Rescue ArithmeticError in schedule_update_on_error

lib/ex_rss/feed.ex

@@ -101,9 +101,15 @@ defmodule ExRss.Feed do
  retries = Changeset.get_field(changeset, :retries)
 
  new_timeout =
- (:math.pow(1.5, retries) * @base_timeout)
- |> round
- |> min(@max_timeout)
+ try do
+ (:math.pow(1.5, retries) * @base_timeout)
+ |> round
+ |> min(@max_timeout)
+ rescue
+ # `:math.pow` throws an `ArithmeticError` once `retries` crosses a
+ # certain threshold.
+ ArithmeticError -> @max_timeout
+ end
 
  next_update_at =
  changeset

test/ex_rss/feed_test.exs

@@ -42,6 +42,18 @@ defmodule ExRss.FeedTest do
  assert Timex.compare(changeset.changes.next_update_at, @now) == 1
  end
 
+ test "schedule_update_on_error with retries that cause an ArithmeticError" do
+ changeset =
+ %Feed{retries: 2000, next_update_at: @now}
+ |> Changeset.change()
+ |> Feed.schedule_update_on_error(@now)
+
+ diff = Timex.diff(changeset.changes.next_update_at, @now, :seconds)
+
+ assert %{retries: 2001} = changeset.changes
+ assert diff == @max_timeout
+ end
+
  test "schedule_update has a maximum timeout" do
  changeset =
  %Feed{retries: 20, next_update_at: @now}