# Parse up the command line arguments.

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

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

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

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

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

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

args = parser.parse_args()

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

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

instances = get_running_instances(autoscaling_groups=args.autoscaling_group)

# Generate the new config from the template.

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

new_configuration = generate_haproxy_config(template=args.template,

instances=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(filename=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logging.info('Existing configuration is outdated.')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(filename=args.output,

content=generate_haproxy_config(template=args.template, instances=instances))

# Get PID if haproxy is already running.

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

pid = file_contents(filename=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: