How are the alert rules in the Prometheus system configured and managed?

The alert rules in the Prometheus system can be configured and managed through either a configuration file or the Prometheus Web UI.

1. Setting Configuration:
   In the Prometheus configuration file, the alerting_rules field can be used to define alerting rules. For example:

alerting_rules:
  - alert: HighRequestRate
    expr: sum(rate(http_requests_total[5m])) > 100
    for: 5m
    labels:
      severity: critical
    annotations:
      summary: High request rate detected

In the example above, an alert rule named HighRequestRate is defined, which triggers an alert if the rate of total HTTP requests in the past 5 minutes exceeds 100 and continues for 5 minutes. The severity of the alert is set to critical and the summary is set to High request rate detected.

1. The Prometheus Web UI allows for the direct addition, editing, and deletion of alert rules within the Alerts interface. By selecting the “Alerts” page in the Prometheus UI and clicking the “New Alert” button, users can input expressions, tags, comments, and other information for the alert rule, then save it by clicking the “Save” button.

No matter how the alert rules are configured, once they are set up, Prometheus will regularly evaluate these rules and send notifications or carry out actions when triggering alert conditions. Users can check all current alert rules, their statuses, and history on Prometheus’ Alerts page.