diff options
Diffstat (limited to 'sleekxmpp/xmlstream/statemachine.py')
| -rw-r--r-- | sleekxmpp/xmlstream/statemachine.py | 245 |
1 files changed, 210 insertions, 35 deletions
diff --git a/sleekxmpp/xmlstream/statemachine.py b/sleekxmpp/xmlstream/statemachine.py index fb7d1508..67b514a2 100644 --- a/sleekxmpp/xmlstream/statemachine.py +++ b/sleekxmpp/xmlstream/statemachine.py @@ -7,53 +7,228 @@ """ from __future__ import with_statement import threading +import time +import logging + class StateMachine(object): - def __init__(self, states=[], groups=[]): - self.lock = threading.Lock() - self.__state = {} - self.__default_state = {} - self.__group = {} + def __init__(self, states=[]): + self.lock = threading.Condition(threading.RLock()) + self.__states= [] self.addStates(states) - self.addGroups(groups) + self.__default_state = self.__states[0] + self.__current_state = self.__default_state def addStates(self, states): with self.lock: for state in states: - if state in self.__state or state in self.__group: - raise IndexError("The state or group '%s' is already in the StateMachine." % state) - self.__state[state] = states[state] - self.__default_state[state] = states[state] + if state in self.__states: + raise IndexError("The state '%s' is already in the StateMachine." % state) + self.__states.append( state ) - def addGroups(self, groups): - with self.lock: - for gstate in groups: - if gstate in self.__state or gstate in self.__group: - raise IndexError("The key or group '%s' is already in the StateMachine." % gstate) - for state in groups[gstate]: - if state in self.__state: - raise IndexError("The group %s contains a key %s which is not set in the StateMachine." % (gstate, state)) - self.__group[gstate] = groups[gstate] - - def set(self, state, status): + + def transition(self, from_state, to_state, wait=0.0, func=None, args=[], kwargs={} ): + ''' + Transition from the given `from_state` to the given `to_state`. + This method will return `True` if the state machine is now in `to_state`. It + will return `False` if a timeout occurred the transition did not occur. + If `wait` is 0 (the default,) this method returns immediately if the state machine + is not in `from_state`. + + If you want the thread to block and transition once the state machine to enters + `from_state`, set `wait` to a non-negative value. Note there is no 'block + indefinitely' flag since this leads to deadlock. If you want to wait indefinitely, + choose a reasonable value for `wait` (e.g. 20 seconds) and do so in a while loop like so: + + :: + + while not thread_should_exit and not state_machine.transition('disconnected', 'connecting', wait=20 ): + pass # timeout will occur every 20s unless transition occurs + if thread_should_exit: return + # perform actions here after successful transition + + This allows the thread to be responsive by setting `thread_should_exit=True`. + + The optional `func` argument allows the user to pass a callable operation which occurs + within the context of the state transition (e.g. while the state machine is locked.) + If `func` returns a True value, the transition will occur. If `func` returns a non- + True value or if an exception is thrown, the transition will not occur. Any thrown + exception is not caught by the state machine and is the caller's responsibility to handle. + If `func` completes normally, this method will return the value returned by `func.` If + values for `args` and `kwargs` are provided, they are expanded and passed like so: + `func( *args, **kwargs )`. + ''' + + return self.transition_any( (from_state,), to_state, wait=wait, + func=func, args=args, kwargs=kwargs ) + + + def transition_any(self, from_states, to_state, wait=0.0, func=None, args=[], kwargs={} ): + ''' + Transition from any of the given `from_states` to the given `to_state`. + ''' + + if not (isinstance(from_states,tuple) or isinstance(from_states,list)): + raise ValueError( "from_states should be a list or tuple" ) + + for state in from_states: + if not state in self.__states: + raise ValueError( "StateMachine does not contain from_state %s." % state ) + if not to_state in self.__states: + raise ValueError( "StateMachine does not contain to_state %s." % to_state ) + with self.lock: - if state in self.__state: - self.__state[state] = bool(status) + start = time.time() + while not self.__current_state in from_states: + # detect timeout: + if time.time() >= start + wait: return False + self.lock.wait(wait) + + if self.__current_state in from_states: # should always be True due to lock + + return_val = True + # Note that func might throw an exception, but that's OK, it aborts the transition + if func is not None: return_val = func(*args,**kwargs) + + # some 'false' value returned from func, + # indicating that transition should not occur: + if not return_val: return return_val + + logging.debug(' ==== TRANSITION %s -> %s', self.