# Parse up the command line arguments.

parser = argparse.ArgumentParser(description='Update haproxy to use all instances running in a security group.')

parser.add_argument('--config', default="/etc/haproxy-autoscale/haproxy-autoscale.conf",

help='Path to the config file.')

parser.add_argument('--autoscaling-group', required=True, nargs='+', type=str)

parser.add_argument('--region', default="us-east-1", help="AWS region name")

parser.add_argument('--output', default='/etc/haproxy/haproxy.cfg',

help='Defaults to haproxy.cfg if not specified.')

parser.add_argument('--template', default='/etc/haproxy-autoscale/haproxy.tpl')

parser.add_argument('--haproxy', default='/usr/sbin/haproxy',

help='The haproxy binary to call. Defaults to haproxy if not specified.')

parser.add_argument('--pid', default='/var/run/haproxy.pid',

help='The pid file for haproxy. Defaults to /var/run/haproxy.pid.')

parser.add_argument('--eip',

help='The Elastic IP to bind to when VIP seems unhealthy.')

parser.add_argument('--health-check-url',

help='The URL to check. Assigns EIP to self if health check fails.')

args = parser.parse_args()

# haproxy-autoscale config file

config_fh = open(args.config, "ro")

config = configparser.RawConfigParser()

config.read_file(config_fh)

config_fh.close()

access_key = config.get("credential", "access_key")

secret_key = config.get("credential", "secret_key")

# Fetch a list of all the instances in these security groups.

instances = {}

for autoscaling_group in args.autoscaling_group:

logging.info('Getting instances for %s.' % autoscaling_group)

instances[autoscaling_group] = list_as_instances(access_key, secret_key, args.region,

autoscaling_group)

# Generate the new config from the template.

logging.info('Generating configuration for haproxy.')

new_configuration = generate_haproxy_config(args.template, instances)

# See if this new config is different. If it is then restart using it.

# Otherwise just delete the temporary file and do nothing.

logging.info('Comparing to existing configuration.')

old_configuration = file_contents(args.output)

if new_configuration != old_configuration:

logging.info('Existing configuration is outdated.')

# Overwite the existing config file.

logging.info('Writing new configuration.')

file_contents(args.output, generate_haproxy_config(args.template, instances))

# Get PID if haproxy is already running.

logging.info('Fetching PID from %s.' % args.pid)

pid = file_contents(args.pid)

# Restart haproxy.

logging.info('Restarting haproxy.')

command = '''%s -p %s -f %s -sf %s''' % (args.haproxy, args.pid, args.output, pid or '')

logging.info('Executing: %s' % command)

subprocess.call(command, shell=True)

else:

logging.info('Configuration unchanged. Skipping restart.')

# Do a health check on the url if specified.

try:

if args.health_check_url and args.eip:

logging.info('Performing health check.')

try:

logging.info('Checking %s' % args.health_check_url)

response = urllib2.urlopen(args.health_check_url)

logging.info('Response: %s' % response.read())

except:

# Assign the EIP to self.

logging.warn('Health check failed. Assigning %s to self.' % args.eip)

steal_elastic_ip(access_key, secret_key, args.eip)

except: