From 5457fdf27380a821b2944f1ab1ccee1e20a07675 Mon Sep 17 00:00:00 2001
From: Robert Kovacsics <robert.kovacsics@cambridgeconsultants.com>
Date: Thu, 29 Sep 2022 11:44:04 +0100
Subject: [PATCH 1/2] gitlab-runner: Install `clear-docker-cache` script

---
 .../continuous-integration/gitlab-runner/default.nix     | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/tools/continuous-integration/gitlab-runner/default.nix b/pkgs/development/tools/continuous-integration/gitlab-runner/default.nix
index 0c2d18393390..d55ea9ae52ab 100644
--- a/pkgs/development/tools/continuous-integration/gitlab-runner/default.nix
+++ b/pkgs/development/tools/continuous-integration/gitlab-runner/default.nix
@@ -1,4 +1,4 @@
-{ lib, buildGoModule, fetchFromGitLab, fetchurl }:
+{ lib, buildGoModule, fetchFromGitLab, fetchurl, bash }:
 
 let
   version = "15.4.0";
@@ -14,6 +14,9 @@ buildGoModule rec {
     "-X ${commonPackagePath}.REVISION=v${version}"
   ];
 
+  # For patchShebangs
+  buildInputs = [ bash ];
+
   vendorSha256 = "sha256-S0x1b2ITtqMoqdssoTgnolDC6Tyq3IdkJqxwZ29qCyU=";
 
   src = fetchFromGitLab {
@@ -45,6 +48,10 @@ buildGoModule rec {
     rm helpers/docker/auth/auth_test.go
   '';
 
+  postInstall = ''
+    install packaging/root/usr/share/gitlab-runner/clear-docker-cache $out/bin
+  '';
+
   preCheck = ''
     # Make the tests pass outside of GitLab CI
     export CI=0

From c8eae7a5261a0d2ceaf0ad8a8b08050ec5bf40f2 Mon Sep 17 00:00:00 2001
From: Robert Kovacsics <robert.kovacsics@cambridgeconsultants.com>
Date: Thu, 29 Sep 2022 11:44:40 +0100
Subject: [PATCH 2/2] nixos/gitlab-runner: Add
 `gitlab-runner.clear-docker-cache` service

---
 .../continuous-integration/gitlab-runner.nix  | 53 +++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/nixos/modules/services/continuous-integration/gitlab-runner.nix b/nixos/modules/services/continuous-integration/gitlab-runner.nix
index fb148e7cffb5..2050e04d55cd 100644
--- a/nixos/modules/services/continuous-integration/gitlab-runner.nix
+++ b/nixos/modules/services/continuous-integration/gitlab-runner.nix
@@ -453,6 +453,43 @@ in
         };
       });
     };
+    clear-docker-cache = {
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = lib.mdDoc ''
+          Whether to periodically prune gitlab runner's Docker resources. If
+          enabled, a systemd timer will run {command}`clear-docker-cache` as
+          specified by the `dates` option.
+        '';
+      };
+
+      flags = mkOption {
+        type = types.listOf types.str;
+        default = [ ];
+        example = [ "prune" ];
+        description = lib.mdDoc ''
+          Any additional flags passed to {command}`clear-docker-cache`.
+        '';
+      };
+
+      dates = mkOption {
+        default = "weekly";
+        type = types.str;
+        description = lib.mdDoc ''
+          Specification (in the format described by
+          {manpage}`systemd.time(7)`) of the time at
+          which the prune will occur.
+        '';
+      };
+
+      package = mkOption {
+        default = config.virtualisation.docker.package;
+        defaultText = literalExpression "config.virtualisation.docker.package";
+        example = literalExpression "pkgs.docker";
+        description = lib.mdDoc "Docker package to use for clearing up docker cache.";
+      };
+    };
   };
   config = mkIf cfg.enable {
     warnings = (mapAttrsToList
@@ -497,6 +534,22 @@ in
         KillMode = "process";
       };
     };
+    # Enable periodic clear-docker-cache script
+    systemd.services.gitlab-runner-clear-docker-cache = {
+      description = "Prune gitlab-runner docker resources";
+      restartIfChanged = false;
+      unitConfig.X-StopOnRemoval = false;
+
+      serviceConfig.Type = "oneshot";
+
+      path = [ cfg.clear-docker-cache.package pkgs.gawk ];
+
+      script = ''
+        ${pkgs.gitlab-runner}/bin/clear-docker-cache ${toString cfg.clear-docker-cache.flags}
+      '';
+
+      startAt = optional cfg.clear-docker-cache.enable cfg.clear-docker-cache.dates;
+    };
     # Enable docker if `docker` executor is used in any service
     virtualisation.docker.enable = mkIf (
       any (s: s.executor == "docker") (attrValues cfg.services)