Source code for taurus.core.util.event

#!/usr/bin/env python

#############################################################################
##
# This file is part of Taurus
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# http://taurus-scada.org
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# Copyright 2011 CELLS / ALBA Synchrotron, Bellaterra, Spain
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# Taurus is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
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# Taurus is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
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# You should have received a copy of the GNU Lesser General Public License
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#############################################################################

"""
event.py:
"""
from __future__ import print_function
from __future__ import absolute_import
from builtins import range
from builtins import object
import sys
import weakref
import threading
import time
import collections
import taurus.core


__all__ = ["BoundMethodWeakref", "CallableRef", "EventGenerator",
           "ConfigEventGenerator", "ListEventGenerator", "EventListener",
           "AttributeEventWait", "AttributeEventIterator"]

__docformat__ = "restructuredtext"


[docs]class BoundMethodWeakref(object): """This class represents a weak reference to a method of an object since weak references to methods don't work by themselves""" def __init__(self, bound_method, del_cb=None): cb = (del_cb and self._deleted) self.func_ref = weakref.ref(bound_method.__func__, cb) self.obj_ref = weakref.ref(bound_method.__self__, cb) if cb: self.del_cb = CallableRef(del_cb) self.already_deleted = 0 def _deleted(self, obj): if not self.already_deleted: del_cb = self.del_cb() if del_cb is not None: del_cb(self) self.already_deleted = 1 def __call__(self): obj = self.obj_ref() if obj is not None: func = self.func_ref() if func is not None: return func.__get__(obj) def __hash__(self): return id(self) def __cmp__(self, other): if other.__class__ == self.__class__: from past.builtins import cmp ret = cmp((self.func_ref, self.obj_ref), (other.func_ref, other.obj_ref)) return ret return 1 def __eq__(self, other): if hasattr(other, 'func_ref') and hasattr(other, 'obj_ref'): return ((self.func_ref, self.obj_ref) == (other.func_ref, other.obj_ref)) return False def __ne__(self, other): return not self == other def __repr__(self): obj, func = self.obj_ref(), self.func_ref() return 'BoundMethodWeakRef of %s.%s' % (obj, func)
[docs]def CallableRef(object, del_cb=None): """This function returns a callable weak reference to a callable object. Object can be a callable object, a function or a method. :param object: a callable object :type object: callable object :param del_cb: calback function. Default is None meaning to callback. :type del_cb: callable object or None :return: a weak reference for the given callable :rtype: taurus.core.util.BoundMethodWeakref or weakref.ref """ im_self = None if hasattr(object, '__self__'): im_self = object.__self__ elif hasattr(object, 'im_self'): im_self = object.im_self if im_self is not None: return BoundMethodWeakref(object, del_cb) return weakref.ref(object, del_cb)
# Reimplementation of BoundMethodWeakref class to avoid to have a hard # reference in the event callbacks. # Related to "Keeping references to event callbacks after unsubscribe_event" # PyTango #185 issue. class _BoundMethodWeakrefWithCall(BoundMethodWeakref): def __init__(self, bound_method, del_cb=None): """ Reimplementation of __init__ method""" super(_BoundMethodWeakrefWithCall, self).__init__(bound_method, del_cb=del_cb) self.__name__ = self.func_ref().__name__ def __call__(self, *args, **kwargs): """ Retrieve references and call callback with arguments """ obj = self.obj_ref() if obj is not None: func = self.func_ref() if func is not None: return func(obj, *args, **kwargs) class EventStack(object): "internal usage event stack" def __init__(self, history=True): self.unread_stack = [] self.read_stack = [] self.history = history def isEmpty(self): return len(self.unread_stack) == 0 def push(self, event): self.unread_stack.append(event) def getNext(self): if self.isEmpty(): return None event = self.unread_stack[0] del self.unread_stack[0] if self.history: self.read_stack.append(event) return event def getAllUnread(self): unread = self.unread_stack self.unread_stack = [] return unread def getAllRead(self): read = self.read_stack self.read_stack = [] return read from .object import Object
[docs]class EventGenerator(Object): """Base class capable of firing events""" WaitTimeout = 0.1 def __init__(self, name, events_active=True): """Event generator constructor. :param name: the event generator name :type name: str :param events_active: generate events (default is True) :type events_active: bool :return: a new EventGenerator :rtype: EventGenerator""" self.call__init__(Object) self.event_name = name self.cb_list = [] self.last_val = None self.first_event_val = None self.events_active = events_active self.cond = threading.Condition() self.wait_list = []
