reliable queueing for thumbnail generation

lib/philomena/application.ex

@@ -22,7 +22,6 @@ defmodule Philomena.Application do
 
       # Starts a worker by calling: Philomena.Worker.start_link(arg)
       # {Philomena.Worker, arg},
-      Philomena.Servers.ImageProcessor,
       Philomena.Servers.UserLinkUpdater,
       Philomena.Servers.PicartoChannelUpdater,
       Philomena.Servers.PiczelChannelUpdater,

lib/philomena/images.ex

@@ -9,6 +9,7 @@ defmodule Philomena.Images do
   alias Philomena.Repo
 
   alias Philomena.Elasticsearch
+  alias Philomena.ThumbnailWorker
   alias Philomena.DuplicateReports.DuplicateReport
   alias Philomena.Images.Image
   alias Philomena.Images.Hider
@@ -97,10 +98,7 @@ defmodule Philomena.Images do
     |> Repo.isolated_transaction(:serializable)
     |> case do
       {:ok, %{image: image}} = result ->
-        spawn(fn ->
-          repair_image(image)
-        end)
-
+        repair_image(image)
         reindex_image(image)
         Tags.reindex_tags(image.added_tags)
         UserStatistics.inc_stat(attribution[:user], :uploads)
@@ -181,9 +179,12 @@ defmodule Philomena.Images do
     |> where(id: ^image.id)
     |> Repo.update_all(set: [thumbnails_generated: false, processed: false])
 
-    Philomena.Images.Thumbnailer.generate_thumbnails(image.id)
+    Exq.enqueue(Exq, queue(image.image_mime_type), ThumbnailWorker, [image.id])
   end
 
+  defp queue("video/webm"), do: "videos"
+  defp queue(_mime_type), do: "images"
+
   def update_file(%Image{} = image, attrs) do
     image =
       image

lib/philomena/servers/image_processor.ex

@@ -1,45 +0,0 @@
-defmodule Philomena.Servers.ImageProcessor do
-  use GenServer
-
-  def start_link(default) when is_list(default) do
-    GenServer.start_link(__MODULE__, default)
-  end
-
-  def cast(image_id) do
-    pid = Process.whereis(:processor)
-    GenServer.cast(pid, {:enqueue, image_id})
-  end
-
-  def call do
-    pid = Process.whereis(:processor)
-    GenServer.call(pid, :wait, :infinity)
-  end
-
-  @impl true
-  def init([]) do
-    Process.register(self(), :processor)
-    {:ok, []}
-  end
-
-  @impl true
-  def handle_cast({:enqueue, image_id}, []) do
-    # Ensure that tempfiles get cleaned up by reaping
-    # the process after it is done
-    Task.async(fn -> process(image_id) end)
-    |> Task.await(:infinity)
-
-    {:noreply, []}
-  end
-
-  defp process(image_id) do
-    Philomena.Images.Thumbnailer.generate_thumbnails(image_id)
-  rescue
-    _ ->
-      nil
-  end
-
-  @impl true
-  def handle_call(:wait, _from, []) do
-    {:reply, nil, []}
-  end
-end

lib/philomena/workers/thumbnail_worker.ex

@@ -0,0 +1,7 @@
+defmodule Philomena.ThumbnailWorker do
+  alias Philomena.Images.Thumbnailer
+
+  def perform(image_id) do
+    Thumbnailer.generate_thumbnails(image_id)
+  end
+end

lib/philomena_web/controllers/image/file_controller.ex

@@ -12,10 +12,7 @@ defmodule PhilomenaWeb.Image.FileController do
   def update(conn, %{"image" => image_params}) do
     case Images.update_file(conn.assigns.image, image_params) do
       {:ok, %{image: image}} ->
-        spawn(fn ->
-          Images.repair_image(image)
-        end)
-
+        Images.repair_image(image)
         Images.reindex_image(image)
 
         conn

lib/philomena_web/controllers/image/repair_controller.ex

@@ -8,12 +8,10 @@ defmodule PhilomenaWeb.Image.RepairController do
   plug :load_and_authorize_resource, model: Image, id_name: "image_id", persisted: true
 
   def create(conn, _params) do
-    spawn(fn ->
-      Images.repair_image(conn.assigns.image)
-    end)
+    Images.repair_image(conn.assigns.image)
 
     conn
-    |> put_flash(:info, "Repair job started.")
+    |> put_flash(:info, "Repair job enqueued.")
     |> redirect(to: Routes.image_path(conn, :show, conn.assigns.image))
   end
 end

priv/repo/seeds_development.exs

@@ -11,7 +11,6 @@
 # and so on) as they will fail if something goes wrong.
 
 alias Philomena.{Repo, Forums.Forum, Users.User}
-alias Philomena.Servers.ImageProcessor
 alias Philomena.Comments
 alias Philomena.Images
 alias Philomena.Topics
@@ -139,7 +138,4 @@ for resource <- resources["forum_posts"] do
   end
 end
 
-# Wait for processor to finish
-ImageProcessor.call()
-
 IO.puts "---- Done."