New way to deploy Ruby on Rails applications

If you set the `deployedExternally' option to true you can use the
nix-copy-closure command to deploy updates to the application.

See `scripts/deploy-rails-app.sh' for more details.

modules/services/web/rails/default.nix

@@ -25,7 +25,7 @@ let
     "${app.domain}" = {
       forceSSL = config.phoebe.security.enable;
       enableACME = config.phoebe.security.enable;
-      root = "${app.package}/share/${app.name}/public";
+      root = "${funcs.appLink app}/share/${app.name}/public";
 
       locations = {
         "/assets/" = {

modules/services/web/rails/functions.nix

@@ -10,6 +10,10 @@ rec {
   # Where a Rails application lives:
   home = name: "${base}/${name}";
 
+  ##############################################################################
+  # Path to where the app is actually installed:
+  appLink = app: "${app.home}/package";
+
   ##############################################################################
   # Is PostgreSQL local?
   localpg = config.phoebe.services.postgresql.enable;

modules/services/web/rails/options.nix

@@ -116,6 +116,21 @@ let
         '';
       };
 
+      deployedExternally = mkOption {
+        type = types.bool;
+        default = false;
+        example = true;
+        description = ''
+          When true, system activation will not override the app link
+          in the home directory.  However, it will be created if missing.
+
+          This is useful if you want to deploy your Rails application
+          using some external tool.  In the Phoebe scripts directory
+          there is an example script for deploying with
+          nix-copy-closure.
+        '';
+      };
+
       home = mkOption {
         type = types.path;
         description = "The directory where the application is deployed to.";

modules/services/web/rails/systemd.nix

@@ -52,18 +52,22 @@ let
         app.afterServices;
 
       preStart = optionalString service.isMain ''
+        # Link the package into the application's home directory:
+        if [ ! -e "${funcs.appLink app}" ] || [ "${toString app.deployedExternally}" -ne 1 ]; then
+          ln -nfs "${app.package}" "${funcs.appLink app}"
+        fi
+
         # Prepare the config directory:
         rm -rf ${app.home}/config
         mkdir -p ${app.home}/{config,log,tmp,db,state}
-
-        cp -rf ${app.package}/share/${app.name}/config.dist/* ${app.home}/config/
-        cp ${app.package}/share/${app.name}/db/schema.rb.dist ${app.home}/db/schema.rb
+        cp -rf ${funcs.appLink app}/share/${app.name}/config.dist/* ${app.home}/config/
+        cp ${funcs.appLink app}/share/${app.name}/db/schema.rb.dist ${app.home}/db/schema.rb
         cp ${./database.yml} ${app.home}/config/database.yml
         cp ${app.database.passwordFile} ${app.home}/state/database.password
 
         # Additional set up for the home directory:
         mkdir -p ${app.home}/home
-        ln -nfs ${app.package}/share/${app.name} ${app.home}/home/app
+        ln -nfs ${funcs.appLink app}/share/${app.name} ${app.home}/home/app
         ln -nfs ${plib.attrsToShellExports "rails-${app.name}-env" (funcs.appEnv app)} ${app.home}/home/.env
         cp ${./profile.sh} ${app.home}/home/.profile
         chmod 0700 ${app.home}/home/.profile
@@ -82,7 +86,7 @@ let
         # Migrate the database:
         ${pkgs.sudo}/bin/sudo --user=rails-${app.name} --login \
           ${scripts.user}/bin/db-migrate.sh \
-            -r ${app.package}/share/${app.name} \
+            -r ${funcs.appLink app}/share/${app.name} \
             -s ${app.home}/state
       '';
 
@@ -92,7 +96,7 @@ let
       '';
 
       serviceConfig = {
-        WorkingDirectory = "${app.package}/share/${app.name}";
+        WorkingDirectory = "-${funcs.appLink app}/share/${app.name}";
         Restart = "on-failure";
         TimeoutSec = "infinity"; # FIXME: what's a reasonable amount of time?
         Type = "simple";

scripts/deploy-rails-app.sh

@@ -0,0 +1,87 @@
+#!/bin/sh
+
+################################################################################
+# Example script to deploy a rails application:
+set -e
+set -u
+
+################################################################################
+option_base="/var/lib/rails"
+option_app_name=""
+option_host=""
+
+################################################################################
+usage() {
+  cat <<EOF
+Usage: $(basename "$0") -n <name> -t <host> [options]
+
+  -h      This message
+  -n NAME Application name
+  -p PATH Base path of Rails application (default: $option_base)
+  -t HOST SSH host to deploy to (e.g., root@example.com)
+EOF
+}
+
+################################################################################
+while getopts "hn:p:t:" o; do
+  case "${o}" in
+    h) usage
+       exit
+       ;;
+
+    n) option_app_name=$OPTARG
+       ;;
+
+    p) option_base=$OPTARG
+       ;;
+
+    t) option_host=$OPTARG
+       ;;
+
+    *) exit 1
+       ;;
+  esac
+done
+
+shift $((OPTIND-1))
+
+################################################################################
+if [ ! -e default.nix ]; then
+  >&2 echo "ERROR: Run this from a directory that has a default.nix file"
+  exit 1
+fi
+
+################################################################################
+if [ -z "$option_app_name" ]; then
+  >&2 echo "ERROR: You must use the -n option to name the application"
+  exit 1
+fi
+
+################################################################################
+if [ -z "$option_host" ]; then
+  >&2 echo "ERROR: You must use the -t option to specify the host"
+  exit 1
+fi
+
+################################################################################
+if [ $# -ne 0 ]; then
+  >&2 echo "ERROR: invalid options given: $*"
+  exit 1
+fi
+
+################################################################################
+echo "==> Building application"
+path=$(nix-build --quiet --no-out-link)
+
+echo "==> Uploading application to $option_host"
+nix-copy-closure --use-substitutes --to "$option_host" "$path"
+
+# Create the GC root:
+echo "==> Installing and activating application"
+ssh "$option_host" \
+    nix-store --add-root "$option_base/$option_app_name/package" \
+              --indirect --realize --quiet "$path"
+
+# Restart the application:
+echo "==> Restarting application"
+ssh "$option_host" systemctl restart rails-"$option_app_name"-'\*'