92 lines
2.6 KiB
Nix
92 lines
2.6 KiB
Nix
# Defines a service for automatically collecting Nix garbage
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# periodically, without relying on the (ostensibly broken) Nix options
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# for min/max space available.
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{ config, lib, pkgs, ... }:
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let
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cfg = config.services.depot.automatic-gc;
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description = "Automatically collect Nix garbage";
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GiBtoKiB = n: n * 1024 * 1024;
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GiBtoBytes = n: n * 1024 * 1024 * 1024;
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gcScript = pkgs.writeShellScript "automatic-nix-gc" ''
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set -ueo pipefail
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readonly MIN_THRESHOLD_KIB="${toString (GiBtoKiB cfg.diskThreshold)}"
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readonly MAX_FREED_BYTES="${toString (GiBtoBytes cfg.maxFreed)}"
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readonly GEN_THRESHOLD="${cfg.preserveGenerations}"
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readonly AVAILABLE_KIB=$(df --sync /nix --output=avail | tail -n1)
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if [ "''${AVAILABLE_KIB}" -lt "''${MIN_THRESHOLD_KIB}" ]; then
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echo "Have ''${AVAILABLE_KIB} KiB, but want ''${MIN_THRESHOLD_KIB} KiB."
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echo "Triggering Nix garbage collection up to ''${MAX_FREED_BYTES} bytes."
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set -x
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${config.nix.package}/bin/nix-collect-garbage \
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--delete-older-than "''${GEN_THRESHOLD}" \
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--max-freed "''${MAX_FREED_BYTES}"
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else
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echo "Skipping GC, enough space available"
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fi
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'';
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in
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{
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options.services.depot.automatic-gc = {
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enable = lib.mkEnableOption description;
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interval = lib.mkOption {
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type = lib.types.str;
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example = "1h";
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description = ''
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Interval between garbage collection runs, specified in
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systemd.time(7) format.
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'';
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};
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diskThreshold = lib.mkOption {
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type = lib.types.int;
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example = "100";
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description = ''
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Minimum amount of space that needs to be available (in GiB) on
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the partition holding /nix. Garbage collection is triggered if
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it falls below this.
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'';
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};
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maxFreed = lib.mkOption {
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type = lib.types.int;
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example = "420";
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description = ''
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Maximum amount of space to free in a single GC run, in GiB.
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'';
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};
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preserveGenerations = lib.mkOption {
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type = lib.types.str;
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default = "90d";
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description = ''
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Preserve NixOS generations younger than the specified value,
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in the format expected by nix-collect-garbage(1).
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'';
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};
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};
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config = lib.mkIf cfg.enable {
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systemd.services.automatic-gc = {
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inherit description;
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script = "${gcScript}";
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serviceConfig.Type = "oneshot";
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};
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systemd.timers.automatic-gc = {
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inherit description;
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requisite = [ "nix-daemon.service" ];
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wantedBy = [ "multi-user.target" ];
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timerConfig = {
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OnActiveSec = "1";
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OnUnitActiveSec = cfg.interval;
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};
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};
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};
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}
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