Stabilize preview and sandbox cleanup

lib/bds/desktop/shell_live/settings_editor/style_editor.ex

@@ -4,6 +4,7 @@ defmodule BDS.Desktop.ShellLive.SettingsEditor.StyleEditor do
   use Phoenix.Component
 
   alias BDS.Metadata
+  alias BDS.Preview
   use Gettext, backend: BDS.Gettext
 
   @themes [
@@ -42,7 +43,8 @@ defmodule BDS.Desktop.ShellLive.SettingsEditor.StyleEditor do
       applied_theme: current_theme(assigns),
       preview_mode: preview_mode,
       preview_url:
-        "http://127.0.0.1:4123/__style-preview?theme=#{selected_theme}&mode=#{preview_mode}"
+        Preview.base_url() <>
+          "/__style-preview?theme=#{selected_theme}&mode=#{preview_mode}"
     }
   end
 

lib/bds/preview.ex

@@ -12,12 +12,14 @@ defmodule BDS.Preview do
   alias BDS.Rendering.TemplateSelection
 
   @host "127.0.0.1"
-  @port 4123
+  @preferred_port 4123
   @server_table __MODULE__.ServerTable
 
   # Max time to wait for inflight requests to finish during graceful shutdown
   # before remaining request tasks are forcibly terminated.
   @drain_timeout 5_000
+  @listen_retry_attempts 10
+  @listen_retry_delay_ms 50
 
   def start_link(_opts) do
     GenServer.start_link(__MODULE__, %{}, name: __MODULE__)
@@ -41,7 +43,17 @@ defmodule BDS.Preview do
     )
   end
 
-  def base_url, do: "http://#{@host}:#{@port}"
+  def base_url do
+    case :ets.whereis(@server_table) do
+      :undefined -> "http://#{@host}:#{@preferred_port}"
+
+      _table ->
+        case :ets.lookup(@server_table, :current) do
+          [{:current, %{host: host, port: port}}] -> "http://#{host}:#{port}"
+          _other -> "http://#{@host}:#{@preferred_port}"
+        end
+    end
+  end
 
   def stop_preview(project_id) when is_binary(project_id) do
     GenServer.call(__MODULE__, {:stop_preview, project_id})
@@ -501,14 +513,7 @@ defmodule BDS.Preview do
     state = stop_current_server(state)
     maybe_allow_repo(owner_pid)
 
-    {:ok, listener} =
-      :gen_tcp.listen(@port, [
-        :binary,
-        packet: :raw,
-        active: false,
-        reuseaddr: true,
-        ip: {127, 0, 0, 1}
-      ])
+    {:ok, listener, port} = listen_with_retry(@listen_retry_attempts)
 
     acceptor_pid = spawn_link(fn -> accept_loop(listener, project_id, owner_pid) end)
 
@@ -516,7 +521,7 @@ defmodule BDS.Preview do
       project_id: project_id,
       data_dir: data_dir,
       host: @host,
-      port: @port,
+      port: port,
       is_running: true,
       owner_pid: owner_pid,
       listener: listener,
@@ -528,6 +533,40 @@ defmodule BDS.Preview do
     {{:ok, public_server(server)}, %{state | current: server}}
   end
 
+  defp listen_with_retry(attempts_left) when attempts_left > 0 do
+    case listen_on_port(@preferred_port) do
+      {:ok, listener, port} ->
+        {:ok, listener, port}
+
+      {:error, :eaddrinuse} when attempts_left > 1 ->
+        Process.sleep(@listen_retry_delay_ms)
+        listen_with_retry(attempts_left - 1)
+
+      {:error, :eaddrinuse} ->
+        listen_on_port(0)
+
+      {:error, reason} ->
+        {:error, reason}
+    end
+  end
+
+  defp listen_on_port(port) do
+    case :gen_tcp.listen(port, [
+           :binary,
+           packet: :raw,
+           active: false,
+           reuseaddr: true,
+           ip: {127, 0, 0, 1}
+         ]) do
+      {:ok, listener} ->
+        {:ok, {_host, actual_port}} = :inet.sockname(listener)
+        {:ok, listener, actual_port}
+
+      {:error, reason} ->
+        {:error, reason}
+    end
+  end
+
   defp run_tracked_request(fun) when is_function(fun, 0) do
     owner_pid = self()
 

lib/bds/projects.ex

@@ -12,6 +12,8 @@ defmodule BDS.Projects do
 
   @default_project_id "default"
   @default_project_name "My Blog"
+  @create_project_retry_attempts 5
+  @create_project_retry_delay_ms 50
 
   @typedoc "An attribute map that may use atom or string keys."
   @type attrs :: %{optional(atom()) => term(), optional(String.t()) => term()}
@@ -152,22 +154,24 @@ defmodule BDS.Projects do
     name = attr(attrs, :name) || ""
     slug = unique_slug(attr(attrs, :slug) || Slug.slugify(name))
 
-    Repo.transaction(fn ->
-      project =
-        %Project{}
-        |> Project.changeset(%{
-          id: Ecto.UUID.generate(),
-          name: name,
-          slug: slug,
-          description: attr(attrs, :description),
-          data_path: attr(attrs, :data_path),
-          created_at: now,
-          updated_at: now,
-          is_active: false
-        })
-        |> Repo.insert!()
+    retry_create_project(fn ->
+      Repo.transaction(fn ->
+        project =
+          %Project{}
+          |> Project.changeset(%{
+            id: Ecto.UUID.generate(),
+            name: name,
+            slug: slug,
+            description: attr(attrs, :description),
+            data_path: attr(attrs, :data_path),
+            created_at: now,
+            updated_at: now,
+            is_active: false
+          })
+          |> Repo.insert!()
 
-      project
+        project
+      end)
     end)
     |> case do
       {:ok, project} ->
@@ -182,6 +186,22 @@ defmodule BDS.Projects do
     end
   end
 
+  defp retry_create_project(fun, attempts_left \\ @create_project_retry_attempts)
+
+  defp retry_create_project(fun, attempts_left) when attempts_left > 1 do
+    fun.()
+  rescue
+    error in [Exqlite.Error] ->
+      if String.contains?(Exception.message(error), "Database busy") do
+        Process.sleep(@create_project_retry_delay_ms)
+        retry_create_project(fun, attempts_left - 1)
+      else
+        reraise error, __STACKTRACE__
+      end
+  end
+
+  defp retry_create_project(fun, _attempts_left), do: fun.()
+
   @spec set_active_project(String.t()) :: {:ok, Project.t()} | {:error, :not_found | term()}
   def set_active_project(project_id) do
     case Repo.get(Project, project_id) do