From 2f0f18a8c62db21fa3ba8cc87a6d190aca205c30 Mon Sep 17 00:00:00 2001 From: Thom Nichols Date: Thu, 3 Jun 2010 08:07:56 -0400 Subject: added function to retrieve the current state --- sleekxmpp/xmlstream/statemachine.py | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'sleekxmpp/xmlstream/statemachine.py') diff --git a/sleekxmpp/xmlstream/statemachine.py b/sleekxmpp/xmlstream/statemachine.py index c5f51765..065d5794 100644 --- a/sleekxmpp/xmlstream/statemachine.py +++ b/sleekxmpp/xmlstream/statemachine.py @@ -110,7 +110,14 @@ class StateMachine(object): def reset(self): # TODO need to lock before calling this? self.transition(self.__current_state, self._default_state) - + + + def current_state(self): + ''' + Return the current state name. + ''' + return self.__current_state + def __getitem__(self, state): ''' -- cgit v1.2.3 From f54501a3465b84f1be157c1ba99df854dbeaed1d Mon Sep 17 00:00:00 2001 From: Thom Nichols Date: Thu, 3 Jun 2010 14:12:06 -0400 Subject: added function execution on transition, and more unit tests. --- sleekxmpp/xmlstream/statemachine.py | 30 +++++++++++++++++++++++++----- 1 file changed, 25 insertions(+), 5 deletions(-) (limited to 'sleekxmpp/xmlstream/statemachine.py') diff --git a/sleekxmpp/xmlstream/statemachine.py b/sleekxmpp/xmlstream/statemachine.py index 065d5794..0c841a9f 100644 --- a/sleekxmpp/xmlstream/statemachine.py +++ b/sleekxmpp/xmlstream/statemachine.py @@ -10,6 +10,7 @@ import threading import time import logging + class StateMachine(object): def __init__(self, states=[]): @@ -27,7 +28,7 @@ class StateMachine(object): self.__states.append( state ) - def transition(self, from_state, to_state, wait=0.0): + 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 @@ -47,12 +48,22 @@ class StateMachine(object): if thread_should_exit: return # perform actions here after successful transition - This allows the thread to be interrupted by setting `thread_should_exit=True` + 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 ) + 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): + 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`. ''' @@ -73,10 +84,19 @@ class StateMachine(object): 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.notifyAll() - return True + return return_val # some 'true' value returned by func or True if func was None else: logging.error( "StateMachine bug!! The lock should ensure this doesn't happen!" ) return False -- cgit v1.2.3 From 66cf0c20218657622a5d98aee155df1ea37d9a89 Mon Sep 17 00:00:00 2001 From: Thom Nichols Date: Mon, 7 Jun 2010 13:16:02 -0400 Subject: context manager is working but there's a fatal flaw: inside the body of the 'with' statement, there's no way to tell whether or not the transition occurred or timed out. --- sleekxmpp/xmlstream/statemachine.py | 83 +++++++++++++++++++++++++++++-------- 1 file changed, 65 insertions(+), 18 deletions(-) (limited to 'sleekxmpp/xmlstream/statemachine.py') diff --git a/sleekxmpp/xmlstream/statemachine.py b/sleekxmpp/xmlstream/statemachine.py index 0c841a9f..51b4aaed 100644 --- a/sleekxmpp/xmlstream/statemachine.py +++ b/sleekxmpp/xmlstream/statemachine.py @@ -63,20 +63,22 @@ class StateMachine(object): 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`. ''' - with self.lock: - for state in from_states: - if isinstance(state,tuple) or isinstance(state,list): - raise ValueError( "State %s should be a string. Did you mean to call 'StateMachine.transition_any()?" % str(state) ) - 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 ) + 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: start = time.time() while not self.__current_state in from_states: # detect timeout: @@ -102,23 +104,34 @@ class StateMachine(object): return False + def transition_ctx(self, from_state, to_state, wait=0.0): + if not from_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 ) + + return _StateCtx(self, from_state, to_state, wait) + + 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` ''' - with self.lock: - for state in states: - if isinstance(state,tuple) or isinstance(state,list): - raise ValueError( "State %s should be a string. Did you mean to call 'StateMachine.transition_any()?" % str(state) ) - if not state in self.__states: - raise ValueError( "StateMachine does not contain state %s." % state ) + 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: @@ -132,6 +145,11 @@ class StateMachine(object): 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. @@ -146,12 +164,41 @@ class StateMachine(object): ''' return self.__current_state == 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.lock.acquire() - return 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 + break + self.state_machine.lock.wait(self.wait) + + logging.debug('StateMachine entered context in state: %s', + self.state_machine.current_state() ) + return self.state_machine def __exit__(self, exc_type, exc_val, exc_tb): - self.lock.nofityAll() - self.lock.release() + 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.notifyAll() + self.state_machine.lock.release() return False # re-raise any exception -- cgit v1.2.3 From 47f1fb16909d3baaec5822b1dcbca89491d0d18c Mon Sep 17 00:00:00 2001 From: Thom Nichols Date: Mon, 7 Jun 2010 13:43:37 -0400 Subject: context manager now returns a boolean 'result' as the context variable to indicate whether the transition timed out or if you are actually locked when entering the context body --- sleekxmpp/xmlstream/statemachine.py | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'sleekxmpp/xmlstream/statemachine.py') diff --git a/sleekxmpp/xmlstream/statemachine.py b/sleekxmpp/xmlstream/statemachine.py index 51b4aaed..b1ab7574 100644 --- a/sleekxmpp/xmlstream/statemachine.py +++ b/sleekxmpp/xmlstream/statemachine.py @@ -182,12 +182,12 @@ class _StateCtx: 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 - break + return False self.state_machine.lock.wait(self.wait) logging.debug('StateMachine entered context in state: %s', self.state_machine.current_state() ) - return self.state_machine + return True def __exit__(self, exc_type, exc_val, exc_tb): if exc_val is not None: -- cgit v1.2.3 From 9464736551311c015f1511e7535c762923838eaf Mon Sep 17 00:00:00 2001 From: Thom Nichols Date: Mon, 7 Jun 2010 13:58:15 -0400 Subject: added __str__ --- sleekxmpp/xmlstream/statemachine.py | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'sleekxmpp/xmlstream/statemachine.py') diff --git a/sleekxmpp/xmlstream/statemachine.py b/sleekxmpp/xmlstream/statemachine.py index b1ab7574..704cabdb 100644 --- a/sleekxmpp/xmlstream/statemachine.py +++ b/sleekxmpp/xmlstream/statemachine.py @@ -163,6 +163,10 @@ class StateMachine(object): 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: -- cgit v1.2.3 From 34dc236126d272a16df0915b010dca0e2e38f0d4 Mon Sep 17 00:00:00 2001 From: Thom Nichols Date: Mon, 7 Jun 2010 14:41:42 -0400 Subject: added documentation for transition_ctx and removed some superfluous comment lines --- sleekxmpp/xmlstream/statemachine.py | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) (limited to 'sleekxmpp/xmlstream/statemachine.py') diff --git a/sleekxmpp/xmlstream/statemachine.py b/sleekxmpp/xmlstream/statemachine.py index 704cabdb..c6e0ea41 100644 --- a/sleekxmpp/xmlstream/statemachine.py +++ b/sleekxmpp/xmlstream/statemachine.py @@ -105,6 +105,32 @@ class StateMachine(object): 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." % state ) if not to_state in self.__states: -- cgit v1.2.3