Start tracking which store paths are in use

This will enable garbage collection of the Guix store, without
removing things that are still in use.

2 files changed, 64 insertions, 0 deletions

diff --git a/app/services/govuk_guix/build_mini_environment.rb b/app/services/govuk_guix/build_mini_environment.rb
index 01920eb..9cada20 100644
--- a/app/services/govuk_guix/build_mini_environment.rb
+++ b/app/services/govuk_guix/build_mini_environment.rb
@@ -83,6 +83,8 @@ module GovukGuix::BuildMiniEnvironment
         build_output: build_output
       }
     )
+
+    build_output
   end
 
   def self.signon_user_to_sexp(signon_user)
diff --git a/app/services/govuk_guix/update_gcroots_directory.rb b/app/services/govuk_guix/update_gcroots_directory.rb
new file mode 100644
index 0000000..97fe703
--- /dev/null
+++ b/app/services/govuk_guix/update_gcroots_directory.rb
@@ -0,0 +1,62 @@
+# GOV.UK Mini Environment Admin
+# Copyright © 2018  Christopher Baines <mail@cbaines.net>
+#
+# This file is part of the GOV.UK Mini Environment Admin.
+#
+# The GOV.UK Mini Environment Admin is free software: you can
+# redistribute it and/or modify it under the terms of the GNU Affero
+# General Public License as published by the Free Software Foundation,
+# either version 3 of the License, or (at your option) any later
+# version.
+#
+# The GOV.UK Mini Environment Admin is distributed in the hope that it
+# will be useful, but WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public
+# License along with the GOV.UK Mini Environment Admin.  If not, see
+# <http://www.gnu.org/licenses/>.
+
+module GovukGuix::UpdateGcrootsDirectory
+  extend ::ShellUtils
+
+  DIRECTORY = '/var/guix/gcroots/govuk-mini-environment-admin'
+
+  def self.set_in_use_store_paths(store_paths, options = {})
+    current_store_paths = list_store_paths(options)
+
+    (current_store_paths - store_paths).each do |store_path|
+      remove_store_path(store_path, options)
+    end
+
+    (store_paths - current_store_paths).each do |store_path|
+      add_store_path(store_path, options)
+    end
+  end
+
+  def self.add_store_path(store_path, options = {})
+    run_command(
+      'ln', '-s',
+      store_path,
+      File.join(DIRECTORY, store_path['/gnu/store/'.length..-1]),
+      run_remotely_on_host: options[:run_remotely_on_host]
+    )
+  end
+
+  def self.remove_store_path(store_path, options = {})
+    run_command(
+      'rm', File.join(DIRECTORY, store_path['/gnu/store/'.length..-1]),
+      run_remotely_on_host: options[:run_remotely_on_host]
+    )
+  end
+
+  def self.list_store_paths(options = {})
+    run_command(
+      'ls', '-1', DIRECTORY,
+      run_remotely_on_host: options[:run_remotely_on_host]
+    ).map do |store_path_suffix|
+      "/gnu/store/#{store_path_suffix.strip}"
+    end
+  end
+end