270 lines
9.6 KiB
Python
270 lines
9.6 KiB
Python
# Copyright (c) 2010-2012 OpenStack, LLC.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import array
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import cPickle as pickle
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from collections import defaultdict
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from gzip import GzipFile
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from os.path import getmtime
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import struct
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from time import time
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import os
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from io import BufferedReader
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from swift.common.utils import hash_path, validate_configuration
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from swift.common.ring.utils import tiers_for_dev
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try:
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import simplejson as json
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except ImportError:
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import json
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class RingData(object):
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"""Partitioned consistent hashing ring data (used for serialization)."""
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def __init__(self, replica2part2dev_id, devs, part_shift):
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self.devs = devs
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self._replica2part2dev_id = replica2part2dev_id
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self._part_shift = part_shift
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@classmethod
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def deserialize_v1(cls, gz_file):
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json_len, = struct.unpack('!I', gz_file.read(4))
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ring_dict = json.loads(gz_file.read(json_len))
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ring_dict['replica2part2dev_id'] = []
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partition_count = 1 << (32 - ring_dict['part_shift'])
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for x in xrange(ring_dict['replica_count']):
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ring_dict['replica2part2dev_id'].append(
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array.array('H', gz_file.read(2 * partition_count)))
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return ring_dict
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@classmethod
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def load(cls, filename):
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"""
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Load ring data from a file.
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:param filename: Path to a file serialized by the save() method.
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:returns: A RingData instance containing the loaded data.
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"""
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gz_file = GzipFile(filename, 'rb')
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# Python 2.6 GzipFile doesn't support BufferedIO
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if hasattr(gz_file, '_checkReadable'):
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gz_file = BufferedReader(gz_file)
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# See if the file is in the new format
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magic = gz_file.read(4)
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if magic == 'R1NG':
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version, = struct.unpack('!H', gz_file.read(2))
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if version == 1:
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ring_data = cls.deserialize_v1(gz_file)
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else:
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raise Exception('Unknown ring format version %d' % version)
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else:
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# Assume old-style pickled ring
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gz_file.seek(0)
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ring_data = pickle.load(gz_file)
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if not hasattr(ring_data, 'devs'):
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ring_data = RingData(ring_data['replica2part2dev_id'],
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ring_data['devs'], ring_data['part_shift'])
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return ring_data
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def serialize_v1(self, file_obj):
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# Write out new-style serialization magic and version:
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file_obj.write(struct.pack('!4sH', 'R1NG', 1))
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ring = self.to_dict()
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json_text = json.dumps(
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{'devs': ring['devs'], 'part_shift': ring['part_shift'],
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'replica_count': len(ring['replica2part2dev_id'])})
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json_len = len(json_text)
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file_obj.write(struct.pack('!I', json_len))
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file_obj.write(json_text)
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for part2dev_id in ring['replica2part2dev_id']:
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file_obj.write(part2dev_id.tostring())
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def save(self, filename):
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"""
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Serialize this RingData instance to disk.
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:param filename: File into which this instance should be serialized.
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"""
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gz_file = GzipFile(filename, 'wb')
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self.serialize_v1(gz_file)
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gz_file.close()
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def to_dict(self):
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return {'devs': self.devs,
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'replica2part2dev_id': self._replica2part2dev_id,
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'part_shift': self._part_shift}
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class Ring(object):
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"""
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Partitioned consistent hashing ring.
