gistfile1.txt

#!/usr/bin/env python
import base64
import json
import os
import re
import yaml


YAML_CONFIG_FILE = os.environ.get('APPLICATION_CONFIG')
with open(YAML_CONFIG_FILE, 'r') as YAML_CONFIG:
    APP_CONFIG = yaml.load(YAML_CONFIG)

with open('scripts/ami_lookup.yaml', 'r') as YAML_AMI:
    AMI_DICT = yaml.load(YAML_AMI)

ENVIRONMENT = APP_CONFIG['environment']
AMI_NAME = APP_CONFIG['ami_name']

CONFIG = {}

CONFIG['image_id'] = AMI_DICT[ENVIRONMENT][AMI_NAME]

# grab 'spinners' from 'applications/spinners/production.yaml'
CONFIG['application_name'] = os.environ.get('APPLICATION_CONFIG').split('/')[-2]
CONFIG['environment'] = ENVIRONMENT

# tags
APP_CONFIG.setdefault('tags', {})
APP_CONFIG['tags']['environment'] = ENVIRONMENT
APP_CONFIG['tags']['Name'] = CONFIG['application_name']

# get the revision
if not os.environ.get('REVISION') or os.environ.get('REVISION', '').lower() == '${revision}':
    raise Exception('Missing REVISION environment variable for this build.')

# build userdata
userdata = """export REVISION={revision}
export TAGS='{tags}'
export APPLICATION_NAME={app_name}
{userdata}""".format(
    revision=os.environ.get('REVISION'),
    tags=json.dumps(APP_CONFIG['tags']),
    app_name=CONFIG['application_name'],
    userdata=APP_CONFIG.get('userdata', '')
)

"""
Replace placeholder values in userdata.
Assuming: os.environ['REVISION'] = 123
"BUILD_NUMBER=%%REVISION%%" becomes "BUILD_NUMBER=123"
"""
for placeholder in re.findall(r'%%(.*)%%', userdata):
    userdata = re.sub(r'%%{0}%%'.format(placeholder), os.environ.get(placeholder), userdata)

CONFIG['base64_userdata'] = base64.b64encode(userdata)

print yaml.dump(CONFIG)