Zabbix - Track, record, alert and visualize performance and availability of IT resources
Apache HTTP Server - Apache httpd has been the most popular web server on the Internet since April 1996
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.
Apache Tomcat - An open source software implementation of the Java Servlet and JavaServer Pages technologies
Prometheus - An open-source systems monitoring and alerting toolkit.
LiteSpeed Web Server - LiteSpeed Web Server (LSWS) is a high-performance Apache drop-in replacement.