We have implemented a monitoring solution in node.js, which does some basic checks for database integrity and API up-time. We want to expand this system to collect basic system stats of our Linux servers like CPU and disc usage. Some of these servers are behind a firewall which is out of our control, with only some very basic ports open (ssh,ftp,http,https).
How can I gather the system information of these servers in node.js. Are there monitoring systems which expose these information through a (secured) RESTful API?