PromQL itself does not support templating. You do have a few choices of doing this, though:

• Have whatever deployment tool you're using (Ansible, Chef, Puppet) populate that $1 with a regular expression that lists all the assets you're interested in (and use the =~ matcher instead of = in your PromQL expression).

• Create another metric (either by pushing it to a Pushgateway or by defining it in a separate rule file) with an asset_id label populated with all the asset IDs you're interested in, e.g.:

  should_alert{asset_id="123"} 1
  should_alert{asset_id="124"} 1
  should_alert{asset_id="125"} 1
  

  and then define your alert expression as:

  expr: test_value >= 4 and on (asset_id) should_alert