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#!/usr/bin/python
'''This script configures and starts a local haproxy instances, bound to
127.0.0.1, that forwards connections all of the discovered
docker/kubernetes environment variables.'''
import argparse
import os
import sys
from jinja2 import Environment, FileSystemLoader
import re
import urlparse
re_url = re.compile(
'^(?P<name>.*)_PORT_(?P<port>\d+)_(?P<proto>(UDP|TCP))$')
def parse_args():
p = argparse.ArgumentParser()
p.add_argument('--output', '-o',
default='/etc/haproxy/haproxy.cfg')
p.add_argument('--no-start', '-n',
action='store_true')
p.add_argument('--template-dir', '-t',
default='/etc/haproxy/templates')
return p.parse_args()
def discover_services():
services = []
for k in os.environ:
mo = re_url.match(k)
if mo:
parts = urlparse.urlparse(os.environ[k])
remote_host,remote_port = parts.netloc.split(':')
service_name = '%(name)s-%(port)s' % mo.groupdict()
services.append({
'remote_name': mo.group('name'),
'remote_addr': remote_host,
'remote_port': remote_port,
'remote_proto': parts.scheme,
'local_port': mo.group('port'),
'service_name': service_name,
})
return services
def main():
args = parse_args()
services = discover_services()
env = Environment(loader=FileSystemLoader(['.',
args.template_dir]))
template = env.get_template('haproxy.cfg.tmpl')
with open(args.output, 'w') as fd:
fd.write(template.render(services=services))
if args.no_start:
return
os.execlp('haproxy', 'haproxy', '-f', args.output, '-db')
if __name__ == '__main__':
main()
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