We have several hundred Linux VMs on EC2 and Google compute engine. We want to monitor basic things like disk free space and memory consumption, in the easiest and lightest way possible. Expectedly, VMs come and go pretty often, as load changes, etc.
Currently we use simple scripts that pull such information via SNMP. We don't need fancy app-specific monitoring since it is already being provided by app-specific means.
We tried Zenoss, and found it hard to use, and its documentation lacking.
We considered Nagios and its forks. We considered Sensu (but my boss is not a fan of RabbitMQ) and Ganglia, but all of them seem a bit too complicated for our very basic needs.
SaaS solutions like Circonus would be too expensive with the number of hosts we have.
Am I missing some obvious easy solution here? What would you recommend [against]?