diff --git a/synapse/util/async.py b/synapse/util/async.py
deleted file mode 100644
index a7094e2fb4..0000000000
--- a/synapse/util/async.py
+++ /dev/null
@@ -1,415 +0,0 @@
-# -*- coding: utf-8 -*-
-# Copyright 2014-2016 OpenMarket Ltd
-# Copyright 2018 New Vector Ltd.
-#
-# 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.
-import collections
-import logging
-from contextlib import contextmanager
-
-from six.moves import range
-
-from twisted.internet import defer
-from twisted.internet.defer import CancelledError
-from twisted.python import failure
-
-from synapse.util import Clock, logcontext, unwrapFirstError
-
-from .logcontext import (
- PreserveLoggingContext,
- make_deferred_yieldable,
- run_in_background,
-)
-
-logger = logging.getLogger(__name__)
-
-
-class ObservableDeferred(object):
- """Wraps a deferred object so that we can add observer deferreds. These
- observer deferreds do not affect the callback chain of the original
- deferred.
-
- If consumeErrors is true errors will be captured from the origin deferred.
-
- Cancelling or otherwise resolving an observer will not affect the original
- ObservableDeferred.
-
- NB that it does not attempt to do anything with logcontexts; in general
- you should probably make_deferred_yieldable the deferreds
- returned by `observe`, and ensure that the original deferred runs its
- callbacks in the sentinel logcontext.
- """
-
- __slots__ = ["_deferred", "_observers", "_result"]
-
- def __init__(self, deferred, consumeErrors=False):
- object.__setattr__(self, "_deferred", deferred)
- object.__setattr__(self, "_result", None)
- object.__setattr__(self, "_observers", set())
-
- def callback(r):
- object.__setattr__(self, "_result", (True, r))
- while self._observers:
- try:
- # TODO: Handle errors here.
- self._observers.pop().callback(r)
- except Exception:
- pass
- return r
-
- def errback(f):
- object.__setattr__(self, "_result", (False, f))
- while self._observers:
- try:
- # TODO: Handle errors here.
- self._observers.pop().errback(f)
- except Exception:
- pass
-
- if consumeErrors:
- return None
- else:
- return f
-
- deferred.addCallbacks(callback, errback)
-
- def observe(self):
- """Observe the underlying deferred.
-
- Can return either a deferred if the underlying deferred is still pending
- (or has failed), or the actual value. Callers may need to use maybeDeferred.
- """
- if not self._result:
- d = defer.Deferred()
-
- def remove(r):
- self._observers.discard(d)
- return r
- d.addBoth(remove)
-
- self._observers.add(d)
- return d
- else:
- success, res = self._result
- return res if success else defer.fail(res)
-
- def observers(self):
- return self._observers
-
- def has_called(self):
- return self._result is not None
-
- def has_succeeded(self):
- return self._result is not None and self._result[0] is True
-
- def get_result(self):
- return self._result[1]
-
- def __getattr__(self, name):
- return getattr(self._deferred, name)
-
- def __setattr__(self, name, value):
- setattr(self._deferred, name, value)
-
- def __repr__(self):
- return "<ObservableDeferred object at %s, result=%r, _deferred=%r>" % (
- id(self), self._result, self._deferred,
- )
-
-
-def concurrently_execute(func, args, limit):
- """Executes the function with each argument conncurrently while limiting
- the number of concurrent executions.
-
- Args:
- func (func): Function to execute, should return a deferred.
- args (list): List of arguments to pass to func, each invocation of func
- gets a signle argument.
- limit (int): Maximum number of conccurent executions.
-
- Returns:
- deferred: Resolved when all function invocations have finished.
