Python program to reboot multiple ec2 instances together. This can be used for performing some scheduled restart of EC2 machines in an Amazon account. I used python boto library for performing this operation.

EC2Reboot.py

__author__ = 'Amal G Jose'

import boto.ec2

class EC2Reboot(object):

    def __init__(self):
        self.instance_id_list = ["i-xxxxxx", "i-xxxxxx", "i-xxxxx", "i-xxxx", "i-xxxxx", "i-xxxxx", "i-xxxxx"]
        self.aws_access_key = "XXXXXXXXXXX"
        self.aws_secret_key = "XXXXXXXXXXX"
        self.region = "xx-xxxx-x"
        self.conn = boto.ec2.connect_to_region(self.region,
                    aws_access_key_id=self.aws_access_key,
                    aws_secret_access_key=self.aws_secret_key)

    def restart_instances(self):
        try:
            print "Rebooting instances: %s" %(str(self.instance_id_list))
            self.conn.reboot_instances(self.instance_id_list)
        except Exception, e:
            print "Error occurred while restarting instances: %s" %(str(e))

if __name__ == '__main__':
    restart = EC2Reboot()
    restart.restart_instances()

I was trying to get a similar thing done but realized that AWS throttle the API access so If you reboot multiple instances at once this will create a bit of problem. You might want to put a sleep for like 5 seconds between each attempt.