Prometheus is a very powerful open-source monitoring and alerting system suitable for dynamic environments like in Cloud space. That collects metrics from monitored targets by scraping metrics HTTP endpoints on these targets.

Prometheus is capable of recording any purely numeric time series, for both machine-centric monitorings like Linux systems as well as monitoring of highly dynamic service-oriented architectures.

Prometheus server-This scrapes and stores time series data from client systems and applications. 

Prometheus server has been tested by Apps4Rent engineers and it works well on Debian 11:

Features of Prometheus on Debian 11: 

• A multi-dimensional data model with time series data identified by metric name and key/value pairs
• Single server nodes are autonomous and don't rely on distributed storage.
• Prometheus time series collection uses pull model over HTTP protocol.
• pushing time series is supported via an intermediary gateway.
• Prometheus has support for multiple modes of graphing and dashboarding.
• Support for hierarchical and horizontal federation.
• An HTTP pull model for time series collection.

Disclaimer:  Apps4Rent does not offer commercial licenses of any of the products mentioned above. The products come with open source licenses.

Default ports: 

• SSH:22
• HTTP: 80
• HTTPS:443