I am monitoring a gauge metrics with Prometheus, and I want to fire a alert message to Slack channel every time this metrics value changes, also alert message should contains the current value of metrics.
I tried this, here is my rules.yml:
- alert: Test
expr: delta(My_Metrics[5m]) != 0
for: 30s
labels:
severity: page
annotations:
summary: '{{$value}}'
For pass on the metrics value from rules.yml to AlertManager, I put {{$value}} in summary, thought it is the value of metrics, but then I figure out it is the result of expr. How can I put metrics value in summary section? or is there any other way to achieve what I expected?