Assign EIPs given from the standard input to ENIs assigned to the instance

assign_EIPs.rb

#!/bin/env ruby
require 'rubygems'
require 'aws-sdk'

@ec2 = AWS::EC2.new({:region => ENV['AWS_DEFAULT_REGION']})
@eips_to_assign = ARGV # [EIP1 EIP2 EIP3 EIP4 ...]

DEBUG=false

def self.main
	instance = @ec2.instances[`curl http://169.254.169.254/latest/meta-data/instance-id`]

	puts "Instance #{instance.id} exists" if instance.exists? && DEBUG
	puts "Instance #{instance.id} is in a VPC " if instance.vpc? && DEBUG
	puts "Instance #{instance.id} has #{instance.network_interfaces.length} ENIs " if DEBUG

	#raise "# of EIPs needs to be factor of # of network interfaces" if @eips_to_assign.length % instance.network_interfaces.length
	naddr_assign_per_interface = (@eips_to_assign.length.to_f / instance.network_interfaces.length).ceil
	puts "# of EIPs to assign per ENI = #{naddr_assign_per_interface}" if DEBUG

	instance.network_interfaces.each do |interface|
		if interface.private_ip_addresses.length < naddr_assign_per_interface 
			@ec2.client.assign_private_ip_addresses({
				:network_interface_id => interface.id,
				:secondary_private_ip_address_count => naddr_assign_per_interface - interface.private_ip_addresses.length
				})
		end

		i = 0
		while i < naddr_assign_per_interface do
			eip = get_next_eip_to_assign
			if eip == nil
				break
			end
			if eip.associated?
				if eip.network_interface.id == interface.id
					puts "#{eip.public_ip} is already associated to #{interface.id}" if DEBUG
					i = i + 1
					next
				elsif has_network_interface?(instance, eip.network_interface)
					puts "#{eip.public_ip} is already associated to instace #{instance.id}" if DEBUG
					next
				else
					eip.disassociate
				end
			end
			success = associate_addr_to_instance(instance, interface, eip)
			if success
				i = i + 1
			else
				puts "ERROR: Failed to associate address #{eip.public_ip}" if DEBUG
			end
		end
	end
	puts output_private_ipaddresses instance
end

def self.get_next_eip_to_assign
	while @eips_to_assign.empty? == false
		ipaddr = @eips_to_assign.shift
		eip = @ec2.elastic_ips[ipaddr]
		if eip != nil
			return eip
		end
		puts "#{ipaddr} is not an valid EIP or not associated with the account. Will skip." if DEBUG
	end
	return nil
end

def self.has_network_interface? (instance, target_interface)
	instance.network_interfaces.each do |interface|
		return true if interface == target_interface
	end
	return false
end

def self.associate_addr_to_instance(instance, target_interface, eip)
	puts "associating #{eip.public_ip} to interface #{target_interface.id}" if DEBUG
	return true if self.associate_addr(target_interface, eip)

	instance.network_interfaces.each do |interface| 
		if target_interface.id != interface.id
			return true if self.associate_addr(interface, eip)
		end
	end
	return false
end

def self.associate_addr(interface, eip) 
	interface.private_ip_addresses.each do |private_ip|
		begin
			@ec2.client.associate_address({
				:private_ip_address => private_ip[:private_ip_address],
				:network_interface_id => interface.id,
				:allocation_id => eip.allocation_id,
				:allow_reassociation => true
			})
			puts "#{eip.public_ip} is associated to #{interface.id}" if DEBUG
			return true
		rescue
			puts $! if DEBUG
		end
	end
	return false
end	

def self.output_private_ipaddresses(instance)
	ipaddrs = []
	instance.network_interfaces.each do |interface|
		interface.private_ip_addresses.each do |private_ip|
			ipaddrs.push private_ip[:private_ip_address]
		end
	end
	ipaddrs.join(',')
end	

main