collectd

A daemon that collects system performance statistics periodically, and provides tons of plugins to store and analyze these values

     

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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.

     

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Monit

An open source utility for managing and monitoring processes, programs, files, directories and filesystems

     

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Rex

A agent-less server orchestration tool built on Perl

     

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Zabbix

An open source, enterprise-class monitoring framework

     

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