What are alert rules in Alertmanager?

What are alert rules in Alertmanager?

Alert rules in Alertmanager define the conditions under which alerts are triggered. They help in monitoring and managing alerts effectively.

How do I create an alert rule?

To create an alert rule, you need to define a rule in YAML format, specifying the alert name, conditions, and labels.

Can you give me an example of an alert rule?

Sure! Here's a simple example:

- alert: HighCPUUsage
  expr: sum(rate(cpu_usage[5m])) by (instance) > 0.9
  for: 5m
  labels:
    severity: critical
  annotations:
    summary: "High CPU usage detected on {{ $labels.instance }}"

This rule triggers an alert if CPU usage exceeds 90% for 5 minutes.

What happens when an alert is triggered?

When an alert is triggered, Alertmanager sends notifications to the configured receivers, such as email, Slack, or PagerDuty.