1 files changed, 216 insertions, 0 deletions
diff --git a/home-manager/modules/systemd-activate.rb b/home-manager/modules/systemd-activate.rb
new file mode 100644
index 00000000000..31d06d8fc19
--- /dev/null
+++ b/home-manager/modules/systemd-activate.rb
@@ -0,0 +1,216 @@
+require 'set'
+require 'open3'
+
+@dry_run = ENV['DRY_RUN']
+@verbose = ENV['VERBOSE']
+
+UnitsDir = 'home-files/.config/systemd/user'
+
+# 1. Stop all services from the old generation that are not present in the new generation.
+# 2. Ensure all services from the new generation that are wanted by active targets are running:
+#    - Start services that are not already running.
+#    - Restart services whose unit config files have changed between generations.
+# 3. If any services were (re)started, wait 'start_timeout_ms' and report services
+#    that failed to start. This helps debugging quickly failing services.
+#
+# Whenever service failures are detected, show the output of
+# 'systemd --user status' for the affected services.
+#
+def setup_services(old_gen_path, new_gen_path, start_timeout_ms_string)
+  start_timeout_ms = start_timeout_ms_string.to_i
+
+  old_units_path = File.join(old_gen_path, UnitsDir) unless old_gen_path.empty?
+  new_units_path = File.join(new_gen_path, UnitsDir)
+
+  old_services = get_services(old_units_path)
+  new_services = get_services(new_units_path)
+
+  exit if old_services.empty? && new_services.empty?
+
+  all_services = get_active_targets_units(new_units_path)
+  maybe_changed = all_services & old_services
+  changed_services = get_changed_services(old_units_path, new_units_path, maybe_changed)
+  unchanged_oneshots = get_oneshot_services(maybe_changed - changed_services)
+
+  # These services should be running when this script is finished
+  services_to_run = all_services - unchanged_oneshots
+
+  # Only stop active services, otherwise we might get a 'service not loaded' error
+  # for inactive services that were removed in the current generation.
+  to_stop = get_active_units(old_services - new_services)
+  to_restart = changed_services
+  to_start = get_inactive_units(services_to_run - to_restart)
+
+  raise "daemon-reload failed" unless run_cmd('systemctl', '--user', 'daemon-reload')
+
+  # Exclude units that shouldn't be (re)started or stopped
+  no_manual_start, no_manual_stop, no_restart = get_restricted_units(to_stop + to_restart + to_start)
+  notify_skipped_units(to_restart & no_restart)
+  to_stop -= no_manual_stop
+  to_restart -= no_manual_stop + no_manual_start + no_restart
+  to_start -= no_manual_start
+
+  if to_stop.empty? && to_start.empty? && to_restart.empty?
+    print_service_msg("All services are already running", services_to_run)
+  else
+    puts "Setting up services" if @verbose
+    systemctl_action('stop', to_stop)
+    systemctl_action('start', to_start)
+    systemctl_action('restart', to_restart)
+    started_services = to_start + to_restart
+    if start_timeout_ms > 0 && !started_services.empty? && !@dry_run
+      failed = wait_and_get_failed_services(started_services, start_timeout_ms)
+      if failed.empty?
+        print_service_msg("All services are running", services_to_run)
+      else
+        puts
+        puts "Error. These services failed to start:", failed
+        show_failed_services_status(failed)
+        exit 1
+      end
+    end
+  end
+end
+
+def get_services(dir)
+  services = get_service_files(dir) if dir && Dir.exists?(dir)
+  Set.new(services)
+end
+
+def get_service_files(dir)
+  Dir.chdir(dir) { Dir['*[^@].{service,socket,timer}'] }
+end
+
+def get_changed_services(dir_a, dir_b, services)
+  services.select do |service|
+    a = File.join(dir_a, service)
+    b = File.join(dir_b, service)
+    (File.size(a) != File.size(b)) || (File.read(a) != File.read(b))
+  end
+end
+
+TargetDirRegexp = /^(.*\.target)\.wants$/
+
+# @return all units wanted by active targets
+def get_active_targets_units(units_dir)
+  return Set.new unless Dir.exists?(units_dir)
+  targets = Dir.entries(units_dir).map { |entry| entry[TargetDirRegexp, 1] }.compact
+  active_targets = get_active_units(targets)
+  active_units = active_targets.map do |target|
+    get_service_files(File.join(units_dir, "#{target}.wants"))
+  end.flatten
+  Set.new(active_units)
+end
+
+# @return true on success
+def run_cmd(*cmd)
+  print_cmd cmd
+  @dry_run || system(*cmd)
+end
+
+def systemctl_action(cmd, services)
+  return if services.empty?
