test/build: Stability, compatibility

lib/parrhesia/storage/adapters/memory/store.ex

@@ -22,7 +22,17 @@ defmodule Parrhesia.Storage.Adapters.Memory.Store do
     audit_logs: []
   }
 
-  def ensure_started, do: start_store()
+  def start_link(opts \\ []) do
+    name = Keyword.get(opts, :name, @name)
+    Agent.start_link(&init_state/0, name: name)
+  end
+
+  def ensure_started do
+    case Process.whereis(@name) do
+      pid when is_pid(pid) -> :ok
+      nil -> start_store()
+    end
+  end
 
   def put_event(event_id, event) when is_binary(event_id) and is_map(event) do
     :ok = ensure_started()
@@ -159,28 +169,72 @@ defmodule Parrhesia.Storage.Adapters.Memory.Store do
   defp normalize_reduce_result(next_acc), do: next_acc
 
   def get(fun) do
-    :ok = ensure_started()
-    Agent.get(@name, fun)
+    with_store(fn pid -> Agent.get(pid, fun) end)
   end
 
   def update(fun) do
-    :ok = ensure_started()
-    Agent.update(@name, fun)
+    with_store(fn pid -> Agent.update(pid, fun) end)
   end
 
   def get_and_update(fun) do
-    :ok = ensure_started()
-    Agent.get_and_update(@name, fun)
+    with_store(fn pid -> Agent.get_and_update(pid, fun) end)
   end
 
   defp start_store do
-    case Agent.start_link(&init_state/0, name: @name) do
-      {:ok, _pid} -> :ok
-      {:error, {:already_started, _pid}} -> :ok
-      {:error, reason} -> {:error, reason}
+    case start_link() do
+      {:ok, _pid} ->
+        :ok
+
+      {:error, {:already_started, pid}} ->
+        if Process.alive?(pid) do
+          :ok
+        else
+          wait_for_store_exit(pid)
+        end
+
+      {:error, reason} ->
+        {:error, reason}
     end
   end
 
+  defp with_store(fun, attempts \\ 2)
+
+  defp with_store(fun, attempts) when attempts > 0 do
+    :ok = ensure_started()
+
+    case Process.whereis(@name) do
+      pid when is_pid(pid) ->
+        try do
+          fun.(pid)
+        catch
+          :exit, reason ->
+            if noproc_exit?(reason) and attempts > 1 do
+              with_store(fun, attempts - 1)
+            else
+              exit(reason)
+            end
+        end
+
+      nil ->
+        with_store(fun, attempts - 1)
+    end
+  end
+
+  defp with_store(_fun, 0), do: exit(:noproc)
+
+  defp wait_for_store_exit(pid) do
+    ref = Process.monitor(pid)
+
+    receive do
+      {:DOWN, ^ref, :process, ^pid, _reason} -> start_store()
+    after
+      100 -> start_store()
+    end
+  end
+
+  defp noproc_exit?({:noproc, _details}), do: true
+  defp noproc_exit?(_reason), do: false
+
   defp init_state do
     ensure_tables_started()
 

lib/parrhesia/storage/supervisor.ex

@@ -13,11 +13,19 @@ defmodule Parrhesia.Storage.Supervisor do
 
   @impl true
   def init(_init_arg) do
-    children = moderation_cache_children() ++ PostgresRepos.started_repos()
+    children =
+      memory_store_children() ++ moderation_cache_children() ++ PostgresRepos.started_repos()
 
     Supervisor.init(children, strategy: :one_for_one)
   end
 
+  defp memory_store_children do
+    case Application.get_env(:parrhesia, :storage, [])[:backend] do
+      :memory -> [Parrhesia.Storage.Adapters.Memory.Store]
+      _other -> []
+    end
+  end
+
   defp moderation_cache_children do
     if PostgresRepos.postgres_enabled?() and
          Application.get_env(:parrhesia, :moderation_cache_enabled, true) do