What tools and libraries for system monitoring have you used in your practice?

In practice, the following tools and libraries are often used for system monitoring:

• Prometheus — a monitoring and alerting system with a powerful query language PromQL. It allows collecting metrics from various services.
• Grafana — a data visualization tool, often used together with Prometheus to build dashboards.
• Zabbix — a comprehensive solution for monitoring servers, network equipment, and applications.
• ELK Stack (Elasticsearch, Logstash, Kibana) — for collecting, storing, and analyzing logs.
• Nagios — a classic tool for monitoring the status of services and servers.
• Telegraf — an agent for collecting metrics, often used with InfluxDB and Grafana.

Example: for monitoring a web server, you can configure Prometheus to collect metrics, and Grafana to display load and error graphs.