ansible/modules/system/svc.py

NB: extending the Svc module has been abandoned in favour of a separate Nosh module. In fact, splitting the Service module is the current Ansible project.

This is an attempt to extend the svc module for managing daemontools by adding a subclass to control nosh (and possibly other daemontools family toolsets).

The module as it is (https://github.com/ansible/ansible/commit/eb1214baad0cbe2c4b7304caebb9ae1c7dc0d8db) offers to subclass the Svc class with the help of the _load_dist_subclass function which checks for the distro parameter.

If activated, this mechanism fails because the expression to obtain the distro parameter is incorrect:

def _load_dist_subclass(cls, *args, **kwargs):
    '''
    Used for derivative implementations
    '''
    subclass = None

    distro = kwargs['module'].params['distro'] # this assignment fails with a KeyError

    # get the most specific superclass for this platform
    if distro is not None:
        for sc in cls.__subclasses__():
            if sc.distro is not None and sc.distro == distro:
                subclass = sc
    if subclass is None:
        subclass = cls

return super(cls, subclass).__new__(subclass)

The following assignment works but is rather cryptic and there is presumably a more straightforward way to obtain the passed-in distro parameter:

distro = args[0][0].params['distro]

The solution adopted here is to simplify the function signature, making it more readable, since only one argument is given to the Svc instance (svc = Svc(module)):

def _load_dist_subclass(cls, module):
    ...
    distro = module.params['distro']

Subclasses can then define a distro attribute and the mechanism works.

minor corrections

The distro parameter referred to in _load_dist_subclass is actually called dist in the AnsibleModule argument_spec

The distro parameter is not mentionned in the documentation.

The killed state is mentionned in the documentation but not listed as possible state.

The state -> method correspondence has needless indirection. Methods are now named after the expected state directly.

Daemontools' svc doesn't have a -1 option for the SIGUSR1 signal, it has been replaced by -h for SIGHUP, which is also the more usual reloading signal. However, this changes the interface.

usage

- svc:
    name: sshd
    state: started
    distro: nosh