traefik_hosts

#!/usr/bin/env python3
import os
import sys
import docker
import socket
import logging
import argparse


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('-o', '--output', default='/etc/traefik_hosts')
    parser.add_argument('-v', '--verbose', action='store_true', default=False)
    args = parser.parse_args()

    logging.basicConfig(
        stream=sys.stderr,
        format='%(levelname)s: %(message)s',
        level=100000,
    )
    log = logging.getLogger('wait_for_services')
    log.setLevel(logging.DEBUG if args.verbose else logging.INFO)

    my_id = socket.gethostname()

    client = docker.from_env()

    label = None
    for container in client.containers.list(all=True):
        if container.id.startswith(my_id):
            if 'com.docker.compose.project' in container.labels:
                label = (
                    'com.docker.compose.project=%s'
                ) % container.labels['com.docker.compose.project']
                break

    if label is None:
        log.critical(
            'Cant find my project! Are you using me inside compose ?!')
        return 1

    containers = client.containers.list(filters={'label': label}, all=True)
    containers = {
        c.labels['com.docker.compose.service']: c
        for c in containers
    }

    domains = set()

    for service in list(containers):
        container = containers[service]
        if container.id.startswith(my_id):
            containers.pop(service)
            continue
        for label, value in container.labels.items():
            if label.startswith('traefik') and 'Host' in value:
                if 'Host:' in value:
                    # v1
                    value = value.split('Host:', 1)[1]
                    value = value.split(';', 1)[0]
                elif 'Host(' in value:
                    # v2
                    value = value.split('Host(', 1)[1]
                    value = value.split(')', 1)[0]
                    value = value.replace('`', '')
                for name in value.split(','):
                    domains.add(name)

    with open('/etc/hosts') as fd:
        line = fd.readlines()[-1]

    host = line.split()[0]

    if os.path.isfile(args.output):
        mode = 'a+'
    else:
        mode = 'w'

    new_line = '{0} {1}'.format(host,  ' '.join(sorted(list(domains))))
    with open(args.output, mode) as fd:
        fd.seek(0)
        fd.truncate()
        fd.write('127.0.0.1 localhost\n{0}\n'.format(new_line))
    with open(args.output) as fd:
        print(fd.read())
    return 0


if __name__ == '__main__':
    sys.exit(main())