Python fabric.api.env 模块，roledefs() 实例源码

def chef_query(query, api=None, hostname_attr=DEFAULT_HOSTNAME_ATTR, environment=_default_environment):
    """A decorator to use an arbitrary Chef search query to find nodes to execute on.

    This is used like Fabric's ``roles()`` decorator, but accepts a Chef search query.

    Example::

        from chef.fabric import chef_query

        @chef_query('roles:web AND tags:active')
        @task
        def deploy():
            pass

    .. versionadded:: 0.2.1
    """
    api = _api(api)
    if api.version_parsed < Environment.api_version_parsed and environment is not None:
        raise ChefAPIVersionError('Environment support requires Chef API 0.10 or greater')
    rolename = 'query_'+query
    env.setdefault('roledefs', {})[rolename] = Roledef(query, api, hostname_attr, environment)
    return lambda fn: roles(rolename)(fn)

def get_effective_role():
    """Acquire the role definition according to current host
    """
    for role in env.roles:
        if env.host in env.roledefs[role]['hosts']:
            return role, env.roledefs[role]
    raise ValueError('Role undefined by {}'.format(env.host))

def chef_environment(name, api=None):
    """A Fabric task to set the current Chef environment context.

    This task works alongside :func:`~chef.fabric.chef_roledefs` to set the
    Chef environment to be used in future role queries.

    Example::

        from chef.fabric import chef_environment, chef_roledefs
        env.roledefs = chef_roledefs()

    .. code-block:: bash

        $ fab env:production deploy

    The task can be configured slightly via Fabric ``env`` values.

    ``env.chef_environment_task_alias`` sets the task alias, defaulting to "env".
    This value must be set **before** :mod:`chef.fabric` is imported.

    ``env.chef_environment_validate`` sets if :class:`~chef.Environment` names
    should be validated before use. Defaults to True.

    .. versionadded:: 0.2
    """
    if env.get('chef_environment_validate', True):
        api = _api(api)
        chef_env = Environment(name, api=api)
        if not chef_env.exists:
            raise ChefError('Unknown Chef environment: %s' % name)
    env['chef_environment'] = name

def chef_roledefs(api=None, hostname_attr=DEFAULT_HOSTNAME_ATTR, environment=_default_environment):
    """Build a Fabric roledef dictionary from a Chef server.

    Example::

        from fabric.api import env, run, roles
        from chef.fabric import chef_roledefs

        env.roledefs = chef_roledefs()

        @roles('web_app')
        def mytask():
            run('uptime')

    ``hostname_attr`` can either be a string that is the attribute in the chef
    node that holds the hostname or IP to connect to, an array of such keys to
    check in order (the first which exists will be used), or a callable which
    takes a :class:`~chef.Node` and returns the hostname or IP to connect to.

    To refer to a nested attribute, separate the levels with ``'.'`` e.g. ``'ec2.public_hostname'``

    ``environment`` is the Chef :class:`~chef.Environment` name in which to
    search for nodes. If set to ``None``, no environment filter is added. If
    set to a string, it is used verbatim as a filter string. If not passed as
    an argument at all, the value in the Fabric environment dict is used,
    defaulting to ``'_default'``.

    .. note::

        ``environment`` must be set to ``None`` if you are emulating Chef API
        version 0.9 or lower.

    .. versionadded:: 0.1

    .. versionadded:: 0.2
        Support for iterable and callable values for  the``hostname_attr``
        argument, and the ``environment`` argument.
    """
    api = _api(api)
    if api.version_parsed < Environment.api_version_parsed and environment is not None:
        raise ChefAPIVersionError('Environment support requires Chef API 0.10 or greater')
    roledefs = {}
    for row in Search('role', api=api):
        name = row['name']
        roledefs[name] =  Roledef('roles:%s' % name, api, hostname_attr, environment)
    return roledefs