Icinga
Icinga is an open-source computer system and network monitoring application. It was originally created as a fork of the Nagios system monitoring application in 2009.Icinga is attempting to get past perceived shortcomings in Nagios' development process, as well as adding new features such as a modern Web 2.0 style user interface, additional database connectors (for MySQL, Oracle, and PostgreSQL), and a REST API that lets administrators integrate numerous extensions without complicated modification of the Icinga core.
Nagios
Nagios Core , formerly known as Nagios, is a free and open-source computer-software application that monitors systems, networks and infrastructure. Nagios offers monitoring and alerting services for servers, switches, applications and services.