Quick script to spawn a CoreOS cluster using spot instances on EC2 for playing

cloud_config.yml

#cloud-config
coreos:
  etcd:
    discovery: https://discovery.etcd.io/fancy
    addr: $public_ipv4:4001
    peer-addr: $private_ipv4:7001
  fleet:
      public-ip: $public_ipv4
  units:
    - name: etcd.service
      command: start
    - name: fleet.service
      command: start

    - name: format-ephemeral.service
      command: start
      content: |
        [Unit]
        Description=Stripes the ephemeral instance disks to one btrfs volume
        [Service]
        Type=oneshot
        RemainAfterExit=yes
        ExecStart=/usr/sbin/wipefs -f /dev/xvdb /dev/xvdc
        ExecStart=/usr/sbin/mkfs.btrfs -f -d raid0 /dev/xvdb /dev/xvdc

    - name: var-lib-docker.mount
      command: start
      content: |
        [Unit]
        Description=Mount ephemeral to /var/lib/docker
        Requires=format-ephemeral.service
        After=format-ephemeral.service
        Before=docker.service
        [Mount]
        What=/dev/xvdb
        Where=/var/lib/docker
        Type=btrfs

spawn_coreos_cluster.py

#!/usr/bin/env python

import argparse
import os
import sys
import time

from boto import ec2
from boto.ec2.blockdevicemapping import BlockDeviceMapping, BlockDeviceType



if not os.environ.get('AWS_SECRET_KEY'):
    err = 'No AWS credentials present in the environment, try again...'
    raise SystemExit(err)


INSTANCE_TYPE = 'c3.xlarge'
INSTANCE_BID = '0.05'

COREOS_AMI = 'ami-31222974'

AWS_ACCESS_KEY = os.environ.get('AWS_ACCESS_KEY')
AWS_SECRET_KEY = os.environ.get('AWS_SECRET_KEY')
EC2_KEY_NAME = 'jake'
SECURITY_GROUPS = ['sg-1234']


def parse_args():
    ap = argparse.ArgumentParser(description='Spawn a CoreOS cluster')
    ap.add_argument('-r', '--region', default='us-west-1')
    ap.add_argument('-n', '--node-count',
                    type=int,
                    default=3,
                    help='How many nodes should be in the cluster?')
    args = ap.parse_args()

    return args


def _get_cloudconfig():
    base_path = os.path.dirname(os.path.realpath(__file__))
    cloud_config = open(os.path.join(base_path, 'cloud_config.yml'))
    return cloud_config.read()

def spawn_cluster(count, region):
    conn = ec2.connect_to_region(region,
                                 aws_access_key_id=AWS_ACCESS_KEY,
                                 aws_secret_access_key=AWS_SECRET_KEY)

    mapping = BlockDeviceMapping()
    eph0 = BlockDeviceType(ephemeral_name='ephemeral0')
    eph1 = BlockDeviceType(ephemeral_name='ephemeral1')
    mapping['/dev/xvdb'] = eph0
    mapping['/dev/xvdc'] = eph1

    instance_params = {
        'count': count,
        'key_name': EC2_KEY_NAME,
        'user_data': _get_cloudconfig(),
        'instance_type': INSTANCE_TYPE,
        'block_device_map': mapping,
        'security_group_ids': SECURITY_GROUPS
    }

    spot_reqs = conn.request_spot_instances(INSTANCE_BID, COREOS_AMI, **instance_params)
    for req in spot_reqs:
        req.add_tags({'Name': 'coreos-cluster', 'coreos': True})
    spot_ids = [s.id for s in spot_reqs]

    for x in xrange(50):
        print 'Waiting for instances to spawn...'
        spot_reqs = conn.get_all_spot_instance_requests(request_ids=spot_ids)
        instance_ids = [s.instance_id for s in spot_reqs if s.instance_id != None]
        if len(instance_ids) == len(spot_reqs):
            print 'Instances all spawned'
            print '====================='
            for i in conn.get_only_instances(instance_ids=instance_ids):
                print 'CoreOS Node:'
                print '    - spot req id: %s' % i.spot_instance_request_id
                print '    - instance id: %s' % i.id
                print '    - Public IP: %s' % i.ip_address
                print '    - Public DNS: %s' % i.public_dns_name
            break

        time.sleep(10)


if __name__ == '__main__':
    args = parse_args()
    spawn_cluster(args.node_count, args.region)

stdout

➜  core  ./spawn_coreos_cluster.py -n 3
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Waiting for instances to spawn...
Instances all spawned
=====================
CoreOS Node:
    - spot req id: sir-03rt1m
    - instance id: i-ead754
    - Public IP: 54.183.220.1
    - Public DNS: ec2-54-183-220-1.us-west-1.compute.amazonaws.com
CoreOS Node:
    - spot req id: sir-03rw5q
    - instance id: i-cfd053
    - Public IP: 54.183.178.2
    - Public DNS: ec2-54-183-178-2.us-west-1.compute.amazonaws.com
CoreOS Node:
    - spot req id: sir-03rwp8
    - instance id: i-45d053
    - Public IP: 54.183.218.3
    - Public DNS: ec2-54-183-218-3.us-west-1.compute.amazonaws.com