molder

https://github.com/kigster/molder

Molder is a handy command line tool for generating and running (in parallel, using a pool of processes with a configurable size) a set of related and yet different commands. A YAML file defines both the attributes and the command template, and Molder then merges the two with CLI arguments to give you a consistent set of commands for, eg. provisioning thousands of virtual hosts in a cloud. The gem is not limnited to any particular cloud, tool, or a command, and can be used across various domains to generate a consistent set of commands based on the YAML-supplied attributes and templates, that might vary across custom dimensions. For example, you could generate 600 provisioning commands for hosts in EC2, numbered from 1 to 100, but constrained to the zones "a", "b", "c", and data centers "dc" (values: ['us-west2', 'us-east1' ]). Behind the scenes Molder uses another Ruby gem Parallel — for actually running the provisioning commands.