From e6e4665a180b38ef4225d85b63fb8ed1101a77cc Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Sun, 9 Jun 2024 22:37:45 +0100
Subject: [PATCH] flip dependencies for triggered/controlled services

Instead of treating the trigger as the "main" service and the
triggered service as subsidary, now we treat the triggered
service as the service and the trigger as "subsidary". This
needs some special handling when we work out which services
go in the default bundle, but it works better for declaring
dependencies on triggered services because it means the
dependency runs after the triggered service comes up, not
just when the watcher-for-events starts
---
 modules/mount/service.nix               | 26 +++++++++++++------------
 modules/s6/default.nix                  |  5 ++++-
 modules/service-trigger/default.nix     |  6 +++---
 modules/service-trigger/rule.nix        |  7 +++----
 pkgs/liminix-tools/services/builder.sh  |  2 +-
 pkgs/liminix-tools/services/default.nix |  5 ++++-
 6 files changed, 29 insertions(+), 22 deletions(-)

diff --git a/modules/mount/service.nix b/modules/mount/service.nix
index ab0b91bd..54cd2c2a 100644
--- a/modules/mount/service.nix
+++ b/modules/mount/service.nix
@@ -7,19 +7,21 @@
 let
   inherit (liminix.services) longrun oneshot;
   device = "/dev/disk/by-partlabel/${partlabel}";
+  name = "mount.${lib.strings.sanitizeDerivationName (lib.escapeURL mountpoint)}";
   options_string =
     if options == [] then "" else "-o ${lib.concatStringsSep "," options}";
-  mount_service = oneshot {
-    name = "mount.${lib.escapeURL mountpoint}";
-    timeout-up = 3600;
-    up = "mount -t ${fstype} ${options_string} ${device} ${mountpoint}";
-    down = "umount ${mountpoint}";
-  };
-in svc.uevent-rule.build {
-  service = mount_service;
-  symlink = device;
-  terms = {
-    partname = partlabel;
-    devtype = "partition";
+  controller = svc.uevent-rule.build {
+    serviceName = name;
+    symlink = device;
+    terms = {
+      partname = partlabel;
+      devtype = "partition";
+    };
   };
+in oneshot {
+  inherit name;
+  timeout-up = 3600;
+  up = "mount -t ${fstype} ${options_string} ${device} ${mountpoint}";
+  down = "umount ${mountpoint}";
+  inherit controller;
 }
diff --git a/modules/s6/default.nix b/modules/s6/default.nix
index cd05de76..256ee73c 100644
--- a/modules/s6/default.nix
+++ b/modules/s6/default.nix
@@ -13,7 +13,10 @@ let
     let
       defaultDefaultTarget = bundle {
         name = "default";
-        contents = builtins.attrValues config.services;
+        contents =
+          builtins.map
+            (s: if (s ? controller && s.controller != null) then s.controller else s)
+            (builtins.attrValues config.services));
       };
       servicesAttrs = {
         default = defaultDefaultTarget;
diff --git a/modules/service-trigger/default.nix b/modules/service-trigger/default.nix
index eb3f7bd5..3bed214b 100644
--- a/modules/service-trigger/default.nix
+++ b/modules/service-trigger/default.nix
@@ -15,9 +15,9 @@ in {
   };
   config = {
     system.service.uevent-rule = liminix.callService ./rule.nix {
-      service = mkOption {
-        description = "the service to run when the rule matches";
-        type = liminix.lib.types.service;
+      serviceName = mkOption {
+        description = "name of the service to run when the rule matches";
+        type = types.str;
       };
       terms = mkOption {
         type = types.attrs;
diff --git a/modules/service-trigger/rule.nix b/modules/service-trigger/rule.nix
index a0d7578e..a851e529 100644
--- a/modules/service-trigger/rule.nix
+++ b/modules/service-trigger/rule.nix
@@ -4,7 +4,7 @@
 , serviceFns
 , lib }:
 {
-  service, terms, symlink
+  serviceName, terms, symlink
 }:
 let
   inherit (liminix.services) longrun;
@@ -18,8 +18,7 @@ let
           attrs));
   termsString = stringify terms;
 in longrun {
-  name = "watch-for-${service.name}";
+  name = "watch-for-${serviceName}";
   isTrigger = true;
-  buildInputs = [ service ];
-  run = "${uevent-watch}/bin/uevent-watch ${if symlink != null then "-n ${symlink}" else ""} -s ${service.name} ${termsString}";
+  run = "${uevent-watch}/bin/uevent-watch ${if symlink != null then "-n ${symlink}" else ""} -s ${serviceName} ${termsString}";
 }
diff --git a/pkgs/liminix-tools/services/builder.sh b/pkgs/liminix-tools/services/builder.sh
index e163fe07..5f1ecb68 100644
--- a/pkgs/liminix-tools/services/builder.sh
+++ b/pkgs/liminix-tools/services/builder.sh
@@ -11,7 +11,7 @@ test -n "$contents" && for d in $contents; do
     touch $out/${name}/contents.d/$d
 done
 
-for i in timeout-up timeout-down run notification-fd up down finish consumer-for producer-for pipeline-name restart-on-upgrade; do
+for i in controllerName timeout-up timeout-down run notification-fd up down finish consumer-for producer-for pipeline-name restart-on-upgrade; do
     test -n "$(printenv $i)" && (echo "$(printenv $i)" > $out/${name}/$i)
 done
 
diff --git a/pkgs/liminix-tools/services/default.nix b/pkgs/liminix-tools/services/default.nix
index 9a09963e..2a466030 100644
--- a/pkgs/liminix-tools/services/default.nix
+++ b/pkgs/liminix-tools/services/default.nix
@@ -39,6 +39,7 @@ let
     , contents ? []
     , buildInputs ? []
     , isTrigger ? false
+    , controller ? null
   } @ args:
     stdenvNoCC.mkDerivation {
       # we use stdenvNoCC to avoid generating derivations with names
@@ -46,9 +47,11 @@ let
       inherit name serviceType up down run finish notification-fd
         producer-for consumer-for pipeline-name timeout-up timeout-down;
       restart-on-upgrade = isTrigger;
-      buildInputs = buildInputs ++ dependencies ++ contents;
+      buildInputs = buildInputs ++ dependencies ++ contents ++ lib.optional (controller != null) controller;
       dependencies = map (d: d.name) dependencies;
       contents = map (d: d.name) contents;
+      inherit controller;
+      controllerName = if controller ? name then controller.name else null;
       builder = ./builder.sh;
     };