Managing EC2 Reservations with Ruby

Over the course of past couple of weeks the guys (and gals!) at Amazon have hosted a number of great 'AWS Start-Up' events to evangelize their services and share the stories of some of the startups that have come to fruition based on their platform. I've had a chance to attend the New York event, as well as present in Boston earlier today - kudos to the AWS team for putting together these events, we've met dozens of exciting new startups, entrepreneurs, and a lot of the AWS team itself.

Interestingly enough, watching the presentations and even talking to a lot of the developers in the crowd resulted in very similar pain points: server monitoring, management, and automation. Hence, below is a modest contribution (a Ruby script) for terminating an entire reservation of EC2 instances on the fly. Instead of manually specifying each instance id, you can give it a reservation number (r-xxxxxxx) and all the machines will be shut down:

> ec2-terminate-reservation.rb

#!/usr/bin/ruby
 
reservation = ARGV[0]
if reservation.nil?
    puts "No reservation id"
    exit
end
 
instances = []
collect = false
`ec2-describe-instances`.each_line { |l|
    l = l.chomp.split("\\t")
    if l[1] == reservation
        collect = true
        next
    end
 
    collect = false if collect and l.first == "RESERVATION"
 
    instances << l[1] if collect
}
 
puts "Terminating #{instances.size} servers: #{instances.join(' ')}"
`$EC2_HOME/bin/ec2-cmd TerminateInstances #{instances.join(' ')}`

ec2-terminate-reservation (Ruby script)

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To use this as any regular EC2 management command copy the provided file into your $EC2_HOME directory, and you're all ready to go. A sample use case would be: