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

Nagios Core

Nagios Core network monitoring software is a powerful, enterprise-class host, server, application, monitoring and alerting tool

     

linux solaris bsd open-source monitoring c

testssl.sh

A command-line tool which checks a server's service on any port for the support of TLS/SSL ciphers, protocols as well as some cryptographic flaws. It's designed to provide clear output for your "is this good or bad" decision.

     

linux osx open-source security shell

Zabbix

An open source, enterprise-class monitoring framework

     

linux windows osx open-source monitoring c