cs.app.flag 20170906

Persistent filesystem based flags for state and control.

Filesystem visible boolean flags for control and status, allowing easy monitoring of services or other status, and control by flag management for programmes which also monitor the flags.

The flags are expressed as individual files with uppercase names in a common directory ($HOME/var/flags by default); an empty or missing file is “false” and a nonempty file is “true”.

The Flags class provides easy Pythonic access. If presents as a modifiable mapping whose keys are the flag names.

The is also a FlaggedMixin class providing convenient methods and attributes for maintaining a collection of flags associated with some object with flag names prefixed by the object’s .name attribute uppercased and with an underscore appended:

class SvcD(...,FlaggedMixin):
  def __init__(self, name, ...)
    self.name = name
    FlaggedMixin.__init__(self)
    ...
  def disable(self):
    self.flag_disabled = True
  def restart(self):
    self.flag_restart = True
  def _restart(self):
    self.flag_restart = False
    ... restart the SvcD ...