collectd
A daemon that collects system performance statistics periodically, and provides tons of plugins to store and analyze these values
linux windows osx open-source monitoring c
ConfigCat
ConfigCat is a feature flags as a service. It gives you a web based dashboard to manage your feature flags + SDKs to integrate those feature flags into your applications. ConfigCat enables you to use the same feature flags in your mobile apps, websites and server-side applications. It offers all features for free. You get an enterprise-ready SLA with the pricing plans.
linux osx windows open-source free commercial ci cd config-management go java net nodejs php python ruby
Monit
An open source utility for managing and monitoring processes, programs, files, directories and filesystems
linux osx open-source monitoring process-mgmt c
Rex
A agent-less server orchestration tool built on Perl
linux windows osx open-source orchestration perl
Zabbix
An open source, enterprise-class monitoring framework
linux windows osx open-source monitoring c