deb-ceilometer/ceilometer/utils.py

# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# Copyright 2011 Justin Santa Barbara

# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""Utilities and helper functions."""

import bisect
import calendar
import copy
import datetime
import decimal
import hashlib
import multiprocessing
import struct

from oslo.utils import timeutils
from oslo.utils import units
import six


def recursive_keypairs(d, separator=':'):
    """Generator that produces sequence of keypairs for nested dictionaries."""
    for name, value in sorted(six.iteritems(d)):
        if isinstance(value, dict):
            for subname, subvalue in recursive_keypairs(value, separator):
                yield ('%s%s%s' % (name, separator, subname), subvalue)
        elif isinstance(value, (tuple, list)):
            # When doing a pair of JSON encode/decode operations to the tuple,
            # the tuple would become list. So we have to generate the value as
            # list here.

            # in the special case of the list item itself being a dict,
            # create an equivalent dict with a predictable insertion order
            # to avoid inconsistencies in the message signature computation
            # for equivalent payloads modulo ordering
            first = lambda i: i[0]
            m = map(lambda x: six.text_type(dict(sorted(x.items(), key=first))
                                            if isinstance(x, dict)
                                            else x).encode('utf-8'),
                    value)
            yield name, list(m)
        else:
            yield name, value


def restore_nesting(d, separator=':'):
    """Unwinds a flattened dict to restore nesting."""
    d = copy.copy(d) if any([separator in k for k in d.keys()]) else d
    for k, v in d.copy().items():
        if separator in k:
            top, rem = k.split(separator, 1)
            nest = d[top] if isinstance(d.get(top), dict) else {}
            nest[rem] = v
            d[top] = restore_nesting(nest, separator)
            del d[k]
    return d


def dt_to_decimal(utc):
    """Datetime to Decimal.

    Some databases don't store microseconds in datetime
    so we always store as Decimal unixtime.
    """
    if utc is None:
        return None

    decimal.getcontext().prec = 30
    return (decimal.Decimal(str(calendar.timegm(utc.utctimetuple()))) +
            (decimal.Decimal(str(utc.microsecond)) /
            decimal.Decimal("1000000.0")))


def decimal_to_dt(dec):
    """Return a datetime from Decimal unixtime format."""
    if dec is None:
        return None

    integer = int(dec)
    micro = (dec - decimal.Decimal(integer)) * decimal.Decimal(units.M)
    daittyme = datetime.datetime.utcfromtimestamp(integer)
    return daittyme.replace(microsecond=int(round(micro)))


def sanitize_timestamp(timestamp):
    """Return a naive utc datetime object."""
    if not timestamp:
        return timestamp
    if not isinstance(timestamp, datetime.datetime):
        timestamp = timeutils.parse_isotime(timestamp)
    return timeutils.normalize_time(timestamp)


def stringify_timestamps(data):
    """Stringify any datetimes in given dict."""
    isa_timestamp = lambda v: isinstance(v, datetime.datetime)
    return dict((k, v.isoformat() if isa_timestamp(v) else v)
                for (k, v) in six.iteritems(data))


def dict_to_keyval(value, key_base=None):
    """Expand a given dict to its corresponding key-value pairs.

    Generated keys are fully qualified, delimited using dot notation.
    ie. key = 'key.child_key.grandchild_key[0]'
    """
    val_iter, key_func = None, None
    if isinstance(value, dict):
        val_iter = six.iteritems(value)
        key_func = lambda k: key_base + '.' + k if key_base else k
    elif isinstance(value, (tuple, list)):
        val_iter = enumerate(value)
        key_func = lambda k: key_base + '[%d]' % k

    if val_iter:
        for k, v in val_iter:
            key_gen = key_func(k)
            if isinstance(v, dict) or isinstance(v, (tuple, list)):
                for key_gen, v in dict_to_keyval(v, key_gen):
                    yield key_gen, v
            else:
                yield key_gen, v


def lowercase_keys(mapping):
    """Converts the values of the keys in mapping to lowercase."""
    items = mapping.items()
    for key, value in items:
        del mapping[key]
        mapping[key.lower()] = value


def lowercase_values(mapping):
    """Converts the values in the mapping dict to lowercase."""
    items = mapping.items()
    for key, value in items:
        mapping[key] = value.lower()


def update_nested(original_dict, updates):
    """Updates the leaf nodes in a nest dict.

     Updates occur without replacing entire sub-dicts.
    """
    dict_to_update = copy.deepcopy(original_dict)
    for key, value in six.iteritems(updates):
        if isinstance(value, dict):
            sub_dict = update_nested(dict_to_update.get(key, {}), value)
            dict_to_update[key] = sub_dict
        else:
            dict_to_update[key] = updates[key]
    return dict_to_update


def cpu_count():
    try:
        return multiprocessing.cpu_count() or 1
    except NotImplementedError:
        return 1


def uniq(dupes, attrs):
    """Exclude elements of dupes with a duplicated set of attribute values."""
    key = lambda d: '/'.join([getattr(d, a) or '' for a in attrs])
    keys = []
    deduped = []
    for d in dupes:
        if key(d) not in keys:
            deduped.append(d)
            keys.append(key(d))
    return deduped


class HashRing(object):

    def __init__(self, nodes, replicas=100):
        self._ring = dict()
        self._sorted_keys = []

        for node in nodes:
            for r in six.moves.range(replicas):
                hashed_key = self._hash('%s-%s' % (node, r))
                self._ring[hashed_key] = node
                self._sorted_keys.append(hashed_key)
        self._sorted_keys.sort()

    @staticmethod
    def _hash(key):
        return struct.unpack_from('>I',
                                  hashlib.md5(str(key).encode()).digest())[0]

    def _get_position_on_ring(self, key):
        hashed_key = self._hash(key)
        position = bisect.bisect(self._sorted_keys, hashed_key)
        return position if position < len(self._sorted_keys) else 0

    def get_node(self, key):
        if not self._ring:
            return None
        pos = self._get_position_on_ring(key)
        return self._ring[self._sorted_keys[pos]]