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https://mau.dev/maunium/synapse.git
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231 lines
8 KiB
Python
231 lines
8 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2015 OpenMarket Ltd
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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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This module controls the reliability for application service transactions.
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The nominal flow through this module looks like:
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_________
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---ASa[e]-->| Event |
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----ASb[e]->| Grouper |<-poll 1/s--+
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--ASa[e]--->|_________| | ASa[e,e] ASb[e]
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V
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-````````- +------------+
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|````````|<--StoreTxn-|Transaction |
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|Database| | Controller |---> SEND TO AS
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`--------` +------------+
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What happens on SEND TO AS depends on the state of the Application Service:
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- If the AS is marked as DOWN, do nothing.
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- If the AS is marked as UP, send the transaction.
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* SUCCESS : Increment where the AS is up to txn-wise and nuke the txn
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contents from the db.
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* FAILURE : Marked AS as DOWN and start Recoverer.
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Recoverer attempts to recover ASes who have died. The flow for this looks like:
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,--------------------- backoff++ --------------.
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V |
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START ---> Wait exp ------> Get oldest txn ID from ----> FAILURE
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backoff DB and try to send it
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^ |___________
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Mark AS as | V
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UP & quit +---------- YES SUCCESS
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| | |
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NO <--- Have more txns? <------ Mark txn success & nuke <-+
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from db; incr AS pos.
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Reset backoff.
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This is all tied together by the AppServiceScheduler which DIs the required
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components.
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"""
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from synapse.appservice import ApplicationServiceState
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from twisted.internet import defer
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import logging
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logger = logging.getLogger(__name__)
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class AppServiceScheduler(object):
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""" Public facing API for this module. Does the required DI to tie the
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components together. This also serves as the "event_pool", which in this
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case is a simple array.
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"""
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def __init__(self, clock, store, as_api):
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self.clock = clock
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self.store = store
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self.as_api = as_api
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self.event_grouper = _EventGrouper()
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def create_recoverer(service, callback):
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return _Recoverer(clock, store, as_api, service, callback)
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self.txn_ctrl = _TransactionController(
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clock, store, as_api, self.event_grouper, create_recoverer
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)
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@defer.inlineCallbacks
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def start(self):
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# check for any DOWN ASes and start recoverers for them.
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recoverers = yield _Recoverer.start(
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self.clock, self.store, self.as_api, self.txn_ctrl.on_recovered
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)
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self.txn_ctrl.add_recoverers(recoverers)
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self.txn_ctrl.start_polling()
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def submit_event_for_as(self, service, event):
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self.event_grouper.on_receive(service, event)
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class _EventGrouper(object):
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"""Groups events for the same application service together.
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"""
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def __init__(self):
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self.groups = {} # dict of {service: [events]}
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def on_receive(self, service, event):
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if service not in self.groups:
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self.groups[service] = []
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self.groups[service].append(event)
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def drain_groups(self):
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groups = self.groups
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self.groups = {}
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return groups
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class _TransactionController(object):
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def __init__(self, clock, store, as_api, event_grouper, recoverer_fn):
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self.clock = clock
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self.store = store
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self.as_api = as_api
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self.event_grouper = event_grouper
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self.recoverer_fn = recoverer_fn
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# keep track of how many recoverers there are
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self.recoverers = []
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@defer.inlineCallbacks
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def start_polling(self):
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groups = self.event_grouper.drain_groups()
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for service in groups:
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txn = yield self.store.create_appservice_txn(
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service=service,
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events=groups[service]
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)
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service_is_up = yield self._is_service_up(service)
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if service_is_up:
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sent = yield txn.send(self.as_api)
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if sent:
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txn.complete(self.store)
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else:
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self._start_recoverer(service)
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self.clock.call_later(1, self.start_polling)
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@defer.inlineCallbacks
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def on_recovered(self, recoverer):
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self.recoverers.remove(recoverer)
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logger.info("Successfully recovered application service: %s",
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recoverer.service)
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logger.info("Active recoverers: %s", len(self.recoverers))
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applied_state = yield self.store.set_appservice_state(
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recoverer.service,
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ApplicationServiceState.UP
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)
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if not applied_state:
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logger.error("Failed to apply appservice state UP to service %s",
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recoverer.service)
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def add_recoverers(self, recoverers):
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for r in recoverers:
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self.recoverers.append(r)
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if len(recoverers) > 0:
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logger.info("Active recoverers: %s", len(self.recoverers))
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@defer.inlineCallbacks
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def _start_recoverer(self, service):
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applied_state = yield self.store.set_appservice_state(
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service,
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ApplicationServiceState.DOWN
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)
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if applied_state:
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logger.info(
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"Application service falling behind. Starting recoverer. %s",
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service
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)
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recoverer = self.recoverer_fn(service, self.on_recovered)
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self.add_recoverers([recoverer])
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recoverer.recover()
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else:
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logger.error("Failed to apply appservice state DOWN to service %s",
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service)
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@defer.inlineCallbacks
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def _is_service_up(self, service):
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state = yield self.store.get_appservice_state(service)
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defer.returnValue(state == ApplicationServiceState.UP)
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class _Recoverer(object):
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@staticmethod
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@defer.inlineCallbacks
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def start(clock, store, as_api, callback):
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services = yield store.get_appservices_by_state(
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ApplicationServiceState.DOWN
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)
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recoverers = [
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_Recoverer(clock, store, as_api, s, callback) for s in services
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]
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for r in recoverers:
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r.recover()
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defer.returnValue(recoverers)
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def __init__(self, clock, store, as_api, service, callback):
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self.clock = clock
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self.store = store
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self.as_api = as_api
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self.service = service
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self.callback = callback
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self.backoff_counter = 1
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def recover(self):
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self.clock.call_later((2 ** self.backoff_counter), self.retry)
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@defer.inlineCallbacks
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def retry(self):
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txn = yield self._get_oldest_txn()
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if txn:
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if txn.send(self.as_api):
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txn.complete(self.store)
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# reset the backoff counter and retry immediately
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self.backoff_counter = 1
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yield self.retry()
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else:
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# cap the backoff to be around 18h => (2^16) = 65536 secs
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if self.backoff_counter < 16:
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self.backoff_counter += 1
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self.recover()
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else:
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self._set_service_recovered()
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def _set_service_recovered(self):
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self.callback(self)
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@defer.inlineCallbacks
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def _get_oldest_txn(self):
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txn = yield self.store.get_oldest_unsent_txn(self.service)
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defer.returnValue(txn)
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