Alertmanager configuration and routing

It is a common misconception amongst users first starting out with Prometheus that Prometheus itself is responsible for getting alerts to their destination, whether that be Slack, PagerDuty, OpsGenie, or another platform. Alertmanager is the oft-forgotten yet critical component that handles getting the alerts coming from Prometheus to their destination. The divide between the two can be confusing at first, but if you’re familiar with Prometheus already, then you know that Prometheus evaluates alerting rules in a constant loop and sends them to one or more Alertmanager instances once they meet a specified for duration in the alert. From there, Alertmanager determines where the alert information should be sent. Let’s look at how Alertmanager accomplishes that.

Routing

Routing is the core of what the Alertmanager does; it processes an alert by walking a tree structure of routes to determine what receiver(s) an alert should be...