Add LIVEBOOK_SHUTDOWN_ENABLED (#1111)

* Add LIVEBOOK_SHUTDOWN_ENABLED

Previously we relied on code:get_mode(), but since
releases are starting in interactive mode to use
less memory, we need a clearer mechanism.

* Move shutdown feature check to Livebook.Config

Co-authored-by: Jonatan Kłosko <jonatanklosko@gmail.com>

README.md

@@ -180,6 +180,9 @@ The following environment variables configure Livebook:
     long and it can be generated by commands such as: 'openssl rand -base64 48'.
     Defaults to a random secret on every boot.
 
+  * LIVEBOOK_SHUTDOWN_ENABLED - controls if a shutdown button should be shown
+    in the homepage. Set it to "true" to enable it.
+
   * LIVEBOOK_TOKEN_ENABLED - controls whether token authentication is enabled.
     Enabled by default unless `LIVEBOOK_PASSWORD` is set. Set it to "false" to
     disable it.

config/config.exs

@@ -19,15 +19,12 @@ config :mime, :types, %{
   "text/plain" => ["livemd"]
 }
 
-# Sets the default storage backend
-config :livebook, :storage, Livebook.Storage.Ets
-
-# Sets the default authentication mode to token
-config :livebook, :authentication_mode, :token
-
-config :livebook, :plugs, []
-
-config :livebook, :explore_notebooks, []
+config :livebook,
+  authentication_mode: :token,
+  explore_notebooks: [],
+  plugs: [],
+  shutdown_enabled: false,
+  storage: Livebook.Storage.Ets
 
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.

config/dev.exs

@@ -24,6 +24,7 @@ config :livebook, LivebookWeb.Endpoint,
   ]
 
 config :livebook, :iframe_port, 4001
+config :livebook, :shutdown_enabled, true
 
 # ## SSL Support
 #

lib/livebook.ex

@@ -102,7 +102,7 @@ defmodule Livebook do
       password = Livebook.Config.password!("LIVEBOOK_PASSWORD") ->
         config :livebook, authentication_mode: :password, password: password
 
-      Livebook.Config.token_enabled!("LIVEBOOK_TOKEN_ENABLED") ->
+      Livebook.Config.boolean!("LIVEBOOK_TOKEN_ENABLED", true) ->
         config :livebook, token: Livebook.Utils.random_id()
 
       true ->
@@ -113,6 +113,10 @@ defmodule Livebook do
       config :livebook, :iframe_port, port
     end
 
+    if Livebook.Config.boolean!("LIVEBOOK_SHUTDOWN_ENABLED", false) do
+      config :livebook, :shutdown_enabled, true
+    end
+
     config :livebook,
            :default_runtime,
            Livebook.Config.default_runtime!("LIVEBOOK_DEFAULT_RUNTIME") ||

lib/livebook/config.ex

@@ -98,6 +98,14 @@ defmodule Livebook.Config do
     end
   end
 
+  @doc """
+  Returns whether the shutdown feature is enabled.
+  """
+  @spec shutdown_enabled?() :: boolean()
+  def shutdown_enabled?() do
+    Application.fetch_env!(:livebook, :shutdown_enabled)
+  end
+
   ## Parsing
 
   @doc """
@@ -202,8 +210,11 @@ defmodule Livebook.Config do
   @doc """
   Parses token auth setting from env.
   """
-  def token_enabled!(env) do
-    System.get_env(env, "1") in ~w(true 1)
+  def boolean!(env, default \\ false) do
+    case System.get_env(env) do
+      nil -> default
+      var -> var in ~w(true 1)
+    end
   end
 
   @doc """

lib/livebook_web/live/sidebar_helpers.ex

@@ -58,7 +58,7 @@ defmodule LivebookWeb.SidebarHelpers do
   end
 
   def shutdown_item(assigns) do
-    if :code.get_mode() == :interactive do
+    if Livebook.Config.shutdown_enabled?() do
       ~H"""
       <span class="tooltip right distant" data-tooltip="Shutdown">
         <button class="text-2xl text-gray-400 hover:text-gray-50 focus:text-gray-50 rounded-xl h-10 w-10 flex items-center justify-center"
@@ -121,13 +121,17 @@ defmodule LivebookWeb.SidebarHelpers do
   end
 
   def shared_home_handlers(socket) do
-    attach_hook(socket, :shutdown, :handle_event, fn
-      "shutdown", _params, socket ->
-        System.stop()
-        {:halt, put_flash(socket, :info, "Livebook is shutting down. You can close this page.")}
+    if Livebook.Config.shutdown_enabled?() do
+      attach_hook(socket, :shutdown, :handle_event, fn
+        "shutdown", _params, socket ->
+          System.stop()
+          {:halt, put_flash(socket, :info, "Livebook is shutting down. You can close this page.")}
 
-      _event, _params, socket ->
-        {:cont, socket}
-    end)
+        _event, _params, socket ->
+          {:cont, socket}
+      end)
+    else
+      socket
+    end
   end
 end

rel/app/env.bat.eex

@@ -1,4 +1,5 @@
 set RELEASE_MODE=interactive
+set LIVEBOOK_SHUTDOWN_ENABLED=true
 
 set cookie_path="!RELEASE_ROOT!\releases\COOKIE"
 if not exist %cookie_path% (

rel/app/env.sh.eex

@@ -1,4 +1,5 @@
 export RELEASE_MODE=interactive
+export LIVEBOOK_SHUTDOWN_ENABLED=true
 
 cookie_path="${RELEASE_ROOT}/releases/COOKIE"
 if [ ! -f $cookie_path ]; then