README

[nix-profile-gc] / modules / profile-gc.nix

diff --git a/modules/profile-gc.nix b/modules/profile-gc.nix
index 02b723829fba668014722f18faa633a647781d70..5444798568249e38724cb965ea3068d0747d2afd 100644 (file)
--- a/modules/profile-gc.nix
+++ b/modules/profile-gc.nix
@@ -1,3 +1,18 @@
+# nix-profile-gc: More gently remove old profiles
+# Copyright (C) 2022 Scott Worley <scottworley@scottworley.com>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3.
+#
+# This program 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
 { lib, config, pkgs, ... }:
 let
   inherit (lib) escapeShellArg;
@@ -14,7 +29,7 @@ in {
       dryRun = lib.mkOption {
         description = "Say what would have been deleted rather than actually deleting profiles";
         type = lib.types.bool;
-        default = true;
+        default = false;
       };
       keepLast = lib.mkOption {
         description = ''
@@ -49,16 +64,23 @@ in {
           awhile (so keepLatest won't protect them) generates a bunch of broken profiles (so
           keepLast won't protect them) while trying to get up to date.
 
-          This is approximate and has a useful granularity of an hour
-          (config.systemd.timers.profile-gc-log-active.timerConfig.OnUnitActiveSec).
-          Do not set less than this.
+          This threshold is approximate, see activeMeasurementGranularity.
+          Do not set less than activeMeasurementGranularity!
         '';
-        # We admonish the user "Do not set less than this." and check it at runtime rather
-        # than verifying this with an assertion now because parsing these durations at
-        # configuration-time requires import-from-derivation, which we want to avoid.  :(
+        # We admonish the user "Do not set less than activeMeasurementGranularity!" and check
+        # it at runtime rather than verifying this with an assertion at evaluation time because
+        # parsing these durations at evaluation-time requires import-from-derivation, which we
+        # want to avoid.  :(
         type = lib.types.str;
         default = "5 days";
       };
+      activeMeasurementGranularity = lib.mkOption {
+        description = ''
+          How often to make a note of the currently-active profiles.  This is the useful
+          granularity and minimum value of activeThreshold.
+        '';
+        default = "1 hour";
+      };
       keepLatest = lib.mkOption {
         description = ''
           Keep all profiles younger than this duration (systemd.time format).
@@ -98,7 +120,7 @@ in {
       fi
 
       alive_threshold="$(< ${parse-duration cfg.activeThreshold})"
-      alive_loginterval="$(< ${parse-duration config.systemd.timers.profile-gc-log-active.timerConfig.OnUnitActiveSec})"
+      alive_loginterval="$(< ${parse-duration cfg.activeMeasurementGranularity})"
       if (( alive_threshold < alive_loginterval ));then
         echo "Liveness threshold is too low.  Not doing any profile garbage collection." >&2
         exit 0
@@ -190,7 +212,8 @@ in {
     '';
     systemd.timers.profile-gc-log-active = {
       wantedBy = [ "timers.target" ];
-      timerConfig.OnUnitActiveSec = "1 hour";
+      timerConfig.OnActiveSec = cfg.activeMeasurementGranularity;
+      timerConfig.OnUnitActiveSec = cfg.activeMeasurementGranularity;
     };
     systemd.services.profile-gc-log-active = {
       description =