Support setting node and distribution using environment vars (#1672)

README.md

@@ -164,6 +164,9 @@ The following environment variables configure Livebook:
   * LIVEBOOK_APP_SERVICE_URL - sets the application url to manage this
     Livebook instance within the cloud provider platform.
 
+  * LIVEBOOK_BASE_URL_PATH - sets the base url path the web application is served on.
+    Useful when deploying behind a reverse proxy.
+
   * LIVEBOOK_COOKIE - sets the cookie for running Livebook in a cluster.
     Defaults to a random string that is generated on boot.
 
@@ -175,6 +178,10 @@ The following environment variables configure Livebook:
     "standalone" (Elixir standalone), "attached:NODE:COOKIE" (Attached node)
     or "embedded" (Embedded). Defaults to "standalone".
 
+  * LIVEBOOK_DISTRIBUTION - sets the node distribution for running Livebook in a
+    cluster. Must be "name" (long names) or "sname" (short names). Note that this
+    sets RELEASE_DISTRIBUTION if present when creating a release. Defaults to "sname".
+
   * LIVEBOOK_FORCE_SSL_HOST - sets a host to redirect to if the request is not over HTTP.
     Note it does not apply when accessing Livebook via localhost. Defaults to nil.
 
@@ -192,8 +199,8 @@ The following environment variables configure Livebook:
   * LIVEBOOK_IP - sets the ip address to start the web application on.
     Must be a valid IPv4 or IPv6 address.
 
-  * LIVEBOOK_BASE_URL_PATH - sets the base url path the web application is served on.
-    Useful when deploying behind a reverse proxy.
+  * LIVEBOOK_NODE - sets the node name for running Livebook in a cluster. Note that
+    this sets RELEASE_NODE if present when creating a release.
 
   * LIVEBOOK_PASSWORD - sets a password that must be used to access Livebook.
     Must be at least 12 characters. Defaults to token authentication.
@@ -224,11 +231,6 @@ The following environment variables configure Livebook:
 
 <!-- Environment variables -->
 
-If running Livebook as a Docker image or an Elixir release, [the environment
-variables used by Elixir releases are also available](
-https://hexdocs.pm/mix/Mix.Tasks.Release.html#module-environment-variables).
-The notables ones are `RELEASE_NODE` and `RELEASE_DISTRIBUTION`.
-
 If running Livebook via the command line, run `livebook server --help` to see
 all CLI-specific options.
 

lib/livebook.ex

@@ -160,6 +160,10 @@ defmodule Livebook do
              Livebook.Config.cookie!("RELEASE_COOKIE") ||
              Livebook.Utils.random_cookie()
 
+    if node = Livebook.Config.node!("LIVEBOOK_NODE", "LIVEBOOK_DISTRIBUTION") do
+      config :livebook, :node, node
+    end
+
     if app_service_name = Livebook.Config.app_service_name!("LIVEBOOK_APP_SERVICE_NAME") do
       config :livebook, :app_service_name, app_service_name
 

lib/livebook/config.ex

@@ -291,6 +291,25 @@ defmodule Livebook.Config do
     end
   end
 
+  @doc """
+  Parses node and distribution type from env.
+  """
+  def node!(node_env, distribution_env) do
+    case {System.get_env(node_env), System.get_env(distribution_env, "sname")} do
+      {nil, _} ->
+        nil
+
+      {name, "name"} ->
+        {:longnames, String.to_atom(name)}
+
+      {sname, "sname"} ->
+        {:shortnames, String.to_atom(sname)}
+
+      {_, other} ->
+        abort!(~s(#{distribution_env} must be one of "name" or "sname", got "#{other}"))
+    end
+  end
+
   @doc """
   Parses and validates the password from env.
   """

mix.exs

@@ -131,7 +131,7 @@ defmodule Livebook.MixProject do
   defp releases do
     [
       livebook: [
-        include_executables_for: [:unix],
+        include_executables_for: [:unix, :windows],
         include_erts: false,
         rel_templates_path: "rel/server",
         steps: [:assemble, &remove_cookie/1]

rel/server/env.bat.eex

@@ -1,4 +1,6 @@
+if defined LIVEBOOK_NODE set RELEASE_NODE="!LIVEBOOK_NODE!"
 if not defined RELEASE_NODE set RELEASE_NODE=livebook_server
+if defined LIVEBOOK_DISTRIBUTION set RELEASE_DISTRIBUTION="!LIVEBOOK_DISTRIBUTION!"
 set RELEASE_MODE=interactive
 
 set cookie_path="!RELEASE_ROOT!\releases\COOKIE"

rel/server/env.sh.eex

@@ -1,4 +1,5 @@
-export RELEASE_NODE="${RELEASE_NODE:-livebook_server}"
+export RELEASE_NODE=${LIVEBOOK_NODE:-${RELEASE_NODE:-livebook_server}}
+export RELEASE_DISTRIBUTION=${LIVEBOOK_DISTRIBUTION:-${RELEASE_DISTRIBUTION:-sname}}
 export RELEASE_MODE=interactive
 
 cookie_path="${RELEASE_ROOT}/releases/COOKIE"

test/livebook/config_test.exs

@@ -0,0 +1,48 @@
+defmodule Livebook.ConfigTest do
+  use ExUnit.Case, async: true
+
+  alias Livebook.Config
+
+  describe "node!/1" do
+    test "parses longnames" do
+      with_env([TEST_LIVEBOOK_NODE: "test@::1", TEST_LIVEBOOK_DISTRIBUTION: "name"], fn ->
+        assert Config.node!("TEST_LIVEBOOK_NODE", "TEST_LIVEBOOK_DISTRIBUTION") ==
+                 {:longnames, :"test@::1"}
+      end)
+    end
+
+    test "parses shortnames" do
+      with_env([TEST_LIVEBOOK_NODE: "test", TEST_LIVEBOOK_DISTRIBUTION: "sname"], fn ->
+        assert Config.node!("TEST_LIVEBOOK_NODE", "TEST_LIVEBOOK_DISTRIBUTION") ==
+                 {:shortnames, :test}
+      end)
+    end
+
+    test "parses shortnames by default" do
+      with_env([TEST_LIVEBOOK_NODE: "test", TEST_LIVEBOOK_DISTRIBUTION: nil], fn ->
+        assert Config.node!("TEST_LIVEBOOK_NODE", "TEST_LIVEBOOK_DISTRIBUTION") ==
+                 {:shortnames, :test}
+      end)
+    end
+
+    test "returns nil if node is not set" do
+      with_env([TEST_LIVEBOOK_NODE: nil, TEST_LIVEBOOK_DISTRIBUTION: "name"], fn ->
+        assert Config.node!("TEST_LIVEBOOK_NODE", "TEST_LIVEBOOK_DISTRIBUTION") == nil
+      end)
+    end
+  end
+
+  defp with_env(env_vars, fun) do
+    existing =
+      Enum.map(env_vars, fn {env, _value} ->
+        {env, env |> to_string() |> System.get_env()}
+      end)
+
+    try do
+      System.put_env(env_vars)
+      fun.()
+    after
+      System.put_env(existing)
+    end
+  end
+end