add watchdog service

devices/gl-mt300n-v2/default.nix

@@ -146,10 +146,6 @@
           NET_RALINK_SOC="y";
           SWPHY = "y";
 
-          WATCHDOG = "y";
-          RALINK_WDT = "y";  # watchdog
-          MT7621_WDT = "y";  # or it might be this one
-
           GPIOLIB="y";
           GPIO_MT7621 = "y";
 
@@ -162,6 +158,9 @@
           PRINTK_TIME = "y";
         } // lib.optionalAttrs (config.system.service ? vlan) {
           SWCONFIG = "y";
+        } // lib.optionalAttrs (config.system.service ? watchdog) {
+          RALINK_WDT = "y";  # watchdog
+          MT7621_WDT = "y";  # or it might be this one
         };
       };
     };

examples/arhcive.nix

@@ -29,6 +29,7 @@ in rec {
     ../modules/network
     ../modules/vlan
     ../modules/ssh
+    ../modules/watchdog
   ];
 
   hostname = "arhcive";
@@ -67,43 +68,10 @@ in rec {
 
   services.sshd = svc.ssh.build { };
 
-  services.watchdog =
+  services.watchdog = svc.watchdog.build {
-    let
     watched = with config.services ; [ sshd dhcpc ];
-      spinupGrace = 60;
-      script = pkgs.writeAshScript "gaspode" {
-        runtimeInputs = [ pkgs.s6 ];
-      } ''
-      deadline=$(expr $(date +%s) + ${toString spinupGrace})
-      services=$@
-      echo started feeding the dog
-      exec 3> ''${WATCHDOG-/dev/watchdog}
-
-      healthy(){
-          test $(date +%s) -le $deadline && return 0
-
-          for i in $services; do
-              if test "$(s6-svstat -o up /run/service/$i)" != "true" ; then
-                 echo "service $i is down"
-                 return 1
-              fi
-          done
-      }
-
-      while healthy ;do
-          sleep 10
-          echo >&3
-      done
-      echo "stopped feeding the dog"
-      sleep 6000  # don't want s6-rc to restart
-    '';
-    in longrun {
-      name = "watchdog";
-      run =
-        "${script} ${lib.concatStringsSep " " (builtins.map (s: s.name) watched)}";
   };
 
-
   services.resolvconf = oneshot rec {
     dependencies = [ services.dhcpc ];
     name = "resolvconf";

modules/watchdog/default.nix

@@ -0,0 +1,24 @@
+{ lib, pkgs, config, ...}:
+let
+  inherit (lib) mkOption types;
+  inherit (pkgs) liminix;
+in
+{
+  options = {
+    system.service.watchdog =  mkOption {
+      type = liminix.lib.types.serviceDefn;
+    };
+  };
+  config.system.service.watchdog = liminix.callService ./watchdog.nix {
+    watched = mkOption {
+      description = "services to watch";
+      type = types.listOf liminix.lib.types.service;
+    };
+    headStart = mkOption {
+      description = "delay in seconds before watchdog starts checking service health";
+      default = 60;
+      type = types.int;
+    };
+  };
+  config.kernel.config.WATCHDOG = "y";
+}

modules/watchdog/gaspode.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+deadline=$(expr $(date +%s) + ${HEADSTART})
+services=$@
+echo started feeding the dog
+exec 3> ${WATCHDOG-/dev/watchdog}
+
+healthy(){
+    test $(date +%s) -le $deadline && return 0
+
+    for i in $services; do
+	if test "$(s6-svstat -o up /run/service/$i)" != "true" ; then
+	   echo "service $i is down"
+	   return 1
+	fi
+    done
+}
+
+while healthy ;do
+    sleep 10
+    echo >&3
+done
+echo "stopped feeding the dog"
+sleep 6000  # don't want s6-rc to restart

modules/watchdog/watchdog.nix

@@ -0,0 +1,12 @@
+{
+  liminix
+, lib
+}:
+{ watched, headStart } :
+let
+  inherit (liminix.services) longrun;
+in longrun {
+  name = "watchdog";
+  run =
+    "HEADSTART=${toString headStart} ${./gaspode.sh} ${lib.concatStringsSep " " (builtins.map (s: s.name) watched)}";
+}