From 9c37ce946826258711e15cd55ee221fa8fe02256 Mon Sep 17 00:00:00 2001
From: Gregor Kleen <gkleen@yggdrasil.li>
Date: Sat, 19 Feb 2022 15:51:23 +0100
Subject: zfssnap: ...

---
 hosts/surtr/zfs.nix        | 59 ++--------------------------------------------
 modules/zfssnap/zfssnap.py | 18 ++++++++++----
 2 files changed, 16 insertions(+), 61 deletions(-)

diff --git a/hosts/surtr/zfs.nix b/hosts/surtr/zfs.nix
index 3e42ef3e..3a69fd96 100644
--- a/hosts/surtr/zfs.nix
+++ b/hosts/surtr/zfs.nix
@@ -1,32 +1,5 @@
 { pkgs, config, ... }:
-let
-  snapshotNames = ["frequent" "hourly" "daily" "monthly" "yearly"];
-  snapshotCount = {
-    frequent = 24;
-    hourly = 24;
-    daily = 30;
-    monthly = 12;
-    yearly = 5;
-  };
-  snapshotTimerConfig = {
-    frequent = { OnCalendar = "*:0/5 UTC"; Persistent = true; };
-    hourly = { OnCalendar = "hourly UTC"; Persistent = true; };
-    daily = { OnCalendar = "daily UTC"; Persistent = true; };
-    monthly = { OnCalendar = "monthly UTC"; Persistent = true; };
-    yearly = { OnCalendar = "yearly UTC"; Persistent = true; };
-  };
-  snapshotDescr = {
-    frequent = "few minutes";
-    hourly = "hour";
-    daily = "day";
-    monthly = "month";
-    yearly = "year";
-  };
-
-  zfs = config.boot.zfs.package;
-
-  autosnapPackage = pkgs.zfstools.override { inherit zfs; };
-in {
+{
   config = {
     fileSystems = {
       "/nix" =
@@ -69,35 +42,7 @@ in {
         };
     };
 
-    systemd.services =
-      let mkSnapService = snapName: {
-            name = "zfs-snapshot-${snapName}";
-            value = {
-              description = "ZFS auto-snapshot every ${snapshotDescr.${snapName}}";
-              after = [ "zfs-import.target" ];
-              serviceConfig = {
-                Type = "oneshot";
-                ExecStart = "${autosnapPackage}/bin/zfs-auto-snapshot -k -p -u ${snapName} ${toString snapshotCount.${snapName}}";
-              };
-              restartIfChanged = false;
-
-              preStart = ''
-                ${zfs}/bin/zfs set com.sun:auto-snapshot=true surtr/safe
-              '';
-            };
-          };
-      in builtins.listToAttrs (map mkSnapService snapshotNames);
-
-    systemd.timers =
-      let mkSnapTimer = snapName: {
-            name = "zfs-snapshot-${snapName}";
-            value = {
-              wantedBy = [ "timers.target" ];
-              timerConfig = snapshotTimerConfig.${snapName};
-            };
-          };
-      in builtins.listToAttrs (map mkSnapTimer snapshotNames);
-
+    services.zfssnap.enable = true;
     services.zfs.trim.enable = false;
     services.zfs.autoScrub = {
       enable = true;
diff --git a/modules/zfssnap/zfssnap.py b/modules/zfssnap/zfssnap.py
index cb91564b..a05440a7 100644
--- a/modules/zfssnap/zfssnap.py
+++ b/modules/zfssnap/zfssnap.py
@@ -83,11 +83,21 @@ def prune(config, dry_run):
             keep.add(snap)
 
     within = config.gettimedelta('KEEP', 'within')
-    within_cutoff = _now() - within
+    if within > timedelta(seconds=0):
+        for base, snaps in items.items():
+            time_ref = max(snaps, key=lambda snap: snap['creation'], default=None)
+            if not time_ref:
+                logger.warn('Nothing to keep for ‘{base}’')
+                continue
 
-    for base, snap in [(base, snap) for base, snaps in items.items() for snap in snaps]:
-        if snap['creation'] >= within_cutoff:
-            keep_because(base, snap['name'], 'within')
+            logger.info('Using ‘{time_ref["name"]}’ as time reference for ‘{base}’')
+            within_cutoff = time_ref['creation'] - within
+
+            for snap in snaps:
+                if snap['creation'] >= within_cutoff:
+                    keep_because(base, snap['name'], 'within')
+    else:
+        logger.warn('Skipping rule ‘within’ since retention period is zero')
 
     prune_timezone = config.gettimezone('KEEP', 'timezone', fallback=tzlocal)
 
-- 
cgit v1.2.3