[docs] def lock(self): """Locks this event generator""" self.cond.acquire()
[docs] def unlock(self): """Unlocks this event generator""" if self.cond._is_owned(): self.cond.release() else: pass
[docs] def subscribeEvent(self, cb, data=None, with_first_event=True): """Subscribes to the event :param cb: a callable object :type cb: callable :param data: extra data to send each time an event is triggered on the given callback. Default is None. :type data: object :param with_first_event: whether call the callback with the first event value (the most recent value) during the subscription process. Default is True. :type data: boolean """ if not self.events_active: raise RuntimeError('%s does not have ' 'events/polling active' % self.event_name) cb_ref = CallableRef(cb, self.unsubscribeDeletedEvent) try: self.lock() if (cb_ref, data) in self.cb_list: raise RuntimeError('Callback %s(%s) already reg. on %s' % (cb, data, self.event_name)) self.cb_list.append((cb_ref, data)) if with_first_event: cb(data, self.first_event_val) finally: self.unlock()
[docs] def unsubscribeDeletedEvent(self, cb_ref): """for internal usage only""" try: self.lock() aux_list = list(self.cb_list) for i in range(len(aux_list) - 1, -1, -1): pair = self.cb_list[i] if pair[0] is cb_ref: del self.cb_list[i] finally: self.unlock()
[docs] def unsubscribeEvent(self, cb, data=None): """Unsubscribes the given callback from the event. If the callback is not a listener for this event a debug message is generated an nothing happens. :param cb: a callable object :type cb: callable :param data: extra data to send each time an event is triggered on the given callback. Default is None :type data: object""" cb_ref = CallableRef(cb) try: self.lock() if (cb_ref, data) in self.cb_list: self.cb_list.remove((cb_ref, data)) else: self.debug("Trying to unsubscribe: %s is not a listener of %s" % ( str(cb_ref), self.event_name)) finally: self.unlock()
[docs] def isSubscribed(self, cb, data=None): """Determines if the given callback is registered for this event. :param cb: a callable object :type cb: callable :param data: extra data to send each time an event is triggered on the given callback. Default is None :type data: object :return: True if callback is registered or False otherwise :rtype: bool""" cb_ref = CallableRef(cb, self.unsubscribeDeletedEvent) return (cb_ref, data) in self.cb_list
[docs] def setEventsActive(self, events_active): """(De)activates events on this event generator. :param events_active: activate/deactivate events :type events_active: bool""" self.events_active = events_active
[docs] def getEventsActive(self): """Determines is events are active :return: True if events are active or False otherwise :rtype: bool""" return self.events_active
[docs] def fireEvent(self, val, event_val=None): """Fires an event. :param val: event value :type val: object""" try: self.lock() self.last_val = val self.cond.notifyAll() if event_val is None: event_val = val self.first_event_val = event_val for stack in self.wait_list: stack.push(event_val) for cb_ref, data in self.cb_list: cb = cb_ref() if cb is not None: cb(data, event_val) finally: self.unlock()
[docs] def waitEvent(self, val=None, equal=True, any=False, timeout=None, stack=None): """Waits for an event to occur :param val: event value :type val: object :param equal: check for equality. Default is True :type equal: bool :param any: if True unblock after first event, not matter what value it has. Default is False. :type any: bool :param timeout: maximum time to wait (seconds). Default is None meaning wait forever. :type timeout: float :param stack: For internal usage only. :return: the value of the event that unblocked the wait :rtype: object""" if not self.events_active: raise RuntimeError('%s does not have ' 'events/polling active' % self.event_name) try: self.lock() t0 = time.time() timeout_expired = False stack = stack or EventStack(history=False) while True: curr_val = self.last_val avail = not stack.isEmpty() if avail: curr_val = stack.getNext() if any: block = not avail else: block = ((equal and (val != curr_val)) or (not equal and (val == curr_val))) if timeout: timeout_expired = (time.time() - t0 > timeout) if not block or timeout_expired: break self.wait_list.append(stack) self.cond.wait(self.WaitTimeout) self.wait_list.remove(stack) val = curr_val finally: self.unlock() return val
