401 lines
15 KiB
Python
401 lines
15 KiB
Python
#
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# __init__.py
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#
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# This source file is part of the FoundationDB open source project
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#
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# Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
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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 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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#
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# FoundationDB TaskBucket layer
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import random, uuid, time, struct
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import fdb, fdb.tuple
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fdb.api_version(200)
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# TODO: Make this fdb.tuple.subspace() or similar?
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class Subspace (object):
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def __init__(self, prefixTuple, rawPrefix=""):
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self.rawPrefix = rawPrefix + fdb.tuple.pack(prefixTuple)
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def __getitem__(self, name):
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return Subspace( (name,), self.rawPrefix )
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def key(self):
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return self.rawPrefix
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def pack(self, tuple):
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return self.rawPrefix + fdb.tuple.pack( tuple )
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def unpack(self, key):
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assert key.startswith(self.rawPrefix)
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return fdb.tuple.unpack(key[len(self.rawPrefix):])
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def range(self, tuple=()):
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p = fdb.tuple.range( tuple )
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return slice(self.rawPrefix + p.start, self.rawPrefix + p.stop)
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def random_key():
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return uuid.uuid4().bytes
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def _pack_value(v):
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if hasattr(v, 'pack'):
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return v.pack()
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else:
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return v
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class TaskTimedOutException(Exception):
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pass
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class TaskBucket (object):
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"""A TaskBucket represents an unordered collection of tasks, stored
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in a database and available to any number of clients. A program may
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use one or many TaskBuckets. TaskBucket represents a task as a
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key/value dictionary. See TaskDispatcher for an easy way to define
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tasks as functions."""
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def __init__(self, subspace, system_access = False):
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self.prefix = subspace
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self.active = self.prefix["ac"]
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self.available = self.prefix["av"]
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self.timeouts = self.prefix["to"]
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self.timeout = 30000
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self.system_access = system_access
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@fdb.transactional
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def clear(self, tr):
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"""Removes all tasks, whether or not locked, from the bucket."""
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if self.system_access:
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tr.options.set_access_system_keys()
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del tr[ self.prefix.range(()) ]
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@fdb.transactional
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def add(self, tr, taskDict):
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"""Adds the task specified by taskDict to the bucket for any participant to do."""
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if self.system_access:
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tr.options.set_access_system_keys()
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assert taskDict
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key = random_key()
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for k,v in taskDict.items():
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tr[ self.available.pack( (key, k) ) ] = _pack_value( v )
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taskDict["__task_key"] = key
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return key
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@fdb.transactional
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def addIdle(self, tr):
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"""Adds an idle task for any participant to remove."""
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if self.system_access:
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tr.options.set_access_system_keys()
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key = random_key()
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tr[ self.available.pack( (key, "type") ) ] = ""
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return key
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@fdb.transactional
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def get_one(self, tr):
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"""Gets a single task from the bucket, locks it so that only the
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caller will work on it for a while, and returns its taskDict.
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If there are no tasks in the bucket, returns None."""
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if self.system_access:
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tr.options.set_access_system_keys()
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k = tr.snapshot.get_key( fdb.KeySelector.last_less_or_equal( self.available.pack( (random_key(),) ) ) )
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if not k or k < self.available.pack( ("",) ):
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k = tr.snapshot.get_key( fdb.KeySelector.last_less_or_equal( self.available.pack( (chr(255)*16,) ) ) )
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if not k or k < self.available.pack( ("",) ):
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if self.check_timeouts(tr):
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return self.get_one(tr)
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return None
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key = self.available.unpack(k)[0]
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avail = self.available[key]
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timeout = tr.get_read_version().wait() + long( self.timeout * (0.9 + 0.2*random.random()) )
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taskDict = {}
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for k,v in tr[ avail.range(()) ]:
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tk, = avail.unpack(k)
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taskDict[tk]=v
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if tk != "type" or v != "":
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tr[ self.timeouts.pack( (timeout, key, tk) ) ] = v
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del tr[ avail.range(()) ]
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tr[self.active.key()] = random_key()
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taskDict["__task_key"] = key
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taskDict["__task_timeout"] = timeout
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return taskDict
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@fdb.transactional
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def is_empty(self, tr):
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if self.system_access:
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tr.options.set_read_system_keys()
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k = tr.get_key( fdb.KeySelector.last_less_or_equal( self.available.pack( (chr(255)*16,) ) ) )
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if k and k >= self.available.pack( ("",) ):
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return False
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return not bool(next(iter(tr[self.timeouts.range()]),False))
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@fdb.transactional
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def is_busy(self, tr):
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if self.system_access:
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tr.options.set_read_system_keys()
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k = tr.get_key( fdb.KeySelector.last_less_or_equal( self.available.pack( (chr(255)*16,) ) ) )
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return k and k >= self.available.pack( ("",) )
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@fdb.transactional
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def finish(self, tr, taskDict):
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"""taskDict is a task previously locked by get_one. Removes it permanently
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from the bucket. If the task has already timed out, raises TaskTimedOutException."""