__current_state, to_state) + self.__current_state = to_state + self.lock.notify_all() + return return_val # some 'true' value returned by func or True if func was None else: - raise KeyError("StateMachine does not contain state %s." % state) - - def __getitem__(self, key): - if key in self.__group: - for state in self.__group[key]: - if not self.__state[state]: - return False - return True - return self.__state[key] + logging.error( "StateMachine bug!! The lock should ensure this doesn't happen!" ) + return False + + + def transition_ctx(self, from_state, to_state, wait=0.0): + ''' + Use the state machine as a context manager. The transition occurs on /exit/ from + the `with` context, so long as no exception is thrown. For example: + + :: + + with state_machine.transition_ctx('one','two', wait=5) as locked: + if locked: + # the state machine is currently locked in state 'one', and will + # transition to 'two' when the 'with' statement ends, so long as + # no exception is thrown. + print 'Currently locked in state one: %s' % state_machine['one'] + + else: + # The 'wait' timed out, and no lock has been acquired + print 'Timed out before entering state "one"' + + print 'Since no exception was thrown, we are now in state "two": %s' % state_machine['two'] + + + The other main difference between this method and `transition()` is that the + state machine is locked for the duration of the `with` statement. Normally, + after a `transition()` occurs, the state machine is immediately unlocked and + available to another thread to call `transition()` again. + ''' + + if not from_state in self.__states: + raise ValueError( "StateMachine does not contain from_state %s." % from_state ) + if not to_state in self.__states: + raise ValueError( "StateMachine does not contain to_state %s." % to_state ) + + return _StateCtx(self, from_state, to_state, wait) + - def __getattr__(self, attr): - return self.__getitem__(attr) + def ensure(self, state, wait=0.0): + ''' + Ensure the state machine is currently in `state`, or wait until it enters `state`. + ''' + return self.ensure_any( (state,), wait=wait ) + + + def ensure_any(self, states, wait=0.0): + ''' + Ensure we are currently in one of the given `states` + ''' + if not (isinstance(states,tuple) or isinstance(states,list)): + raise ValueError('states arg should be a tuple or list') + + for state in states: + if not state in self.__states: + raise ValueError( "StateMachine does not contain state '%s'" % state ) + + with self.lock: + start = time.time() + while not self.__current_state in states: + # detect timeout: + if time.time() >= start + wait: return False + self.lock.wait(wait) + return self.__current_state in states # should always be True due to lock + def reset(self): - self.__state = self.__default_state + # TODO need to lock before calling this? + self.transition(self.__current_state, self._default_state) + + + def _set_state(self, state): #unsynchronized, only call internally after lock is acquired + self.__current_state = state + return state + + + def current_state(self): + ''' + Return the current state name. + ''' + return self.__current_state + + + def __getitem__(self, state): + ''' + Non-blocking, non-synchronized test to determine if we are in the given state. + Use `StateMachine.ensure(state)` to wait until the machine enters a certain state. + ''' + return self.__current_state == state + + def __str__(self): + return "".join(( "StateMachine(", ','.join(self.__states), "): ", self.__current_state )) + + + +class _StateCtx: + + def __init__( self, state_machine, from_state, to_state, wait ): + self.state_machine = state_machine + self.from_state = from_state + self.to_state = to_state + self.wait = wait + self._timeout = False + + def __enter__(self): + self.state_machine.lock.acquire() + start = time.time() + while not self.state_machine[ self.from_state ]: + # detect timeout: + if time.time() >= start + self.wait: + logging.debug('StateMachine timeout while waiting for state: %s', self.from_state ) + self._timeout = True # to indicate we should not transition + return False + self.state_machine.lock.wait(self.wait) + + logging.debug('StateMachine entered context in state: %s', + self.state_machine.current_state() ) + return True + + def __exit__(self, exc_type, exc_val, exc_tb): + if exc_val is not None: + logging.exception( "StateMachine exception in context, remaining in state: %s\n%s:%s", + self.state_machine.current_state(), exc_type.__name__, exc_val ) + elif not self._timeout: + logging.debug(' ==== TRANSITION %s -> %s', + self.state_machine.current_state(), self.to_state) + self.state_machine._set_state( self.to_state ) + + self.state_machine.lock.notify_all() + self.state_machine.lock.release() + return False # re-raise any exception |