env, _additional_ok_statuses), do: env
 
-  defp set_span_attributes({_, %Tesla.Env{} = env} = result) do
-    OpenTelemetry.Tracer.set_attributes(build_attrs(env))
+  defp set_span_attributes({_, %Tesla.Env{} = env} = result, trace_attrs) do
+    trace_attrs
+    |> Map.merge(build_attrs(env))
+    |> OpenTelemetry.Tracer.set_attributes()
 
     result
   end
 
-  defp set_span_attributes(result) do
+  defp set_span_attributes(result, _trace_attrs) do
     result
   end
 

instrumentation/opentelemetry_tesla/test/middleware/opentelemetry_tesla_middleware_test.exs

@@ -163,6 +163,35 @@ defmodule Tesla.Middleware.OpenTelemetryTest do
     end
   end
 
+  test "span with trace attrs", %{bypass: bypass} do
+    defmodule TestClient do
+      def get(client) do
+        Tesla.get(client, "/users/")
+      end
+
+      def client(url) do
+        middleware = [
+          {Tesla.Middleware.BaseUrl, url},
+          {Tesla.Middleware.OpenTelemetry, trace_attrs: %{"peer.service" => "myservicename"}}
+        ]
+
+        Tesla.client(middleware)
+      end
+    end
+
+    Bypass.expect_once(bypass, "GET", "/users", fn conn ->
+      Plug.Conn.resp(conn, 204, "")
+    end)
+
+    bypass.port
+    |> endpoint_url()
+    |> TestClient.client()
+    |> TestClient.get()
+
+    assert_receive {:span, span(name: "HTTP GET", attributes: attributes)}
+    assert %{"peer.service" => "myservicename"} = :otel_attributes.map(attributes)
+  end
+
   test "Records spans for Tesla HTTP client", %{bypass: bypass} do
     defmodule TestClient do
       def get(client) do