Implement retries

apps/explorer/lib/explorer/buffered_task.ex

@@ -8,7 +8,7 @@ defmodule Explorer.BufferedTask do
   @callback init(initial :: term, reducer :: function) ::
               {:ok, accumulated_results :: term | initial :: term} | {:error, reason :: term}
 
-  @callback run(entries :: list) :: :ok | {:retry, reason :: term} | {:halt, reason :: term}
+  @callback run(entries :: list, retries :: pos_integer) :: :ok | {:retry, reason :: term} | {:halt, reason :: term}
 
   @flush_interval :timer.seconds(3)
 
@@ -83,11 +83,11 @@ defmodule Explorer.BufferedTask do
   end
 
   defp drop_task_and_retry(state, ref) do
-    batch = Map.fetch!(state.tasks, ref)
+    {batch, retries} = Map.fetch!(state.tasks, ref)
 
     state
     |> drop_task(ref)
-    |> buffer_entries(batch)
+    |> queue(batch, retries + 1)
   end
 
   defp buffer_entries(state, []), do: state
@@ -97,12 +97,16 @@ defmodule Explorer.BufferedTask do
     {batch, overflow} = Enum.split(current_buffer, state.max_batch_size)
 
     if length(batch) == state.max_batch_size do
-      %{state | current_buffer: overflow, buffer: :queue.in(batch, state.buffer)}
+      queue(%{state | current_buffer: overflow}, batch, 0)
     else
       %{state | current_buffer: current_buffer}
     end
   end
 
+  defp queue(state, batch, retries) do
+    %{state | buffer: :queue.in({batch, retries}, state.buffer)}
+  end
+
   defp do_initial_stream(state) do
     {0, []}
     |> state.callback_module.init(fn entry, {len, acc} ->
@@ -130,7 +134,7 @@ defmodule Explorer.BufferedTask do
   defp take_batch(state) do
     case :queue.out(state.buffer) do
       {{:value, batch}, new_queue} -> {batch, new_queue}
-      {:empty, new_queue} -> {:halt, {[], new_queue}}
+      {:empty, new_queue} -> {[], new_queue}
     end
   end
 
@@ -147,15 +151,15 @@ defmodule Explorer.BufferedTask do
     state = buffer_entries(state, entries)
 
     if Enum.count(state.tasks) < state.max_concurrency and :queue.len(state.buffer) > 0 do
-      {batch, new_queue} = take_batch(state)
+      {{batch, retries}, new_queue} = take_batch(state)
 
       task =
         Task.Supervisor.async_nolink(Explorer.TaskSupervisor, fn ->
           debug(state, fn -> "processing #{Enum.count(batch)} entries for #{inspect(state.callback_module)}" end)
-          {:performed, state.callback_module.run(batch)}
+          {:performed, state.callback_module.run(batch, retries)}
         end)
 
-      %{state | tasks: Map.put(state.tasks, task.ref, batch), buffer: new_queue}
+      %{state | tasks: Map.put(state.tasks, task.ref, {batch, retries}), buffer: new_queue}
     else
       state
     end
@@ -168,11 +172,9 @@ defmodule Explorer.BufferedTask do
   defp flush(%{current_buffer: current} = state) do
     {batch, overflow} = Enum.split(current, state.max_batch_size)
 
-    flush(%{
-      state
-      | buffer: :queue.in(batch, state.buffer),
-        current_buffer: overflow
-    })
+    %{state | current_buffer: overflow}
+    |> queue(batch, 0)
+    |> flush()
   end
 
   defp debug(%{debug_logs: true}, func), do: Logger.debug(func)

apps/explorer/lib/explorer/indexer/address_balance_fetcher.ex

@@ -19,7 +19,7 @@ defmodule Explorer.Indexer.AddressBalanceFetcher do
     end)
   end
 
-  def run(string_hashes) do
+  def run(string_hashes, _retries) do
     {:ok, results} = EthereumJSONRPC.fetch_balances_by_hash(string_hashes)
     :ok = Chain.update_balances(results)
 

apps/explorer/lib/explorer/indexer/internal_transaction_fetcher.ex

@@ -23,7 +23,7 @@ defmodule Explorer.Indexer.InternalTransactionFetcher do
     end)
   end
 
