livebook: add systemd user service, test, and docs

Co-authored-by: Yt <[e-mail]>

nixos/doc/manual/release-notes/rl-2311.section.md

···
 
 - [LibreNMS](https://www.librenms.org), a auto-discovering PHP/MySQL/SNMP based network monitoring. Available as [services.librenms](#opt-services.librenms.enable).
 
+- [Livebook](https://livebook.dev/), an interactive notebook with support for Elixir, graphs, machine learning, and more.
+
 - [sitespeed-io](https://sitespeed.io), a tool that can generate metrics (timings, diagnostics) for websites. Available as [services.sitespeed-io](#opt-services.sitespeed-io.enable).
 
 - [stalwart-mail](https://stalw.art), an all-in-one email server (SMTP, IMAP, JMAP). Available as [services.stalwart-mail](#opt-services.stalwart-mail.enable).

nixos/modules/module-list.nix

···
   ./services/development/hoogle.nix
   ./services/development/jupyter/default.nix
   ./services/development/jupyterhub/default.nix
+  ./services/development/livebook.nix
   ./services/development/lorri.nix
   ./services/development/rstudio-server/default.nix
   ./services/development/zammad.nix

nixos/modules/services/development/livebook.md

···
+# Livebook {#module-services-livebook}
+
+[Livebook](https://livebook.dev/) is a web application for writing
+interactive and collaborative code notebooks.
+
+## Basic Usage {#module-services-livebook-basic-usage}
+
+Enabling the `livebook` service creates a user
+[`systemd`](https://www.freedesktop.org/wiki/Software/systemd/) unit
+which runs the server.
+
+```
+{ ... }:
+
+{
+  services.livebook = {
+    enableUserService = true;
+    port = 20123;
+    # See note below about security
+    environmentFile = pkgs.writeText "livebook.env" ''
+      LIVEBOOK_PASSWORD = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
+    '';
+  };
+}
+```
+
+::: {.note}
+
+The Livebook server has the ability to run any command as the user it
+is running under, so securing access to it with a password is highly
+recommended.
+
+Putting the password in the Nix configuration like above is an easy
+way to get started but it is not recommended in the real world because
+the `livebook.env` file will be added to the world-readable Nix store.
+A better approach would be to put the password in some secure
+user-readable location and set `environmentFile = /home/user/secure/livebook.env`.
+
+:::

nixos/modules/services/development/livebook.nix

···
+{ config, lib, pkgs, ... }:
+
+with lib;
+let
+  cfg = config.services.livebook;
+in
+{
+  options.services.livebook = {
+    # Since livebook doesn't have a granular permission system (a user
+    # either has access to all the data or none at all), the decision
+    # was made to run this as a user service.  If that changes in the
+    # future, this can be changed to a system service.
+    enableUserService = mkEnableOption "a user service for Livebook";
+
+    environmentFile = mkOption {
+      type = types.path;
+      description = lib.mdDoc ''
+        Environment file as defined in {manpage}`systemd.exec(5)` passed to the service.
+
+        This must contain at least `LIVEBOOK_PASSWORD` or
+        `LIVEBOOK_TOKEN_ENABLED=false`.  See `livebook server --help`
+        for other options.'';
+    };
+
+    erlang_node_short_name = mkOption {
+      type = with types; nullOr str;
+      default = null;
+      example = "livebook";
+      description = "A short name for the distributed node.";
+    };
+
+    erlang_node_name = mkOption {
+      type = with types; nullOr str;
+      default = null;
+      example = "livebook@127.0.0.1";
+      description = "The name for the app distributed node.";
+    };
+
+    port = mkOption {
+      type = types.port;
+      default = 8080;
+      description = "The port to start the web application on.";
+    };
+
+    address = mkOption {
+      type = types.str;
+      default = "127.0.0.1";
+      description = lib.mdDoc ''
+        The address to start the web application on.  Must be a valid IPv4 or
+        IPv6 address.
+      '';
+    };
+
+    options = mkOption {
+      type = with types; attrsOf str;
+      default = { };
+      description = lib.mdDoc ''
+        Additional options to pass as command-line arguments to the server.
+      '';
+      example = literalExpression ''
+        {
+          cookie = "a value shared by all nodes in this cluster";
+        }
+      '';
+    };
+  };
+
+  config = mkIf cfg.enableUserService {
+    systemd.user.services.livebook = {
+      serviceConfig = {
+        Restart = "always";
+        EnvironmentFile = cfg.environmentFile;
+        ExecStart =
+          let
+            args = lib.cli.toGNUCommandLineShell { } ({
+              inherit (cfg) port;
+              ip = cfg.address;
+              name = cfg.erlang_node_name;
+              sname = cfg.erlang_node_short_name;
+            } // cfg.options);
+          in
+          "${pkgs.livebook}/bin/livebook server ${args}";
+      };
+      path = [ pkgs.bash ];
+      wantedBy = [ "default.target" ];
+    };
+  };
+
+  meta.doc = ./livebook.md;
+}

nixos/tests/all-tests.nix

···
   honk = runTest ./honk.nix;
   installed-tests = pkgs.recurseIntoAttrs (handleTest ./installed-tests {});
   invidious = handleTest ./invidious.nix {};
+  livebook-service = handleTest ./livebook-service.nix {};
   oci-containers = handleTestOn ["aarch64-linux" "x86_64-linux"] ./oci-containers.nix {};
   odoo = handleTest ./odoo.nix {};
   odoo15 = handleTest ./odoo.nix { package = pkgs.odoo15; };

nixos/tests/livebook-service.nix

···
+import ./make-test-python.nix ({ lib, pkgs, ... }: {
+  name = "livebook-service";
+
+  nodes = {
+    machine = { config, pkgs, ... }: {
+      imports = [
+        ./common/user-account.nix
+      ];
+
+      services.livebook = {
+        enableUserService = true;
+        port = 20123;
+        environmentFile = pkgs.writeText "livebook.env" ''
+          LIVEBOOK_PASSWORD = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
+        '';
+        options = {
+          cookie = "chocolate chip";
+        };
+      };
+    };
+  };
+
+  testScript = { nodes, ... }:
+    let
+      user = nodes.machine.config.users.users.alice;
+      sudo = lib.concatStringsSep " " [
+        "XDG_RUNTIME_DIR=/run/user/${toString user.uid}"
+        "sudo"
+        "--preserve-env=XDG_RUNTIME_DIR"
+        "-u"
+        "alice"
+      ];
+    in
+    ''
+      machine.wait_for_unit("multi-user.target")
+
+      machine.succeed("loginctl enable-linger alice")
+      machine.wait_until_succeeds("${sudo} systemctl --user is-active livebook.service")
+      machine.wait_for_open_port(20123)
+
+      machine.succeed("curl -L localhost:20123 | grep 'Type password'")
+    '';
+})

pkgs/servers/web-apps/livebook/default.nix

···
-{ lib, beamPackages, makeWrapper, rebar3, elixir, erlang, fetchFromGitHub }:
+{ lib, beamPackages, makeWrapper, rebar3, elixir, erlang, fetchFromGitHub, nixosTests }:
 beamPackages.mixRelease rec {
   pname = "livebook";
   version = "0.11.3";
···
       --prefix PATH : ${lib.makeBinPath [ elixir ]} \
       --set MIX_REBAR3 ${rebar3}/bin/rebar3
   '';
+
+  passthru.tests = {
+    livebook-service = nixosTests.livebook-service;
+  };
 
   meta = with lib; {
     license = licenses.asl20;