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
NewRelic - New Relic is a Software Analytics company that makes sense of billions of metrics across millions of apps. We help the people who build modern software understand the stories their data is trying to tell them.
LiteSpeed Web Server - LiteSpeed Web Server (LSWS) is a high-performance Apache drop-in replacement.