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:param serialized_path: path to serialized RingData instance
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:param reload_time: time interval in seconds to check for a ring change
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"""
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def __init__(self, serialized_path, reload_time=15, ring_name=None):
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# can't use the ring unless HASH_PATH_SUFFIX is set
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validate_configuration()
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if ring_name:
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self.serialized_path = os.path.join(serialized_path,
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ring_name + '.ring.gz')
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else:
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self.serialized_path = os.path.join(serialized_path)
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self.reload_time = reload_time
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self._reload(force=True)
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def _reload(self, force=False):
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self._rtime = time() + self.reload_time
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if force or self.has_changed():
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ring_data = RingData.load(self.serialized_path)
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self._mtime = getmtime(self.serialized_path)
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self._devs = ring_data.devs
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self._replica2part2dev_id = ring_data._replica2part2dev_id
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self._part_shift = ring_data._part_shift
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self._rebuild_tier_data()
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def _rebuild_tier_data(self):
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self.tier2devs = defaultdict(list)
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for dev in self._devs:
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if not dev:
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continue
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for tier in tiers_for_dev(dev):
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self.tier2devs[tier].append(dev)
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tiers_by_length = defaultdict(list)
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for tier in self.tier2devs.keys():
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tiers_by_length[len(tier)].append(tier)
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self.tiers_by_length = sorted(tiers_by_length.values(),
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key=lambda x: len(x[0]))
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for tiers in self.tiers_by_length:
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tiers.sort()
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@property
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def replica_count(self):
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"""Number of replicas used in the ring."""
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return len(self._replica2part2dev_id)
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@property
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def partition_count(self):
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"""Number of partitions in the ring."""
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return len(self._replica2part2dev_id[0])
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@property
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def devs(self):
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"""devices in the ring"""
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if time() > self._rtime:
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self._reload()
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return self._devs
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def has_changed(self):
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"""
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Check to see if the ring on disk is different than the current one in
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memory.
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:returns: True if the ring on disk has changed, False otherwise
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"""
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return getmtime(self.serialized_path) != self._mtime
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def _get_part_nodes(self, part):
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seen_ids = set()
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return [self._devs[r[part]] for r in self._replica2part2dev_id
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if not (r[part] in seen_ids or seen_ids.add(r[part]))]
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def get_part_nodes(self, part):
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"""
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Get the nodes that are responsible for the partition. If one
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node is responsible for more than one replica of the same
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partition, it will only appear in the output once.
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:param part: partition to get nodes for
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:returns: list of node dicts
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See :func:`get_nodes` for a description of the node dicts.
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"""
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if time() > self._rtime:
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self._reload()
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return self._get_part_nodes(part)
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def get_nodes(self, account, container=None, obj=None):
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"""
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Get the partition and nodes for an account/container/object.
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If a node is responsible for more than one replica, it will
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only appear in the output once.
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:param account: account name
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:param container: container name
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:param obj: object name
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:returns: a tuple of (partition, list of node dicts)
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Each node dict will have at least the following keys:
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====== ===============================================================
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id unique integer identifier amongst devices
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weight a float of the relative weight of this device as compared to
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others; this indicates how many partitions the builder will try
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to assign to this device
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zone integer indicating which zone the device is in; a given
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partition will not be assigned to multiple devices within the
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same zone
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ip the ip address of the device
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port the tcp port of the device
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device the device's name on disk (sdb1, for example)
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meta general use 'extra' field; for example: the online date, the
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hardware description
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====== ===============================================================
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"""
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key = hash_path(account, container, obj, raw_digest=True)
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if time() > self._rtime:
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self._reload()
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part = struct.unpack_from('>I', key)[0] >> self._part_shift
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return part, self._get_part_nodes(part)
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def get_more_nodes(self, part):
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"""
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Generator to get extra nodes for a partition for hinted handoff.
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:param part: partition to get handoff nodes for
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:returns: generator of node dicts
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See :func:`get_nodes` for a description of the node dicts.
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"""
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if time() > self._rtime:
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self._reload()
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used_tiers = set()
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for part2dev_id in self._replica2part2dev_id:
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for tier in tiers_for_dev(self._devs[part2dev_id[part]]):
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used_tiers.add(tier)
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for level in self.tiers_by_length:
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tiers = list(level)
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while tiers:
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tier = tiers.pop(part % len(tiers))
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if tier in used_tiers:
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continue
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for i in xrange(len(self.tier2devs[tier])):
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dev = self.tier2devs[tier][(part + i) %
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len(self.tier2devs[tier])]
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if not dev.get('weight'):
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continue
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yield dev
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used_tiers.update(tiers_for_dev(dev))
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break
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