+
+  verb = (cmd == 'stop') ? 'Stopping' : "#{cmd.capitalize}ing"
+  puts "#{verb}: #{services.join(' ')}"
+
+  cmd = ['systemctl', '--user', cmd, *services]
+  if @dry_run
+    puts cmd.join(' ')
+    return
+  end
+
+  output, status = Open3.capture2e(*cmd)
+  print output
+  # Show status for failed services
+  unless status.success?
+    # Due to a bug in systemd, the '--user' argument is not always provided
+    output.scan(/systemctl (?:--user )?(status .*?)['"]/).flatten.each do |status_cmd|
+      puts
+      run_cmd("systemctl --user #{status_cmd}")
+    end
+    exit 1
+  end
+end
+
+def systemctl(*cmd)
+  output, _ = Open3.capture2('systemctl', '--user', *cmd)
+  output
+end
+
+def print_cmd(cmd)
+  puts [*cmd].join(' ') if @verbose || @dry_run
+end
+
+def get_active_units(units)
+  filter_units(units) { |state| state == 'active' }
+end
+
+def get_inactive_units(units)
+  filter_units(units) { |state| state != 'active' }
+end
+
+def get_failed_units(units)
+  filter_units(units) { |state| state == 'failed' }
+end
+
+def filter_units(units)
+  return [] if units.empty?
+  states = systemctl('is-active', *units).split
+  units.select.with_index { |_, i| yield states[i] }
+end
+
+def get_oneshot_services(units)
+  return [] if units.empty?
+  types = systemctl('show', '-p', 'Type', *units).split
+  units.select.with_index do |_, i|
+    types[i] == 'Type=oneshot'
+  end
+end
+
+def get_restricted_units(units)
+  infos = systemctl('show', '-p', 'RefuseManualStart', '-p', 'RefuseManualStop', *units)
+          .split("\n\n")
+  no_manual_start = []
+  no_manual_stop = []
+  infos.zip(units).each do |info, unit|
+    no_start, no_stop = info.split("\n")
+    no_manual_start << unit if no_start.end_with?('yes')
+    no_manual_stop << unit if no_stop.end_with?('yes')
+  end
+  # Get units that should not be restarted even if a change has been detected.
+  no_restart_regexp = /^\s*X-RestartIfChanged\s*=\s*false\b/
+  no_restart = units.select { |unit| systemctl('cat', unit) =~ no_restart_regexp }
+  [no_manual_start, no_manual_stop, no_restart]
+end
+
+def wait_and_get_failed_services(services, start_timeout_ms)
+  puts "Waiting #{start_timeout_ms} ms for services to fail"
+  # Force the previous message to always be visible before sleeping
+  STDOUT.flush
+  sleep(start_timeout_ms / 1000.0)
+  get_failed_units(services)
+end
+
+def show_failed_services_status(services)
+  puts
+  services.each do |service|
+    run_cmd('systemctl', '--user', 'status', service)
+    puts
+  end
+end
+
+def print_service_msg(msg, services)
+  return if services.empty?
+  if @verbose
+    puts "#{msg}:", services.to_a
+  else
+    puts msg
+  end
+end
+
+def notify_skipped_units(no_restart)
+  puts "Not restarting: #{no_restart.join(' ')}" unless no_restart.empty?
+end
+
+setup_services(*ARGV)