Cabot is a self-hosted monitoring and alerting service that borrows the best ideas from tools such as PagerDuty, Pingdom and Nagios without their cost or complexity. You define checks against your servers and services, and Cabot alerts the right people when something fails.

Highlights

• Easy deployment, with Docker files included
• A web interface for configuring checks and on-call rotas
• Written in Python with Django

Maintenance note: the authors describe Cabot as stable and used in production by many teams, but it is not actively maintained and they are looking for new maintainers.