Allow LIVEBOOK_PORT to be set to 0 for a random port (#906)

README.md

@@ -169,7 +169,8 @@ The following environment variables configure Livebook:
 
   * LIVEBOOK_PORT - sets the port Livebook runs on. If you want to run multiple
     instances on the same domain with the same credentials but on different ports,
-    you also need to set LIVEBOOK_SECRET_KEY_BASE. Defaults to 8080.
+    you also need to set LIVEBOOK_SECRET_KEY_BASE. Defaults to 8080. If set to 0,
+    a random port will be picked.
 
   * LIVEBOOK_ROOT_PATH - sets the root path to use for file selection. This does
     not restrict access to upper directories unless the operating system user is

config/prod.exs

@@ -5,8 +5,8 @@ config :livebook, LivebookWeb.Endpoint,
   http: [ip: {127, 0, 0, 1}, port: 8080],
   server: true
 
-# Start log-level in notice by default to reduce output
-config :logger, level: :notice
+# Set log level to warning by default to reduce output
+config :logger, level: :warning
 
 # ## SSL Support
 #

lib/livebook/application.ex

@@ -27,7 +27,8 @@ defmodule Livebook.Application do
         # Start the unique task dependencies
         Livebook.UniqueTask,
         # Start the Endpoint (http/https)
-        LivebookWeb.Endpoint
+        # We skip the access url as we do our own logging below
+        {LivebookWeb.Endpoint, log_access_url: false}
       ] ++ app_specs()
 
     opts = [strategy: :one_for_one, name: Livebook.Supervisor]

lib/livebook_app.ex

@@ -78,10 +78,8 @@ if Mix.target() == :app do
     end
 
     defp import_livebook(url) do
-      %{
-        URI.parse(LivebookWeb.Endpoint.access_url())
-        | path: "/import"
-      }
+      LivebookWeb.Endpoint.access_struct_url()
+      |> Map.replace!(:path, "/import")
       |> append_query("url=#{URI.encode_www_form(url)}")
       |> URI.to_string()
       |> Livebook.Utils.browser_open()

lib/livebook_web/endpoint.ex

@@ -78,14 +78,41 @@ defmodule LivebookWeb.Endpoint do
 
   plug LivebookWeb.Router
 
-  def access_url() do
-    root_url = url()
+  def access_struct_url() do
+    base =
+      case struct_url() do
+        %URI{scheme: "https", port: 0} = uri ->
+          %{uri | port: get_port(__MODULE__.HTTPS, 433)}
+
+        %URI{scheme: "http", port: 0} = uri ->
+          %{uri | port: get_port(__MODULE__.HTTP, 80)}
+
+        %URI{} = uri ->
+          uri
+      end
+
+    base = update_in(base.path, &(&1 || "/"))
 
     if Livebook.Config.auth_mode() == :token do
       token = Application.fetch_env!(:livebook, :token)
-      root_url <> "/?token=" <> token
+      %{base | query: "token=" <> token}
     else
-      root_url
+      base
+    end
+  end
+
+  def access_url do
+    URI.to_string(access_struct_url())
+  end
+
+  defp get_port(ref, default) do
+    try do
+      :ranch.get_addr(ref)
+    rescue
+      _ -> default
+    else
+      {_, port} when is_integer(port) -> port
+      _ -> default
     end
   end
 end