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if self.system_access:
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tr.options.set_access_system_keys()
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rng = self.timeouts.range( (taskDict["__task_timeout"], taskDict["__task_key"]) )
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if next(iter(tr[rng]),False):
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del tr[ rng ]
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else:
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raise TaskTimedOutException()
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@fdb.transactional
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def is_finished(self, tr, taskDict):
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#print "checking if the task was finished at version: {0}".format(tr.get_read_version().wait())
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if self.system_access:
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tr.options.set_read_system_keys()
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rng = self.timeouts.range( (taskDict["__task_timeout"], taskDict["__task_key"]) )
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return not bool(next(iter(tr[rng]),False))
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def check_active(self, db):
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@fdb.transactional
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def get_starting_value(tr):
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if self.system_access:
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tr.options.set_read_system_keys()
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if not self.is_busy(tr):
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self.addIdle(tr)
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return tr[self.active.key()]
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starting_value = get_starting_value(db)
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@fdb.transactional
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def get_active_key(tr):
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if self.system_access:
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tr.options.set_read_system_keys()
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if tr[self.active.key()] != starting_value:
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return True
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return False
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for i in range(10):
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time.sleep(0.5)
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if get_active_key(db):
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return True
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return False
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@fdb.transactional
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def extend(self, tr, taskDict):
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"""Extends the lock on a task previously locked by get_one for another self.timeout seconds.
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If the task has already timed out, raises TaskTimedOutException."""
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pass
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def check_timeouts(self, tr):
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"""Looks for tasks that have timed out and returns them to be available tasks. Returns True
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iff any tasks were affected."""
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end = tr.get_read_version().wait()
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rng = slice( self.timeouts.range((0,)).start , self.timeouts.range((end,)).stop )
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anyTimeouts = False
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for k,v in tr.get_range( rng.start, rng.stop, streaming_mode = fdb.StreamingMode.want_all):
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timeout, taskKey, param = self.timeouts.unpack(k)
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anyTimeouts = True
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tr.set( self.available.pack( (taskKey,param) ), v )
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del tr[rng]
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return anyTimeouts
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class TaskDispatcher (object):
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def __init__(self):
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self.taskTypes = {}
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def taskType(self, f):
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"""Given a function, defines a task type with the same name as the
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function that calls the function. The function should accept the
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task dictionary as keyword parameters.
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May be used as a decorator."""
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self.taskTypes[f.__name__] = f
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return f
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def makeTask(self, f, **kw):
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"""Return a taskDict suitable for TaskBucket.add() based on a function
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which has already been passed to self.taskType() and keyword parameters
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for it."""
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assert self.taskTypes.get(f.__name__) == f
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assert 'type' not in kw
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d = dict(kw)
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d["type"] = f.__name__
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return d
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def dispatch(self, taskDict):
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"""Calls the function associated with the type of the taskDict passed
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in, passing the taskDict as keyword arguments. Does not finish or
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extend the task or otherwise interact with a TaskBucket."""
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if taskDict["type"] != "":
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self.taskTypes[ taskDict["type"] ]( **taskDict )
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def do_one(self, db, taskBucket):
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"""Gets one task (if any) from the task bucket, executes it, and finishes it.
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Returns True if a task was executed, False if none was available."""
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task = taskBucket.get_one(db)
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if not task: return False
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self.dispatch(task)
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return True
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class FutureBucket (object):
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"""A factory for Futures, and a location in the database to store them."""
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def __init__(self, subspace, system_access = False):
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self.prefix = subspace
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self.dispatcher = TaskDispatcher()
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self.dispatcher.taskType( self._add_task )
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self.dispatcher.taskType( self._unblock_future )
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self.system_access = system_access
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@fdb.transactional
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def future(self, tr):
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"""Returns a new Future which is unset."""
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if self.system_access:
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tr.options.set_access_system_keys()
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f = Future(self)
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f._add_block(tr, "")
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return f
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def unpack(self, packed_future):
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"""Returns a Future such that Future.pack()==packed_future."""
