Merge pull request #141 from alexcastano/master

Add custom retry time delay

README.md

@@ -87,6 +87,28 @@ This job can also be scheduled using `Verk.schedule/2`:
  Verk.schedule(%Verk.Job{queue: :default, class: "ExampleWorker", args: [1,2]}, perform_at)
  ```
 
+### Retry at
+
+A job can define the function `retry_at/2` for custom retry time delay:
+
+```elixir
+defmodule ExampleWorker do
+  def perform(arg1, arg2) do
+    arg1 + arg2
+  end
+
+  def retry_at(failed_at, retry_count) do
+    failed_at + retry_count
+  end
+end
+```
+
+In this example, the first retry will be scheduled a second later,
+the second retry will be scheduled two seconds later, and so on.
+
+If `retry_at/2` is not defined the default exponential backoff is used.
+
+
 ## Configuration
 
 Example configuration for verk having 2 queues: `default` and `priority`

lib/verk/retry_set.ex

@@ -17,7 +17,7 @@ defmodule Verk.RetrySet do
   """
   @spec add(%Job{}, integer,  GenServer.server) :: :ok | {:error, Redix.Error.t}
   def add(job, failed_at, redis \\ Verk.Redis) do
-    retry_at = calculate_retry_at(failed_at, job.retry_count)
+    retry_at = calculate_retry_at(job.class, failed_at, job.retry_count)
     case Redix.command(redis, ["ZADD", @retry_key, to_string(retry_at), Poison.encode!(job)]) do
       {:ok, _} -> :ok
       {:error, error} -> {:error, error}
@@ -34,7 +34,16 @@ defmodule Verk.RetrySet do
     bangify(add(job, failed_at, redis))
   end
 
-  defp calculate_retry_at(failed_at, retry_count) do
+  defp calculate_retry_at(module_name, failed_at, retry_count) do
+    module = Module.safe_concat([module_name])
+    if :erlang.function_exported(module, :retry_at, 2) do
+      apply(module, :retry_at, [failed_at, retry_count])
+    else
+      default_calculate_retry_at(failed_at, retry_count)
+    end
+  end
+
+  defp default_calculate_retry_at(failed_at, retry_count) do
     delay = :math.pow(retry_count, 4) + 15 + (:rand.uniform(30) * (retry_count + 1))
     failed_at + delay
   end

test/retry_set_test.exs

@@ -4,6 +4,12 @@ defmodule Verk.RetrySetTest do
   import Verk.RetrySet
   import :meck
 
+  defmodule DummyJob do
+    def retry_at(_failed_at, _retry_count) do
+      4
+    end
+  end
+
   setup do
     new [SortedSet, Redix]
     :rand.seed(:exs1024, {123, 123534, 345345})
@@ -23,6 +29,18 @@ defmodule Verk.RetrySetTest do
 
       assert validate [Poison, Redix]
     end
+
+    test "allows custom retry_at" do
+      job = %Verk.Job{ class: "Verk.RetrySetTest.DummyJob", retry_count: 1 }
+      failed_at = 1
+      retry_at  = "4"
+      expect(Poison, :encode!, [job], :payload)
+      expect(Redix, :command, [:redis, ["ZADD", "retry", retry_at, :payload]], { :ok, 1 })
+
+      assert add(job, failed_at, :redis) == :ok
+
+      assert validate [Poison, Redix]
+    end
   end
 
   describe "add!/3" do