Using Amazon’s Web Services from Ruby – Jonathan Younger

Right Scale has a great gem:
gem install right_aws
RightScale RightAws::Sqs
RightScale RightAws::Ec2

They will automatically retry errors for you.

gem install kato
Kato – EC2 Pool Manager

require 'rubygems'
requrie 'right_aws'
RightAws::RightAWSParser.xml_lib = 'libxml'

SQS = RightAws::Sqs.new(access_id, access_key) #get an SQS object
queue = SQS.queue("name_of_queue") #create a or get a reference to an existing queue
queue.psuh "put message in the queue" #8k max
queue.size # get an approximate number of message in the queue
message = queue.receive #
message.delete # if you don't delete your messages they will show up again
</pre>


require 'rubygems'
requrie 'right_aws'
RightAws::RightAWSParser.xml_lib = 'libxml'
EC2 = RightAsw::Ec2.new(access_id, access_key)
EC2.describe_instances # get a hash of running instances
EC2.run_instances("name_of_ami", minium_instances_to, max) # start up instances
EC2.terminate_instances(["id1", "id2"]) # turn them off
</pre>


require 'kato'
# Let Kato manage your instances
pool = Kato::PoolSupervisor.new(config)
pool.run
</pre>

Kato can manage multiple pools.  You can give it a min and max number of instances and give it an uptime interval.  Amazon charges by the hour for the machine so you if you start it up you may as well leave it on for the full hour.