nixos-config/modules/services/monitoring.nix

{ config, ... }:
{
  services = {
    prometheus = {
      enable = true;
      port = 9001;
      exporters = {
        node = {
          enable = true;
          enabledCollectors = [ "systemd" ];
          port = 9002;
        };
      };
      scrapeConfigs = [
        {
          job_name = "${config.networking.hostName}";
          static_configs = [
            {
              targets = [ "127.0.0.1:${toString config.services.prometheus.exporters.node.port}" ];
            }
          ];
        }
      ];
    };
  };
  networking.firewall = {
    allowedTCPPorts = [
      9001
      22
      9123 # always also allow ssh :screaming:
    ];
  };
}