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return Future( self, packed_future )
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@fdb.transactional
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def join(self, tr, *futures):
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"""Returns a Future which is set when all of the given futures are set."""
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if self.system_access:
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tr.options.set_access_system_keys()
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joined = Future(self)
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joined._join(tr, futures)
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return joined
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def _add_task(self, tr, taskType, taskBucket, **task):
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bucket = TaskBucket( Subspace((), rawPrefix=taskBucket), system_access=self.system_access )
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task["type"] = taskType
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bucket.add( tr, task )
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def _unblock_future(self, tr, future, blockid, **task):
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if self.system_access:
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tr.options.set_access_system_keys()
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future = self.unpack(future)
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del tr[ future.prefix["bl"][blockid].key() ]
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if future.is_set(tr):
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future.perform_all_actions(tr)
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class Future (object):
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"""Represents a state which will become true ("set") at some point, and a set
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of actions to perform as soon as the state is true. The state can change
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only once."""
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def __init__(self, bucket, key=None):
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"""Not for direct use. Call FutureBucket.future() instead."""
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if key is None: key = random_key()
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self.key = key
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self.bucket = bucket
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self.prefix = bucket.prefix[ self.key ]
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self.dispatcher = bucket.dispatcher
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self.system_access = bucket.system_access
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def pack(self):
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return self.key
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@fdb.transactional
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def is_set(self, tr):
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if self.system_access:
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tr.options.set_read_system_keys()
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return not any( tr[self.prefix["bl"].range(())] )
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@fdb.transactional
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def on_set_add_task(self, tr, taskBucket, taskDict):
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"""When the Future is set, the given task will be added to the given taskBucket."""
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td = dict(taskDict)
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td["taskBucket"] = taskBucket.prefix.key()
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td["taskType"] = td["type"]
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td["type"] = "_add_task"
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self.on_set(tr, td)
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@fdb.transactional
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def on_set(self, tr, taskDict):
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"""When the Future is set, the given task will be executed immediately
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as part of the same transaction. Consider using onSetAddTask to defer
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the execution of the task instead."""
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if self.system_access:
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tr.options.set_access_system_keys()
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if self.is_set(tr):
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self.perform_action(tr, taskDict)
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else:
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cb_key = random_key()
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for k,v in taskDict.items():
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tr[ self.prefix["cb"][ cb_key ][k].key() ] = _pack_value( v )
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@fdb.transactional
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def set(self, tr):
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"""Sets the Future immediately if it has not already been set. Any
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actions that are to take place when it is set take place."""
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if self.system_access:
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tr.options.set_access_system_keys()
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#if self.is_set(tr): return
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del tr[ self.prefix.range( ("bl",) ) ] # Remove all blocks
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self.perform_all_actions(tr)
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@fdb.transactional
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def join(self, tr, *futures):
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"""This Future will be set when all of the given futures have been set.
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If this is called more than once on a Future, it is cumulative - the
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Future will be set when all of the Futures passed to any .join() are set."""
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if self.system_access:
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tr.options.set_access_system_keys()
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assert futures
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if self.is_set(tr): return
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del tr[ self.prefix["bl"][""].key() ]
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self._join(tr, futures)
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@fdb.transactional
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def joined_future(self, tr):
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"""Returns a new unset future which this future is join()ed to."""
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if self.system_access:
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tr.options.set_access_system_keys()
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f = self.bucket.future(tr)
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self.join(tr, f)
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return f
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def _join(self, tr, futures):
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ids = [random_key() for f in futures]
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for blockid in ids:
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self._add_block(tr, blockid)
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for f,blockid in zip(futures,ids):
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f.on_set( tr, self.dispatcher.makeTask( self.bucket._unblock_future, future=self.pack(), blockid=blockid ) )
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def _add_block(self, tr, blockid):
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tr[ self.prefix["bl"][blockid].key() ] = ""
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def perform_all_actions(self, tr):
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cb = self.prefix["cb"]
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callbacks = list(tr[cb.range()])
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del tr[cb.range()] # Remove all callbacks
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# Now actually perform the callbacks
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taskDict = {}
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taskKey = None
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for k,v in callbacks:
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cb_key, k = cb.unpack(k)
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if cb_key != taskKey:
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self.perform_action( tr, taskDict )
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taskDict = {}
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taskKey = cb_key
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taskDict[k] = v
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self.perform_action(tr, taskDict)
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def perform_action(self, tr, taskDict):
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if taskDict:
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taskDict["tr"] = tr
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self.dispatcher.dispatch( taskDict )
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