- """
- it = iter(args)
-
- @defer.inlineCallbacks
- def _concurrently_execute_inner():
- try:
- while True:
- yield func(next(it))
- except StopIteration:
- pass
-
- return logcontext.make_deferred_yieldable(defer.gatherResults([
- run_in_background(_concurrently_execute_inner)
- for _ in range(limit)
- ], consumeErrors=True)).addErrback(unwrapFirstError)
-
-
-class Linearizer(object):
- """Limits concurrent access to resources based on a key. Useful to ensure
- only a few things happen at a time on a given resource.
-
- Example:
-
- with (yield limiter.queue("test_key")):
- # do some work.
-
- """
- def __init__(self, name=None, max_count=1, clock=None):
- """
- Args:
- max_count(int): The maximum number of concurrent accesses
- """
- if name is None:
- self.name = id(self)
- else:
- self.name = name
-
- if not clock:
- from twisted.internet import reactor
- clock = Clock(reactor)
- self._clock = clock
- self.max_count = max_count
-
- # key_to_defer is a map from the key to a 2 element list where
- # the first element is the number of things executing, and
- # the second element is an OrderedDict, where the keys are deferreds for the
- # things blocked from executing.
- self.key_to_defer = {}
-
- @defer.inlineCallbacks
- def queue(self, key):
- entry = self.key_to_defer.setdefault(key, [0, collections.OrderedDict()])
-
- # If the number of things executing is greater than the maximum
- # then add a deferred to the list of blocked items
- # When on of the things currently executing finishes it will callback
- # this item so that it can continue executing.
- if entry[0] >= self.max_count:
- new_defer = defer.Deferred()
- entry[1][new_defer] = 1
-
- logger.info(
- "Waiting to acquire linearizer lock %r for key %r", self.name, key,
- )
- try:
- yield make_deferred_yieldable(new_defer)
- except Exception as e:
- if isinstance(e, CancelledError):
- logger.info(
- "Cancelling wait for linearizer lock %r for key %r",
- self.name, key,
- )
- else:
- logger.warn(
- "Unexpected exception waiting for linearizer lock %r for key %r",
- self.name, key,
- )
-
- # we just have to take ourselves back out of the queue.
- del entry[1][new_defer]
- raise
-
- logger.info("Acquired linearizer lock %r for key %r", self.name, key)
- entry[0] += 1
-
- # if the code holding the lock completes synchronously, then it
- # will recursively run the next claimant on the list. That can
- # relatively rapidly lead to stack exhaustion. This is essentially
- # the same problem as http://twistedmatrix.com/trac/ticket/9304.
- #
- # In order to break the cycle, we add a cheeky sleep(0) here to
- # ensure that we fall back to the reactor between each iteration.
- #
- # (This needs to happen while we hold the lock, and the context manager's exit
- # code must be synchronous, so this is the only sensible place.)
- yield self._clock.sleep(0)
-
- else:
- logger.info(
- "Acquired uncontended linearizer lock %r for key %r", self.name, key,
- )
- entry[0] += 1
-
- @contextmanager
- def _ctx_manager():
- try:
- yield
- finally:
- logger.info("Releasing linearizer lock %r for key %r", self.name, key)
-
- # We've finished executing so check if there are any things
- # blocked waiting to execute and start one of them
- entry[0] -= 1
-
- if entry[1]:
- (next_def, _) = entry[1].popitem(last=False)
-
- # we need to run the next thing in the sentinel context.
- with PreserveLoggingContext():
- next_def.callback(None)
- elif entry[0] == 0:
- # We were the last thing for this key: remove it from the
- # map.
- del self.key_to_defer[key]
-
- defer.returnValue(_ctx_manager())
-
-
-class ReadWriteLock(object):
- """A deferred style read write lock.
-
- Example:
-
- with (yield read_write_lock.read("test_key")):
- # do some work
- """
-
- # IMPLEMENTATION NOTES
- #
- # We track the most recent queued reader and writer deferreds (which get
- # resolved when they release the lock).
- #
- # Read: We know its safe to acquire a read lock when the latest writer has
- # been resolved. The new reader is appeneded to the list of latest readers.