-  def run(transaction_hashes) do
+  def run(transaction_hashes, _retries) do
     case EthereumJSONRPC.fetch_internal_transactions(transaction_hashes) do
       {:ok, internal_params} ->
         {:ok, _} = Chain.import_internal_transactions(internal_params)

apps/explorer/test/explorer/buffered_task_test.exs

@@ -20,27 +20,49 @@ defmodule Explorer.BufferedTaskTest do
       {:ok, Enum.reduce(initial_collection(), acc, fn item, acc -> reducer.(item, acc) end)}
     end
 
-    def run(batch) do
+    def run(batch, 0) do
       send(__MODULE__, {:run, batch})
       :ok
     end
   end
 
-  defmodule FunTask do
+  defmodule EmptyTask do
     @behaviour BufferedTask
 
     def init(acc, _reducer) do
       {:ok, acc}
     end
 
-    def run([agent, func]) when is_function(func) do
-      count = Agent.get_and_update(agent, &{&1, &1 + 1})
-      send(__MODULE__, {:run, count})
-      func.(count)
+    def run(batch, 0) do
+      send(__MODULE__, {:run, batch})
+      :ok
+    end
   end
 
-    def run(batch) do
-      send(__MODULE__, {:run, batch})
+  defmodule RetryableTask do
+    @behaviour BufferedTask
+
+    def init(acc, _reducer) do
+      {:ok, acc}
+    end
+
+    def run([:boom], 0) do
+      send(__MODULE__, {:run, {0, :boom}})
+      raise "boom"
+    end
+
+    def run([:boom], 1) do
+      send(__MODULE__, {:run, {1, :boom}})
+      :ok
+    end
+
+    def run(batch, retries) when retries < 2 do
+      send(__MODULE__, {:run, {retries, batch}})
+      {:retry, :because_reasons}
+    end
+
+    def run(batch, retries) do
+      send(__MODULE__, {:final_run, {retries, batch}})
       :ok
     end
   end
@@ -69,8 +91,8 @@ defmodule Explorer.BufferedTaskTest do
   end
 
   test "init with zero entries schedules future buffer flushes" do
-    Process.register(self(), FunTask)
-    {:ok, buffer} = start_buffer(FunTask)
+    Process.register(self(), EmptyTask)
+    {:ok, buffer} = start_buffer(EmptyTask)
     refute_receive _
 
     BufferedTask.buffer(buffer, ~w(some more entries))
@@ -80,23 +102,28 @@ defmodule Explorer.BufferedTaskTest do
     refute_receive _
   end
 
+  @tag :capture_log
+  test "crashed runs are retried" do
+    Process.register(self(), RetryableTask)
+    {:ok, buffer} = start_buffer(RetryableTask)
+
+    BufferedTask.buffer(buffer, [:boom])
+    assert_receive {:run, {0, :boom}}
+    assert_receive {:run, {1, :boom}}
+    refute_receive _
+  end
+
   test "run/1 allows tasks to be programmatically retried" do
-    Process.register(self(), FunTask)
-    {:ok, buffer} = start_buffer(FunTask)
-    {:ok, count} = Agent.start_link(fn -> 1 end)
-
-    BufferedTask.buffer(buffer, [
-      count,
-      fn
-        1 -> {:retry, :because_reasons}
-        2 -> {:retry, :because_reasons}
-        3 -> :ok
-      end
-    ])
-
-    assert_receive {:run, 1}
-    assert_receive {:run, 2}
-    assert_receive {:run, 3}
+    Process.register(self(), RetryableTask)
+    {:ok, buffer} = start_buffer(RetryableTask)
+
+    BufferedTask.buffer(buffer, [1, 2, 3])
+    assert_receive {:run, {0, [1, 2]}}
+    assert_receive {:run, {0, [3]}}
+    assert_receive {:run, {1, [1, 2]}}
+    assert_receive {:run, {1, [3]}}
+    assert_receive {:final_run, {2, [1, 2]}}
+    assert_receive {:final_run, {2, [3]}}
     refute_receive _
   end
 end