How does the Prometheus system gather metric data?

Prometheus system collects metric data in the following way:

1. Active pulling: Prometheus regularly sends HTTP requests to the target services being monitored to fetch metric data.
2. Server-side push: The monitored target service can push metric data to the Prometheus server, which offers several client libraries to make it easier for developers to implement server-side push.
3. Exporter: Prometheus offers various Exporter components to convert data from different monitoring systems into a format recognizable by Prometheus. For example, the Node Exporter is used to collect host-level metric data.
4. Middleware monitoring: Some middleware such as Kubernetes, Consul, etc., also offer plugins for integration with Prometheus, allowing for direct access to metric data.

Overall, the Prometheus system collects metric data through various methods, stores it in a time series database, and allows users to query and analyze this data.