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distribution.py
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from .meta import MetaObject
from .revision import update_revision_information
# update version information directly from SVN
update_revision_information("$HeadURL$", "$Revision$")
"""
Each Privilege can be distributed, usualy through the transfer of a message, in different ways.
These ways are defined by DistributionMeta object that is associated to the Privilege.
The DistributionMeta associated to the Privilege is used to create a Distribution object that is
assigned to the Message.
Example: A community has a permission called 'user-name'. This Permission has the
LastSyncDistributionMeta object assigned to it. The LastSyncDistributionMeta object dictates some
values such as the size and stepping used for the BloomFilter.
Whenever a the 'user-name' Permission is used, a LastSyncDistribution object is created. The
LastSyncDistribution object holds additional information for this specific message, such as the
global_time.
"""
class Distribution(MetaObject):
class Implementation(MetaObject.Implementation):
def __init__(self, meta, global_time):
assert isinstance(meta, Distribution)
assert isinstance(global_time, (int, long))
assert global_time > 0
super(Distribution.Implementation, self).__init__(meta)
# the last known global time + 1 (from the user who signed the
# message)
self._global_time = global_time
@property
def global_time(self):
return self._global_time
def setup(self, message):
"""
Setup is called after the meta message is initially created.
"""
if __debug__:
from .message import Message
assert isinstance(message, Message)
class SyncDistribution(Distribution):
"""
Allows gossiping and synchronization of messages thoughout the community.
The PRIORITY value ranges [0:255] where the 0 is the lowest priority and 255 the highest. Any
messages that have a priority below 32 will not be synced. These messages require a mechanism
to request missing messages whenever they are needed.
The PRIORITY was introduced when we found that the dispersy-identity messages are the majority
of gossiped messages while very few are actually required. The dispersy-missing-identity
message is used to retrieve an identity whenever it is needed.
"""
class Implementation(Distribution.Implementation):
@property
def synchronization_direction(self):
return self._meta._synchronization_direction
@property
def synchronization_direction_id(self):
return self._meta._synchronization_direction_id
@property
def priority(self):
return self._meta._priority
@property
def database_id(self):
return self._meta._database_id
def __init__(self, synchronization_direction, priority):
# note: messages with a high priority value are synced before those with a low priority
# value.
# note: the priority has precedence over the global_time based ordering.
# note: the default priority should be 127, use higher or lowe values when needed.
assert isinstance(synchronization_direction, unicode)
assert synchronization_direction in (u"ASC", u"DESC")
assert isinstance(priority, int)
assert 0 <= priority <= 255
self._synchronization_direction = synchronization_direction
self._priority = priority
self._current_sequence_number = 0
# self._database_id = 0
@property
def synchronization_direction(self):
return self._synchronization_direction
@property
def synchronization_direction_value(self):
return -1 if self._synchronization_direction == u"DESC" else 1
@property
def priority(self):
return self._priority
# @property
# def database_id(self):
# return self._database_id
def setup(self, message):
"""
Setup is called after the meta message is initially created.
It is used to determine the current sequence number, based on
which messages are already in the database.
"""
if __debug__:
from .message import Message
assert isinstance(message, Message)
# use cache to avoid database queries
assert message.name in message.community.meta_message_cache
cache = message.community.meta_message_cache[message.name]
if not (cache["priority"] == self._priority and cache["direction"] == self.synchronization_direction_value):
message.community.dispersy.database.execute(u"UPDATE meta_message SET priority = ?, direction = ? WHERE id = ?",
(self._priority, self.synchronization_direction_value, message.database_id))
assert message.community.dispersy.database.changes == 1
class FullSyncDistribution(SyncDistribution):
"""
Allows gossiping and synchronization of messages thoughout the community.
Sequence numbers can be enabled or disabled per meta-message. When disabled the sequence number
is always zero. When enabled the claim_sequence_number method can be called to obtain the next
requence number in sequence.
Currently there is one situation where disabling sequence numbers is required. This is when the
message will be signed by multiple members. In this case the sequence number is claimed but may
not be used (if the other members refuse to add their signature). This causes a missing
sequence message. This in turn could be solved by creating a placeholder message, however, this
is not currently, and my never be, implemented.
"""
class Implementation(SyncDistribution.Implementation):
def __init__(self, meta, global_time, sequence_number=0):
assert isinstance(sequence_number, (int, long))
assert (meta._enable_sequence_number and sequence_number > 0) or (not meta._enable_sequence_number and sequence_number == 0), (meta._enable_sequence_number, sequence_number)
super(FullSyncDistribution.Implementation, self).__init__(meta, global_time)
self._sequence_number = sequence_number
@property
def enable_sequence_number(self):
return self._meta._enable_sequence_number
@property
def sequence_number(self):
return self._sequence_number
def __init__(self, synchronization_direction, priority, enable_sequence_number):
assert isinstance(enable_sequence_number, bool)
super(FullSyncDistribution, self).__init__(synchronization_direction, priority)
self._enable_sequence_number = enable_sequence_number
@property
def enable_sequence_number(self):
return self._enable_sequence_number
def setup(self, message):
super(FullSyncDistribution, self).setup(message)
if self._enable_sequence_number:
# obtain the most recent sequence number that we have used
self._current_sequence_number, = message.community.dispersy.database.execute(u"SELECT COUNT(1) FROM sync WHERE member = ? AND meta_message = ?",
(message.community.my_member.database_id, message.database_id)).next()
def claim_sequence_number(self):
assert self._enable_sequence_number
self._current_sequence_number += 1
return self._current_sequence_number
class LastSyncDistribution(SyncDistribution):
class Implementation(SyncDistribution.Implementation):
@property
def cluster(self):
return self._meta._cluster
@property
def history_size(self):
return self._meta._history_size
def __init__(self, synchronization_direction, priority, history_size):
assert isinstance(history_size, int)
assert history_size > 0
super(LastSyncDistribution, self).__init__(synchronization_direction, priority)
self._history_size = history_size
@property
def history_size(self):
return self._history_size
class DirectDistribution(Distribution):
class Implementation(Distribution.Implementation):
pass
class RelayDistribution(Distribution):
class Implementation(Distribution.Implementation):
pass