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.
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Monit
An open source utility for managing and monitoring processes, programs, files, directories and filesystems
linux osx open-source monitoring process-mgmt c
Pallet
A tool to provision and maintain servers across various cloud platforms as well as virtual machine platforms, without any dependencies. Provides cloud and operating system independence.
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Statman
Statman makes it possible to instrument and collect statistics from your high-traffic production Erlang systems with very low overhead. The collected data points are aggregated in the VM and can be sent to services like Graphite, Munin, New Relic, etc.
linux windows osx open-source monitoring erlang
Zabbix
An open source, enterprise-class monitoring framework
linux windows osx open-source monitoring c