Fix race condition in storage test (#2068)

lib/livebook/storage.ex

@@ -152,14 +152,6 @@ defmodule Livebook.Storage do
     Path.join([Livebook.Config.data_path(), "livebook_config.ets"])
   end
 
-  @doc """
-  Synchronously awaits for all prior changes to be processed.
-  """
-  @spec sync() :: :ok
-  def sync() do
-    GenServer.call(__MODULE__, :sync)
-  end
-
   @impl true
   def init(_opts) do
     # Make sure that this process does not terminate abruptly
@@ -172,11 +164,6 @@ defmodule Livebook.Storage do
     {:ok, %{table: table}}
   end
 
-  @impl true
-  def handle_call(:sync, _from, state) do
-    {:reply, :ok, state}
-  end
-
   @impl true
   def handle_call({:insert, namespace, entity_id, attributes}, _from, %{table: table} = state) do
     keys_to_delete = Enum.map(attributes, fn {key, _val} -> key end)
@@ -194,13 +181,11 @@ defmodule Livebook.Storage do
     {:reply, :ok, state, {:continue, :save_to_file}}
   end
 
-  @impl true
   def handle_call({:delete, namespace, entity_id}, _from, %{table: table} = state) do
     :ets.delete(table, {namespace, entity_id})
     {:reply, :ok, state, {:continue, :save_to_file}}
   end
 
-  @impl true
   def handle_call({:delete_key, namespace, entity_id, key}, _from, %{table: table} = state) do
     delete_keys(table, namespace, entity_id, [key])
     {:reply, :ok, state, {:continue, :save_to_file}}

test/livebook/storage_test.exs

@@ -105,16 +105,25 @@ defmodule Livebook.StorageTest do
 
   describe "persistence" do
     defp read_table_and_lookup(entity) do
-      :ok = Storage.sync()
+      Process.sleep(1)
 
       {:ok, tab} =
-        Storage.config_file_path()
-        |> String.to_charlist()
-        |> :ets.file2tab()
+        with {:error, _} <- read_table() do
+          # :ets.tab2file is asynchronous and may occasionally take
+          # longer, so we retry once
+          Process.sleep(100)
+          read_table()
+        end
 
       :ets.lookup(tab, {:persistence, entity})
     end
 
+    defp read_table() do
+      Storage.config_file_path()
+      |> String.to_charlist()
+      |> :ets.file2tab()
+    end
+
     test "insert triggers saving to file" do
       :ok = Storage.insert(:persistence, "insert", key: "val")