opentelemetry_req: Don't assume `request.headers` shape (#193)

* opentelemetry_req: Don't assume `request.headers` shape

* Update instrumentation/opentelemetry_req/test/opentelemetry_req_test.exs

---------

Co-authored-by: Bryan Naegele <bryannaegele@users.noreply.github.com>

instrumentation/opentelemetry_req/lib/opentelemetry_req.ex

@@ -202,7 +202,12 @@ defmodule OpentelemetryReq do
 
   defp maybe_put_trace_headers(request) do
     if request.options[:propagate_trace_ctx] do
-      Map.put(request, :headers, :otel_propagator_text_map.inject(request.headers))
+      propagator = :opentelemetry.get_text_map_injector()
+      headers_to_inject = :otel_propagator_text_map.inject(propagator, [], &[{&1, &2} | &3])
+
+      Enum.reduce(headers_to_inject, request, fn {name, value}, acc ->
+        Req.Request.put_header(acc, name, value)
+      end)
     else
       request
     end

instrumentation/opentelemetry_req/mix.exs

@@ -60,7 +60,8 @@ defmodule OpentelemetryReq.MixProject do
       {:opentelemetry_api, "~> 1.0"},
       {:opentelemetry_semantic_conventions, "~> 0.2"},
       {:req, ">= 0.3.5"},
-      {:ex_doc, "~> 0.29", only: [:dev, :test]}
+      {:ex_doc, "~> 0.29", only: [:dev, :test]},
+      {:opentelemetry, "~> 1.0", only: :test}
     ]
   end
 end

instrumentation/opentelemetry_req/mix.lock

@@ -13,6 +13,7 @@
   "nimble_options": {:hex, :nimble_options, "0.5.2", "42703307b924880f8c08d97719da7472673391905f528259915782bb346e0a1b", [:mix], [], "hexpm", "4da7f904b915fd71db549bcdc25f8d56f378ef7ae07dc1d372cbe72ba950dce0"},
   "nimble_parsec": {:hex, :nimble_parsec, "1.2.3", "244836e6e3f1200c7f30cb56733fd808744eca61fd182f731eac4af635cc6d0b", [:mix], [], "hexpm", "c8d789e39b9131acf7b99291e93dae60ab48ef14a7ee9d58c6964f59efb570b0"},
   "nimble_pool": {:hex, :nimble_pool, "0.2.6", "91f2f4c357da4c4a0a548286c84a3a28004f68f05609b4534526871a22053cde", [:mix], [], "hexpm", "1c715055095d3f2705c4e236c18b618420a35490da94149ff8b580a2144f653f"},
+  "opentelemetry": {:hex, :opentelemetry, "1.3.0", "988ac3c26acac9720a1d4fb8d9dc52e95b45ecfec2d5b5583276a09e8936bc5e", [:rebar3], [{:opentelemetry_api, "~> 1.2.0", [hex: :opentelemetry_api, repo: "hexpm", optional: false]}, {:opentelemetry_semantic_conventions, "~> 0.2", [hex: :opentelemetry_semantic_conventions, repo: "hexpm", optional: false]}], "hexpm", "8e09edc26aad11161509d7ecad854a3285d88580f93b63b0b1cf0bac332bfcc0"},
   "opentelemetry_api": {:hex, :opentelemetry_api, "1.2.1", "7b69ed4f40025c005de0b74fce8c0549625d59cb4df12d15c32fe6dc5076ff42", [:mix, :rebar3], [{:opentelemetry_semantic_conventions, "~> 0.2", [hex: :opentelemetry_semantic_conventions, repo: "hexpm", optional: false]}], "hexpm", "6d7a27b7cad2ad69a09cabf6670514cafcec717c8441beb5c96322bac3d05350"},
   "opentelemetry_semantic_conventions": {:hex, :opentelemetry_semantic_conventions, "0.2.0", "b67fe459c2938fcab341cb0951c44860c62347c005ace1b50f8402576f241435", [:mix, :rebar3], [], "hexpm", "d61fa1f5639ee8668d74b527e6806e0503efc55a42db7b5f39939d84c07d6895"},
   "req": {:hex, :req, "0.3.6", "541350d2cc359a8ad17059f2629c18be56d0c85ce0e4ddb27694b6ba482fe923", [:mix], [{:brotli, "~> 0.3.1", [hex: :brotli, repo: "hexpm", optional: true]}, {:ezstd, "~> 1.0", [hex: :ezstd, repo: "hexpm", optional: true]}, {:finch, "~> 0.9", [hex: :finch, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}, {:mime, "~> 1.6 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:nimble_csv, "~> 1.0", [hex: :nimble_csv, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: true]}], "hexpm", "9181047f32b05f8737f6b5917af5ee5385219158bbe4e507f4ec57791a0a78c3"},

instrumentation/opentelemetry_req/test/opentelemetry_req_test.exs

@@ -1,4 +1,64 @@
 defmodule OpentelemetryReqTest do
-  use ExUnit.Case
+  use ExUnit.Case, async: true
   doctest OpentelemetryReq
+  require Record
+
+  for {name, spec} <- Record.extract_all(from_lib: "opentelemetry/include/otel_span.hrl") do
+    Record.defrecordp(name, spec)
+  end
+
+  setup do
+    :application.stop(:opentelemetry)
+    :application.set_env(:opentelemetry, :tracer, :otel_tracer_default)
+
+    :application.set_env(:opentelemetry, :processors, [
+      {:otel_batch_processor, %{scheduled_delay_ms: 1, exporter: {:otel_exporter_pid, self()}}}
+    ])
+
+    :application.start(:opentelemetry)
+
+    req =
+      Req.new()
+      |> OpentelemetryReq.attach()
+
+    {:ok, req: req}
+  end
+
+  test "span", %{req: req} do
+    adapter = fn request ->
+      assert URI.to_string(request.url) == "/users/3"
+      {request, Req.Response.new(status: 204)}
+    end
+
+    resp =
+      Req.get!(req,
+        adapter: adapter,
+        url: "/users/:id",
+        path_params: [id: 3]
+      )
+
+    assert resp.status == 204
+    assert_receive {:span, span(name: "/users/:id")}
+    refute_receive _
+  end
+
+  test "propagate traces", %{req: req} do
+    adapter = fn request ->
+      assert [value] = Req.Request.get_header(request, "traceparent")
+      assert byte_size(value) > 10
+      {request, Req.Response.new(status: 204)}
+    end
+
+    resp =
+      Req.get!(req,
+        adapter: adapter,
+        url: "/",
+        no_path_params: true,
+        propagate_trace_ctx: true
+      )
+
+    assert resp.status == 204
+    assert_receive {:span, span()}
+    refute_receive _
+  end
 end