Source code for Bcfg2.Statistics

""" Module for tracking execution time statistics from the Bcfg2
server core.  This data is exposed by
:func:`Bcfg2.Server.Core.BaseCore.get_statistics`."""


class Statistic(object):
    """ A single named statistic, tracking minimum, maximum, and
    average execution time, and number of invocations. """

    def __init__(self, name, initial_value):
        """
        :param name: The name of this statistic
        :type name: string
        :param initial_value: The initial value to be added to this
                              statistic
        :type initial_value: int or float
        """
        self.name = name
        self.min = float(initial_value)
        self.max = float(initial_value)
        self.ave = float(initial_value)
        self.count = 1

    def add_value(self, value):
        """ Add a value to the statistic, recalculating the various
        metrics.

        :param value: The value to add to this statistic
        :type value: int or float
        """
        self.min = min(self.min, float(value))
        self.max = max(self.max, float(value))
        self.count += 1
        self.ave = (((self.ave * (self.count - 1)) + value) / self.count)

    def get_value(self):
        """ Get a tuple of all the stats tracked on this named item.
        The tuple is in the format::

            (<name>, (min, max, average, number of values))

        This makes it very easy to cast to a dict in
        :func:`Statistics.display`.

        :returns: tuple
        """
        return (self.name, (self.min, self.max, self.ave, self.count))

    def __repr__(self):
        return "%s(%s, (min=%s, avg=%s, max=%s, count=%s))" % (
            self.__class__.__name__,
            self.name, self.min, self.ave, self.max, self.count)


class Statistics(object):
    """ A collection of named :class:`Statistic` objects. """

    def __init__(self):
        self.data = dict()

    def add_value(self, name, value):
        """ Add a value to the named :class:`Statistic`.  This just
        proxies to :func:`Statistic.add_value` or the
        :class:`Statistic` constructor as appropriate.

        :param name: The name of the :class:`Statistic` to add the
                     value to
        :type name: string
        :param value: The value to add to the Statistic
        :type value: int or float
        """
        if name not in self.data:
            self.data[name] = Statistic(name, value)
        else:
            self.data[name].add_value(value)

    def display(self):
        """ Return a dict of all :class:`Statistic` object values.
        Keys are the statistic names, and values are tuples of the
        statistic metrics as returned by
        :func:`Statistic.get_value`. """
        return dict([value.get_value() for value in list(self.data.values())])


#: A module-level :class:`Statistics` objects used to track all
#: execution time metrics for the server.
stats = Statistics()  # pylint: disable=C0103