[docs] def read(self): """Read the last event :return: the last event value :rtype: object""" return self.last_val
[docs]class EventListener(object): """A class that listens for an event with a specific value Note: Since this class stores for each event value the last timestamp when it occured, it should only be used for events for which the event value domain (possible values) is limited and well known (ex: an enum)""" def __init__(self): self.last_val = None self.cond = threading.Condition() # a set implemented as a dictionary # dict<object, float> # key - event value # value - timestamp of last event with that value self.event_set = {} self.attr.addListener(self)
[docs] def lock(self): """Locks this event listener""" self.cond.acquire()
[docs] def unlock(self): """Unlocks this event listener""" if self.cond._is_owned(): self.cond.release() else: pass
[docs] def clearEventSet(self): "Clears the internal event buffer" self.event_set.clear()
[docs] def fireEvent(self, v): """Notifies that a given event has arrived This function is protected inside with the object's lock. Do NOT call this function when you have the lock acquired on this object. :param v: event value :type v: object""" try: t = time.time() self.lock() self.last_val = v self.event_set[v] = t self.cond.notifyAll() finally: self.unlock()
[docs] def waitEvent(self, val, after=0, equal=True): """Wait for an event with the given value. You MUST protect this function with this object's lock before calling this method and always unlock it afterward, of course:: from taurus.core.util.event import EventListener class MyEvtListener(EventListener): # Your specific listener code here pass evt_listener = EventListener() try: evt_listener.lock() t = time.time() go() evt_listener.waitEvent(Stop, t) finally: evt_listener.unlock() :param val: value to compare :type val: object :param after: timestamp. wait for events comming after the given time. default value is 0 meaning any event after Jan 1, 1970 :type after: float :param equal: compare for equality. equal=True means an event with the given value, equal=False means any event which as a different value :type equal: bool """ s = self.event_set while True: if equal: t = s.get(val) if t and t >= after: return else: for v, t in list(s.items()): if v == val: continue if t >= after: return self.cond.wait()
[docs]class ConfigEventGenerator(EventGenerator): """Manage configuration events"""
[docs] def fireEvent(self, val, event_val=None): EventGenerator.fireEvent(self, val, event_val)
[docs]class ListEventGenerator(EventGenerator): """Manage list events, detecting changes in the list""" def __init__(self, name, events_active=True): self.call__init__(EventGenerator, name, events_active) self.last_val = [] self.first_event_val = [], [], []
[docs] def fireEvent(self, val): """Notifies that a given event has arrived This function is protected inside with the object's lock. Do NOT call this function when you have the lock acquired on this object. :param val: event value :type val: object""" # if attribute is not alive and last time was also not alive then # skip the event propagation if val is None: if len(self.last_val) == 0: return val = [] try: self.lock() val = list(val) last_val = self.last_val rm = [x for x in last_val if x not in val] add = [x for x in val if x not in last_val] event_val = val, rm, add EventGenerator.fireEvent(self, val, event_val) self.first_event_val = val, [], val finally: self.unlock()
[docs]class AttributeEventWait(object): """Class designed to connect to a :class:`taurus.core.taurusattribute.TaurusAttribute` and fire events or wait for a certain event.""" def __init__(self, attr=None): self._last_val = None self._attr = None self._cond = threading.Condition() self._event_set = {} if attr is not None: self.connect(attr)
[docs] def connect(self, attr): """Connect to the given attribute :param attr: the attribute to connect to :type attr: taurus.core.taurusattribute.TaurusAttribute""" needAdd = True if self._attr is not None: if attr == self._attr: needAdd = False else: self._attr.removeListener(self) self.clearEventSet() self._last_val = None self._attr = attr if needAdd: self._attr.addListener(self)
[docs] def disconnect(self): """Disconnects from the attribute. If not connected nothing happens.""" self.clearEventSet() if self._attr: self._attr.removeListener(self) self._attr = None self._last_val = None
[docs] def lock(self): """Locks this event listener""" self._cond.acquire()
[docs] def unlock(self): """Unocks this event listener""" if self._cond._is_owned(): self._cond.release() else: lock = getattr(self._cond, "_Condition__lock") th = getattr(lock, "_RLock__owner") curr_th = threading.current_thread() if th is not None: name = th.name else: name = "<unknown>" print("WARNING: Thread %s trying to unlock condition previously " \ "locked by thread %s" % (curr_th.name, name))
