Find EC2 worker instances

find_workers.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'fileutils'
require 'right_aws'
require 'optparse'
require 'pp'



options = {}
optparse = OptionParser.new do|opts|
   opts.banner = "Usage: bootstrap.rb [options]"
 
   # Define the options, and what they do
   options[:"access-key"] = nil
   opts.on( '-a', '--access-key ACCESS_KEY', 'AWS Access Key' ) do |x|
     options[:"access-key"] = x
   end

   options[:"secret-key"] = nil
   opts.on( '-s', '--secret-key SECRET_KEY', 'AWS Secret Key' ) do |x|
     options[:"secret-key"] = x
   end

   options[:"stack-name"] = nil
   opts.on( '-n', '--stack-name STACK_NAME', 'CloudFormation Stack Name' ) do |x|
     options[:"stack-name"] = x
   end
end

optparse.parse!

puts("parsed args")


logger = Logger::new(STDOUT)
logger.level = Logger::ERROR


instance_id = `curl -s http://169.254.169.254/latest/meta-data/instance-id`.chomp
puts("instance_id = #{instance_id}")


ec2 = RightAws::Ec2.new(options[:'access-key'], options[:'secret-key'], :logger => logger)
puts("signed into ec2")

workers = []
puts(" finding workers:")
instances = ec2.describe_instances
for instance in instances
  if instance.has_key? :tags \
    and instance[:tags].has_key? "aws:autoscaling:groupName" \
    and instance[:tags].has_key? "aws:cloudformation:stack-name" \
    and instance[:tags]["aws:cloudformation:stack-name"] == \
    options[:'stack-name'] and instance[:aws_state] == "running"
      puts("got a stack member")
      workers.push instance
  end
end
puts("found #{workers.size} workers")


numcores = 4

master_ipaddr = `curl -s http://169.254.169.254/latest/meta-data/local-ipv4`.chomp
puts "#{master_ipaddr} #{numcores}"
  
workers.each_with_index do |worker, i|
  puts "#{worker[:private_ip_address]} #{numcores}"
end

Credit due to Dan Tenenbaum for the original, which can be found here:

https://hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/BiocCloud/inst/CloudFormation/bootstrap_plain.rb