Serilog - Backend Development and Utilities
Zabbix - Track, record, alert and visualize performance and availability of IT resources
log4net - log4net is a tool to help the programmer output log statements to a variety of output targets.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
LOGBack - Logging framework
Prometheus - An open-source systems monitoring and alerting toolkit.