Customize the Logger metadata key name

lib/plug/request_id.ex

@@ -47,6 +47,12 @@ defmodule Plug.RequestId do
 
           plug Plug.RequestId, assign_as: :plug_request_id
 
+    * `:log_as` - The name of the key that will be used to store the
+      discovered or generated request id in `Logger` metadata. If not provided,
+      the request id will be stored as `:request_id`.
+
+          plug Plug.RequestId, log_as: :my_request_id
+
   """
 
   require Logger
@@ -57,15 +63,16 @@ defmodule Plug.RequestId do
   def init(opts) do
     {
       Keyword.get(opts, :http_header, "x-request-id"),
-      Keyword.get(opts, :assign_as)
+      Keyword.get(opts, :assign_as),
+      Keyword.get(opts, :log_as, :request_id)
     }
   end
 
   @impl true
-  def call(conn, {header, assign_as}) do
+  def call(conn, {header, assign_as, log_as}) do
     request_id = get_request_id(conn, header)
 
-    Logger.metadata(request_id: request_id)
+    Logger.metadata([{log_as, request_id}])
     conn = if assign_as, do: Conn.assign(conn, assign_as, request_id), else: conn
 
     Conn.put_resp_header(conn, header, request_id)

test/plug/request_id_test.exs

@@ -82,6 +82,20 @@ defmodule Plug.RequestIdTest do
     assert res_request_id == meta_request_id
   end
 
+  test "adds the request id to Logger metadata with the given log key" do
+    request_id = "existingidthatislongenough"
+
+    conn =
+      conn(:get, "/")
+      |> put_req_header("x-request-id", request_id)
+      |> call(log_as: :plug_request_id)
+
+    [res_request_id] = get_resp_header(conn, "x-request-id")
+    meta_request_id = Logger.metadata()[:plug_request_id]
+    assert generated_request_id?(res_request_id)
+    assert res_request_id == meta_request_id
+  end
+
   defp generated_request_id?(request_id) do
     Regex.match?(~r/\A[A-Za-z0-9-_]+\z/, request_id)
   end