Prometheus Alertmanager Expression Problem/Question(s) concerning Lists - expression

Question

I am trying to create an prometheus-alert-expression that checks if a mountpoint is mounted and sends an alert if the mountpoint is missing .. The Idea was something like this:
groups:
- name: mountpoints
rules:
- alert: /ghome missing
expr: absent(node_filesystem_avail_bytes{mountpoint="/ghome", instance="my.machine.org:9100"})
for: 60s
labels:
severity: critical
annotations:
summary: "/ghome missing on ({{ $labels.instance }})."
description: "VALUE = {{ $value }}\n LABELS = {{ $labels }}"
This kinda works. But is there a way of passing a list/vector to the mountpoint(s) and/or instance(s).
Using this Expression I'll have to write an alert-rule for each instance and each mountpoint.
I had the Idea of trying regular-Expressions like
expr: absent(node_filesystem_avail_bytes{mountpoint=~"/ghome|/something|/other", instance=~"my.machine.org:9100|another.machine.org:9100"})
.. but this obviously does not work.
Does anybody have an idea how to implement this ?
Greetings
Volker

Answer 1

When we pass an expression such as absent(my_metric{label=~"1|2"}), this is evaluated as such:
my_metric{label=~"1|2"} might return 4 possible results:
No result
my_metric{label="1"}
my_metric{label="2"}
both my_metric{label="1"} and my_metric{label="2"}
And the absent function is then called upon these results, and for absent to return "1" it will only do so when there are no results. Missing the case when 1 of them is absent.
Unfortunately there's no one-liner for this, we'll have to be explict with absent, we can either have multiple alert-rules or use the or operator such as:
absent(my_metric{label="1"}) or absnet(my_metrci{label="2"})