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
+    - `:extra_attrs` - extra span attributes
   """
 
   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))
+    extra_attrs = Keyword.get(opts, :extra_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(extra_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, extra_attrs) do
+    extra_attrs
+    |> Map.merge(build_attrs(env))
+    |> OpenTelemetry.Tracer.set_attributes()
 
     result
   end
 
-  defp set_span_attributes(result) do
+  defp set_span_attributes(result, _extra_attrs) do
     result
   end
 

instrumentation/opentelemetry_tesla/test/middleware/opentelemetry_tesla_middleware_test.exs

@@ -125,6 +125,41 @@ defmodule Tesla.Middleware.OpenTelemetryTest do
       assert_receive {:span, span(name: "POST :my-high-cardinality-url", attributes: _attributes)}
     end
 
+    test "with extra attrs",
+         %{
+           bypass: bypass
+         } do
+      defmodule TestClient do
+        def get(client) do
+          params = [id: ~c"3"]
+
+          Tesla.get(client, "/users/:id", opts: [path_params: params])
+        end
+
+        def client(url) do
+          middleware = [
+            {Tesla.Middleware.BaseUrl, url},
+            {Tesla.Middleware.OpenTelemetry, extra_attrs: %{"peer.service" => "myservicename"}},
+            Tesla.Middleware.PathParams
+          ]
+
+          Tesla.client(middleware)
+        end
+      end
+
+      Bypass.expect_once(bypass, "GET", "/users/3", 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 attributes["peer.service"] == "myservicename"
+    end
+
     test "uses custom span name function when passed in middleware opts",
          %{
            bypass: bypass