gistfile1.py

#!/usr/bin/env python
import os
import urllib
import boto
from boto import ec2

def get_seeds(conn, cluster):
    all_instances = conn.get_all_instances(filters={"tag:type": "*", "tag:cluster": cluster})
    seeds = []
    for reservation in all_instances:
        for instance in reservation.instances:
            if 'seed' in instance.tags.get('type', ''):
                seeds.append(instance.private_ip_address)

    return ", ".join(seeds)

def main(options, destination):
    if not (options.aws_secret_key and options.aws_access_key):
        return

    os.environ['AWS_ACCESS_KEY_ID'] = options.aws_access_key
    os.environ['AWS_SECRET_ACCESS_KEY'] = options.aws_secret_key

    s3conn = boto.connect_s3()
    template_url = s3conn.generate_url(10, "GET", "bucket", "/config/cassandraconf.tmpl")
    template = urllib.urlopen(template_url).read()
    
    conn = ec2.connect_to_region(region_name="us-west-1")
    me = conn.get_all_instances([options.instance])[0].instances[0]

    filling = dict(me.tags)
    filling['hostname'] = me.private_ip_address
    filling['seeds'] = get_seeds(conn, me.tags.get('cluster'))
    
    if 'brisk' in me.tags.get('type', ''):
        open('/etc/default/brisk', 'wb').write("\nHADOOP_ENABLED=1\n")

    filled_template = template % filling

    open(destination, 'wb').write(filled_template)
        
if __name__ == '__main__':
    """
    e.g, cassandra_configure.py --secret=<SECRET_KEY> --api=<API_KEY>
    """
    from optparse import OptionParser

    usage = "usage: %prog [options] <final config destination path>"
    parser = OptionParser(usage=usage)

    parser.add_option("--secret", action="store", dest="aws_secret_key",
                       default=os.environ.get('AWS_SECRET_ACCESS_KEY'), help="AWS Secret Access Key")
    parser.add_option("--api", action="store", dest="aws_access_key",
                       default=os.environ.get('AWS_ACCESS_KEY_ID'), help="AWS Access Key")
    parser.add_option("--instance", action="store", dest="instance",
                       default=os.environ.get('INSTANCE_ID'), help="Instance ID of the current instance")
    
    (options, args) = parser.parse_args()

    if len(args) != 1:
        raise Exception("Need one location for final configuration file destination")

    main(options, args[0])