retry write file

lib/feed_reader/collector.ex

@@ -126,11 +126,14 @@ defmodule FeedReader.Collector do
     path =
       Path.join(System.tmp_dir!(), "feed_reader-parse-#{System.unique_integer([:positive])}.xml")
 
-    case File.open(path, [:write, :binary]) do
+    case File.open(path, [:write, :binary, :exclusive]) do
       {:ok, file} ->
         File.close(file)
         {:ok, path}
 
+      {:error, :eexist} ->
+        temporary_path()
+
       {:error, reason} ->
         {:error, reason}
     end

lib/feed_reader/downloader.ex

@@ -228,7 +228,11 @@ defmodule FeedReader.Downloader do
     end)
   end
 
-  defp open_temp_file do
+  defp open_temp_file(attempts \\ 5)
+
+  defp open_temp_file(0), do: {:error, :eexist}
+
+  defp open_temp_file(attempts) do
     path =
       Path.join(
         System.tmp_dir!(),
@@ -237,6 +241,7 @@ defmodule FeedReader.Downloader do
 
     case File.open(path, [:write, :binary, :exclusive]) do
       {:ok, file} -> {:ok, path, file}
+      {:error, :eexist} -> open_temp_file(attempts - 1)
       error -> error
     end
   end