Prometheus - An open-source systems monitoring and alerting toolkit.
runit - runit is a cross-platform Unix init scheme with service supervision, a replacement for sysvinit...
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
sysvinit - Savannah is a central point for development, distribution and maintenance of free software, both GNU and non-GNU.
StatsD - Simple daemon for easy stats aggregation.
Supervisor - Supervisor is a client/server system that allows its users to monitor and control a number of...