I often run spot instances on EC2 (for Hadoop task jobs, temporary nodes, etc.) Some of these are long-running spot instances.
Its fairly easy to calculate the cost for on-demand or reserved EC2 instances - but how do I calculate the cost incurred for a specific node (or nodes) that are running as spot instances?
I am aware that the cost for a spot instance changes every hour depending on market rate - so is there any way to calculate the cumulative total cost for a running spot instance? Through an API or otherwise?