diff options
Diffstat (limited to 'synapse/util/async.py')
| -rw-r--r-- | synapse/util/async.py | 186 |
1 files changed, 69 insertions, 117 deletions
diff --git a/synapse/util/async.py b/synapse/util/async.py index 9dd4e6b5bc..a7094e2fb4 100644 --- a/synapse/util/async.py +++ b/synapse/util/async.py @@ -1,5 +1,6 @@ # -*- 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. @@ -12,42 +13,27 @@ # 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, reactor +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 + PreserveLoggingContext, + make_deferred_yieldable, + run_in_background, ) -from synapse.util import logcontext, unwrapFirstError - -from contextlib import contextmanager - -import logging - -from six.moves import range logger = logging.getLogger(__name__) -@defer.inlineCallbacks -def sleep(seconds): - d = defer.Deferred() - with PreserveLoggingContext(): - reactor.callLater(seconds, d.callback, seconds) - res = yield d - defer.returnValue(res) - - -def run_on_reactor(): - """ This will cause the rest of the function to be invoked upon the next - iteration of the main loop - """ - return sleep(0) - - 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 @@ -171,49 +157,72 @@ def concurrently_execute(func, args, limit): class Linearizer(object): - """Linearizes access to resources based on a key. Useful to ensure only one - thing is happening at a time on a given resource. + """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 linearizer.queue("test_key")): + with (yield limiter.queue("test_key")): # do some work. """ - def __init__(self, name=None): + 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): - # If there is already a deferred in the queue, we pull it out so that - # we can wait on it later. - # Then we replace it with a deferred that we resolve *after* the - # context manager has exited. - # We only return the context manager after the previous deferred has - # resolved. - # This all has the net effect of creating a chain of deferreds that - # wait for the previous deferred before starting their work. - current_defer = self.key_to_defer.get(key) + entry = self.key_to_defer.setdefault(key, [0, collections.OrderedDict()]) - new_defer = defer.Deferred() - self.key_to_defer[key] = new_defer + # 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 - if current_defer: logger.info( - "Waiting to acquire linearizer lock %r for key %r", self.name, key + "Waiting to acquire linearizer lock %r for key %r", self.name, key, ) try: - with PreserveLoggingContext(): - yield current_defer - except Exception: - logger.exception("Unexpected exception in Linearizer") - - logger.info("Acquired linearizer lock %r for key %r", self.name, - key) + 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 @@ -223,15 +232,15 @@ class Linearizer(object): # 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. # - # (There's no particular need for it to happen before we return - # the context manager, but it needs to happen while we hold the - # lock, and the context manager's exit code must be synchronous, - # so actually this is the only sensible place. - yield run_on_reactor() + # (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) + logger.info( + "Acquired uncontended linearizer lock %r for key %r", self.name, key, + ) + entry[0] += 1 @contextmanager def _ctx_manager(): @@ -239,73 +248,15 @@ class Linearizer(object): yield finally: logger.info("Releasing linearizer lock %r for key %r", self.name, key) - with PreserveLoggingContext(): - new_defer.callback(None) - current_d = self.key_to_defer.get(key) - if current_d is new_defer: - self.key_to_defer.pop(key, None) - - defer.returnValue(_ctx_manager()) - - -class Limiter(object): - """Limits concurrent access to resources based on a key. Useful to ensure - only a few thing happen at a time on a given resource. - - Example: - - with (yield limiter.queue("test_key")): - # do some work. - - """ - def __init__(self, max_count): - """ - Args: - max_count(int): The maximum number of concurrent access - """ - 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 - # the second element is a list of 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, []]) - - # 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].append(new_defer) - - logger.info("Waiting to acquire limiter lock for key %r", key) - with PreserveLoggingContext(): - yield new_defer - logger.info("Acquired limiter lock for key %r", key) - else: - logger.info("Acquired uncontended limiter lock for key %r", key) - - entry[0] += 1 - - @contextmanager - def _ctx_manager(): - try: - yield - finally: - logger.info("Releasing limiter lock for key %r", 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].pop(0) + (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: @@ -404,7 +355,7 @@ class DeferredTimeoutError(Exception): """ -def add_timeout_to_deferred(deferred, timeout, on_timeout_cancel=None): +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. @@ -419,6 +370,7 @@ def add_timeout_to_deferred(deferred, timeout, on_timeout_cancel=None): 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 |