docker-compose/compose/config/sort_services.py

from compose.config.errors import DependencyError


def get_service_name_from_net(net_config):
    if not net_config:
        return

    if not net_config.startswith('container:'):
        return

    _, net_name = net_config.split(':', 1)
    return net_name


def sort_service_dicts(services):
    # Topological sort (Cormen/Tarjan algorithm).
    unmarked = services[:]
    temporary_marked = set()
    sorted_services = []

    def get_service_names(links):
        return [link.split(':')[0] for link in links]

    def get_service_names_from_volumes_from(volumes_from):
        return [volume_from.source for volume_from in volumes_from]

    def get_service_dependents(service_dict, services):
        name = service_dict['name']
        return [
            service for service in services
            if (name in get_service_names(service.get('links', [])) or
                name in get_service_names_from_volumes_from(service.get('volumes_from', [])) or
                name == get_service_name_from_net(service.get('net')))
        ]

    def visit(n):
        if n['name'] in temporary_marked:
            if n['name'] in get_service_names(n.get('links', [])):
                raise DependencyError('A service can not link to itself: %s' % n['name'])
            if n['name'] in n.get('volumes_from', []):
                raise DependencyError('A service can not mount itself as volume: %s' % n['name'])
            else:
                raise DependencyError('Circular import between %s' % ' and '.join(temporary_marked))
        if n in unmarked:
            temporary_marked.add(n['name'])
            for m in get_service_dependents(n, services):
                visit(m)
            temporary_marked.remove(n['name'])
            unmarked.remove(n)
            sorted_services.insert(0, n)

    while unmarked:
        visit(unmarked[-1])

    return sorted_services