OpenCensus - Application and Data, Monitoring, and Monitoring Tools
Zabbix - Track, record, alert and visualize performance and availability of IT resources
InsightCat - Full-stack monitoring platform for your software and hardware. InsightCat is a cloud-based and AI-powered solution to enhance your system health estate through infrastructure monitoring and alerting capabilities.
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.
Thanos.io - Open source, highly available Prometheus setup with long term storage capabilities.
Prometheus - An open-source systems monitoring and alerting toolkit.