Coverage for sparts/tasks/poller : 87%

# Copyright (c) 2014, Facebook, Inc.  All rights reserved. 

# 

# This source code is licensed under the BSD-style license found in the 

# LICENSE file in the root directory of this source tree. An additional grant 

# of patent rights can be found in the PATENTS file in the same directory. 

# 

from .periodic import PeriodicTask 

from threading import Event 

class PollerTask(PeriodicTask): 

    """A PeriodicTask oriented around monitoring a single value. 

    Simply override `fetch`, and the `onValueChanged()` method will be called 

    with the old and new values.  Additionally, the `getValue()` method can 

    be called by other tasks to block until the values are ready. 

    """ 

    def initTask(self): 

        self.current_value = None 

        self.fetched = Event() 

        super(PollerTask, self).initTask() 

    def execute(self, context=None): 

        new_value = self.fetch() 

        if self.current_value != new_value: 

            self.onValueChanged(self.current_value, new_value) 

        self.current_value = new_value 

        self.fetched.set() 

    def onValueChanged(self, old_value, new_value): 

        self.logger.debug('onValueChanged(%s, %s)', old_value, new_value) 

    def fetch(self): 

        self.logger.debug('fetch') 

        return None 

    def getValue(self, timeout=None): 

        self.fetched.wait(timeout) 

        return self.current_value