Prometheus is a free software application used for event monitoring and alerting.
https://prometheus.io

Available solutions:

Name	Kind	Description	Pricing
Nagios to Prometheus See more	Reactor	Push Nagios plugin perfdata to Prometheus PushGateway	FREE
Prometheus Pusher See more	Reactor	Push metrics to Prometheus PushGateway	FREE
Query See more	Unit	Query data from the Prometheus HTTP API	FREE

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