gistfile1.txt

{ pkgs , ... }:
{
  systemd.services.run-vm = {
    enable = true;
    wants = [ "healthcheck-vm.timer" ];
    before = [ "healthcheck-vm.timer" ];

    script = ''
      while true; do
        echo "I'm up! :)"
        sleep 10
      done
    '';
  };

  systemd.timers.healthcheck-vm = {
    enable = true;
    description = "Verify the VM is listening";
    partOf = [ "run-vm.service"];

    timerConfig = {
      OnActiveSec = 900;
      OnCalendar = "hourly";
      Unit = "healthcheck-vm.service";
      Persistent = "yes";
    };
  };

  systemd.services.healthcheck-vm = {
    enable = true;

    script = ''
      if [[ $(($RANDOM % 2)) -eq 0 ]]; then
        echo "up!"
      else
        systemctl restart run-vm.service
      fi
    '';
  };
}