I am looking for a way to collect data remotely from various cloud instances (EC2, Rackpsace). The Rackspace API provides no way for collecting server performance metrics (ie load average, cpu usage, memory) via it's API, otherwise this would have never been asked.
I started looking at solutions like Capistrano or Mcollective (I have also considered collectd), but I am unsure of which one would best suit my application. I am trying to avoid using ssh keys for trending purposes (I don't want to have to keep logging in to collect these metrics) The script I am writing is a Ruby script which reboots a cloud server if it's load average is over a certain number. Because these providers don't expose these metrics via their API, I am looking at a way to gather them myself, and I am new to the Ruby community so after briefing over the documentation for all of these tools, I still haven't been able to get a sense of which framework would work best, or if there are other alternatives.
It sounds like Capistrano is more suited to be a deployment tool, although it can perform remote tasks, so after I read the documentation for that it was pretty much out for the purposes of my script.
MCollective looks really attractive for what I am trying to do but it seems I would have to write my own RPC style plugin for this purpose.
I've also considered plugging into some greater monitoring system such as Nagios, Munin, Zenoss, Hyperic, etc, but I'd rather not install some large bulk monitoring system when all I want to collect is but a few simple metrics.
If your intention is to trigger certain actions based on the system performance (like restarting when cpu usage is too high), you should check out god.
I'm not sure if this is also useful when you want to generate some performance statistics over a longer time period. Personally, I'm using Munin for this, but if you don't like it maybe you can find something on Ruby Toolbox | Server Monitoring.