make version of ts_mon compatible with appengine

infra_libs/ts_mon/distribution.py

-# Copyright 2015 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-import bisect
-import collections
-
-
-class Bucketer(object):
-  """Bucketing function for histograms recorded by the Distribution class."""
-
-  def __init__(self, width, growth_factor, num_finite_buckets):
-    """The bucket sizes are controlled by width and growth_factor, and the total
-    number of buckets is set by num_finite_buckets:
-
-    Args:
-      width: fixed size of each bucket.
-      growth_factor: if non-zero, the size of each bucket increases by another
-          multiplicative factor of this factor (see lower bound formula below).
-      num_finite_buckets: the number of finite buckets.  There are two
-          additional buckets - an underflow and an overflow bucket - that have
-          lower and upper bounds of Infinity.
-
-    Specify a width for fixed-size buckets or specify a growth_factor for bucket
-    sizes that follow a geometric progression.  Specifying both is valid as
-    well::
-
-      lower bound of bucket i = width * i + growth_factor ^ (i - 1)
-    """
-
-    if num_finite_buckets < 0:
-      raise ValueError('num_finite_buckets must be >= 0 (was %d)' %
-          num_finite_buckets)
-
-    self.width = width
-    self.growth_factor = growth_factor
-    self.num_finite_buckets = num_finite_buckets
-    self.total_buckets = num_finite_buckets + 2
-    self.underflow_bucket = 0
-    self.overflow_bucket = self.total_buckets - 1
-
-    self._lower_bounds = list(self._generate_lower_bounds())
-
-  def _generate_lower_bounds(self):
-    yield float('-Inf')
-    yield 0
-
-    previous = 0
-    for i in xrange(self.num_finite_buckets):
-      lower_bound = self.width * (i + 1)
-      if self.growth_factor != 0:
-        lower_bound += self.growth_factor ** i
-
-      if lower_bound <= previous:
-        raise ValueError('bucket boundaries must be monotonically increasing')
-      yield lower_bound
-      previous = lower_bound
-
-  def bucket_for_value(self, value):
-    """Returns the index of the bucket that this value belongs to."""
-
-    # bisect.bisect_left is wrong because the buckets are of [lower, upper) form
-    return bisect.bisect(self._lower_bounds, value) - 1
-
-  def bucket_boundaries(self, bucket):
-    """Returns a tuple that is the [lower, upper) bounds of this bucket.
-
-    The lower bound of the first bucket is -Infinity, and the upper bound of the
-    last bucket is +Infinity.
-    """
-
-    if bucket < 0 or bucket >= self.total_buckets:
-      raise IndexError('bucket %d out of range' % bucket)
-    if bucket == self.total_buckets - 1:
-      return (self._lower_bounds[bucket], float('Inf'))
-    return (self._lower_bounds[bucket], self._lower_bounds[bucket + 1])
-
-  def all_bucket_boundaries(self):
-    """Generator that produces the [lower, upper) bounds of all buckets.
-
-    This is equivalent to calling::
-
-      (b.bucket_boundaries(i) for i in xrange(b.total_buckets))
-
-    but is more efficient.
-    """
-
-    lower = self._lower_bounds[0]
-    for i in xrange(1, self.total_buckets):
-      upper = self._lower_bounds[i]
-      yield (lower, upper)
-      lower = upper
-
-    yield (lower, float('Inf'))
-
-
-def FixedWidthBucketer(width, num_finite_buckets=100):
-  """Convenience function that returns a fixed width Bucketer."""
-  return Bucketer(width=width, growth_factor=0.0,
-      num_finite_buckets=num_finite_buckets)
-
-
-def GeometricBucketer(growth_factor=10**0.2, num_finite_buckets=100):
-  """Convenience function that returns a geometric progression Bucketer."""
-  return Bucketer(width=0, growth_factor=growth_factor,
-      num_finite_buckets=num_finite_buckets)
-
-
-class Distribution(object):
-  """Holds a histogram distribution.
-
-  Buckets are chosen for values by the provided Bucketer.
-  """
-
-  def __init__(self, bucketer):
-    self.bucketer = bucketer
-    self.sum = 0
-    self.count = 0
-    self.buckets = collections.defaultdict(int)
-
-  def add(self, value):
-    self.buckets[self.bucketer.bucket_for_value(value)] += 1
-    self.sum += value
-    self.count += 1