[docs] def clearEventSet(self): "Clears the internal event buffer" self._event_set.clear() self._last_val = None
[docs] def eventReceived(self, s, t, v): """Event listener method for the underlying attribute. Do not call this method. It will be called internally when the attribute generates an event.""" if t == taurus.core.taurusbasetypes.TaurusEventType.Config: return elif t == taurus.core.taurusbasetypes.TaurusEventType.Error: self.fireEvent(None) else: self.fireEvent(v.rvalue)
[docs] def fireEvent(self, v): """Notifies that a given event has arrived This function is protected inside with the object's lock. Do NOT call this function when you have the lock acquired on this object. :param v: event value :type v: object""" t = time.time() self.lock() try: self._last_val = v self._event_set[v] = t self._cond.notifyAll() finally: self.unlock()
[docs] def getLastRecordedEvent(self): """returns the value of the last recorded event or None if no event has been received or the last event was an error event :return: the last event value to be recorded :rtype: object""" return self._last_val
[docs] def getRecordedEvents(self): """Returns a reference to the internal dictionary used to store the internal events. Modify the return dictionary at your own risk! :return: reference to the internal event dictionary :rtype: dict""" return self._event_set
[docs] def getRecordedEvent(self, v): """Returns the the recorded local timestamp for the event with the given value or None if no event with the given value has been recorded. :param v: event value :type v: object :return: local timestamp for the event or None if no event has been recorded :rtype: float""" return self._event_set.get(v)
[docs] def waitEvent(self, val, after=0, equal=True, timeout=None, retries=-1, any=False): """Wait for an event with the given value. :param val: value to compare :type val: object :param after: timestamp. wait for events comming after the given time. default value is 0 meaning any event after Jan 1, 1970 :type after: float :param equal: compare for equality. equal=True means an event with the given value, equal=False means any event which as a different value :type equal: bool :param timeout: maximum time to wait (seconds). Default is None meaning wait forever. :type timeout: float :param retries: number of maximum retries of max timeout to attempts. Default is -1 meaning infinite number of retries. 0 means no wait. Positive number is obvious. :param any: if any is True ignore 'val' parameter and accept any event. If False (default),check with given 'val' parameter :type any: bool """ if retries == 0: return if timeout is None: # if waitting forever doesn't make sense to retry retries = 1 if after is None: after = 0 s = self._event_set self.lock() try: # increase the retries by one just because of how the loop is done if retries > 0: retries += 1 while retries != 0: if any: for v, t in s.items(): if t >= after: return if equal: t = s.get(val) if (t is not None) and (t >= after): return else: for v, t in s.items(): if v == val: continue if t >= after: return self._cond.wait(timeout) retries -= 1 except Exception as e: sys.stderr.write( "AttributeEventWait: Caught exception while waiting: %s\n" % str(e)) raise e finally: self.unlock()
[docs]class AttributeEventIterator(object): """Internal class. For test purposes""" def __init__(self, *attrs): self._attrs = None self._cond = threading.Condition() if len(attrs) > 0: self.connect(attrs)
[docs] def connect(self, attrs): if not isinstance(attrs, collections.Sequence): attrs = (attrs,) self.disconnect() self._attrs = attrs for attr in self._attrs: attr.addListener(self)
[docs] def disconnect(self): if self._attrs is None: return for attr in self._attrs: attr.removeListener(self)
[docs] def lock(self): self._cond.acquire()
[docs] def unlock(self): if self._cond._is_owned(): self._cond.release() else: lock = getattr(self._cond, "_Condition__lock") th = getattr(lock, "_RLock__owner") curr_th = threading.current_thread() print(("WARNING: Thread %s trying to unlock condition previously " + "locked by thread %s") % (curr_th.name, th.name))
[docs] def eventReceived(self, s, t, v): if t not in (taurus.core.taurusbasetypes.TaurusEventType.Change, taurus.core.taurusbasetypes.TaurusEventType.Periodic): return self.fireEvent(s, v.rvalue)
[docs] def fireEvent(self, s, v): t = time.time() self.lock() try: self._data = s, v self._cond.notifyAll() finally: self.unlock()
[docs] def events(self, timeout=1): self.lock() try: while True: self._cond.wait(timeout) yield self._data except Exception as e: print("INFO: Caught exception while waiting", str(e)) finally: self.unlock()