- #
- # Write: We know its safe to acquire the write lock when both the latest
- # writers and readers have been resolved. The new writer replaces the latest
- # writer.
-
- def __init__(self):
- # Latest readers queued
- self.key_to_current_readers = {}
-
- # Latest writer queued
- self.key_to_current_writer = {}
-
- @defer.inlineCallbacks
- def read(self, key):
- new_defer = defer.Deferred()
-
- curr_readers = self.key_to_current_readers.setdefault(key, set())
- curr_writer = self.key_to_current_writer.get(key, None)
-
- curr_readers.add(new_defer)
-
- # We wait for the latest writer to finish writing. We can safely ignore
- # any existing readers... as they're readers.
- yield make_deferred_yieldable(curr_writer)
-
- @contextmanager
- def _ctx_manager():
- try:
- yield
- finally:
- new_defer.callback(None)
- self.key_to_current_readers.get(key, set()).discard(new_defer)
-
- defer.returnValue(_ctx_manager())
-
- @defer.inlineCallbacks
- def write(self, key):
- new_defer = defer.Deferred()
-
- curr_readers = self.key_to_current_readers.get(key, set())
- curr_writer = self.key_to_current_writer.get(key, None)
-
- # We wait on all latest readers and writer.
- to_wait_on = list(curr_readers)
- if curr_writer:
- to_wait_on.append(curr_writer)
-
- # We can clear the list of current readers since the new writer waits
- # for them to finish.
- curr_readers.clear()
- self.key_to_current_writer[key] = new_defer
-
- yield make_deferred_yieldable(defer.gatherResults(to_wait_on))
-
- @contextmanager
- def _ctx_manager():
- try:
- yield
- finally:
- new_defer.callback(None)
- if self.key_to_current_writer[key] == new_defer:
- self.key_to_current_writer.pop(key)
-
- defer.returnValue(_ctx_manager())
-
-
-class DeferredTimeoutError(Exception):
- """
- This error is raised by default when a L{Deferred} times out.
- """
-
-
-def add_timeout_to_deferred(deferred, timeout, reactor, on_timeout_cancel=None):
- """
- Add a timeout to a deferred by scheduling it to be cancelled after
- timeout seconds.
-
- This is essentially a backport of deferred.addTimeout, which was introduced
- in twisted 16.5.
-
- If the deferred gets timed out, it errbacks with a DeferredTimeoutError,
- unless a cancelable function was passed to its initialization or unless
- a different on_timeout_cancel callable is provided.
-
- Args:
- deferred (defer.Deferred): deferred to be timed out
- timeout (Number): seconds to time out after
- reactor (twisted.internet.reactor): the Twisted reactor to use
-
- on_timeout_cancel (callable): A callable which is called immediately
- after the deferred times out, and not if this deferred is
- otherwise cancelled before the timeout.
-
- It takes an arbitrary value, which is the value of the deferred at
- that exact point in time (probably a CancelledError Failure), and
- the timeout.
-
- The default callable (if none is provided) will translate a
- CancelledError Failure into a DeferredTimeoutError.
- """
- timed_out = [False]
-
- def time_it_out():
- timed_out[0] = True
- deferred.cancel()
-
- delayed_call = reactor.callLater(timeout, time_it_out)
-
- def convert_cancelled(value):
- if timed_out[0]:
- to_call = on_timeout_cancel or _cancelled_to_timed_out_error
- return to_call(value, timeout)
- return value
-
- deferred.addBoth(convert_cancelled)
-
- def cancel_timeout(result):
- # stop the pending call to cancel the deferred if it's been fired
- if delayed_call.active():
- delayed_call.cancel()
- return result
-
- deferred.addBoth(cancel_timeout)
-
-
-def _cancelled_to_timed_out_error(value, timeout):
- if isinstance(value, failure.Failure):
- value.trap(CancelledError)
- raise DeferredTimeoutError(timeout, "Deferred")
- return value
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