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Diffstat (limited to 'synapse/appservice/scheduler.py')
| -rw-r--r-- | synapse/appservice/scheduler.py | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/synapse/appservice/scheduler.py b/synapse/appservice/scheduler.py new file mode 100644 index 0000000000..59b0b1f4ac --- /dev/null +++ b/synapse/appservice/scheduler.py @@ -0,0 +1,254 @@ +# -*- coding: utf-8 -*- +# Copyright 2015 OpenMarket 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. +""" +This module controls the reliability for application service transactions. + +The nominal flow through this module looks like: + __________ +1---ASa[e]-->| Service |--> Queue ASa[f] +2----ASb[e]->| Queuer | +3--ASa[f]--->|__________|-----------+ ASa[e], ASb[e] + V + -````````- +------------+ + |````````|<--StoreTxn-|Transaction | + |Database| | Controller |---> SEND TO AS + `--------` +------------+ +What happens on SEND TO AS depends on the state of the Application Service: + - If the AS is marked as DOWN, do nothing. + - If the AS is marked as UP, send the transaction. + * SUCCESS : Increment where the AS is up to txn-wise and nuke the txn + contents from the db. + * FAILURE : Marked AS as DOWN and start Recoverer. + +Recoverer attempts to recover ASes who have died. The flow for this looks like: + ,--------------------- backoff++ --------------. + V | + START ---> Wait exp ------> Get oldest txn ID from ----> FAILURE + backoff DB and try to send it + ^ |___________ +Mark AS as | V +UP & quit +---------- YES SUCCESS + | | | + NO <--- Have more txns? <------ Mark txn success & nuke <-+ + from db; incr AS pos. + Reset backoff. + +This is all tied together by the AppServiceScheduler which DIs the required +components. +""" + +from synapse.appservice import ApplicationServiceState +from twisted.internet import defer +import logging + +logger = logging.getLogger(__name__) + + +class AppServiceScheduler(object): + """ Public facing API for this module. Does the required DI to tie the + components together. This also serves as the "event_pool", which in this + case is a simple array. + """ + + def __init__(self, clock, store, as_api): + self.clock = clock + self.store = store + self.as_api = as_api + + def create_recoverer(service, callback): + return _Recoverer(clock, store, as_api, service, callback) + + self.txn_ctrl = _TransactionController( + clock, store, as_api, create_recoverer + ) + self.queuer = _ServiceQueuer(self.txn_ctrl) + + @defer.inlineCallbacks + def start(self): + logger.info("Starting appservice scheduler") + # check for any DOWN ASes and start recoverers for them. + recoverers = yield _Recoverer.start( + self.clock, self.store, self.as_api, self.txn_ctrl.on_recovered + ) + self.txn_ctrl.add_recoverers(recoverers) + + def submit_event_for_as(self, service, event): + self.queuer.enqueue(service, event) + + +class _ServiceQueuer(object): + """Queues events for the same application service together, sending + transactions as soon as possible. Once a transaction is sent successfully, + this schedules any other events in the queue to run. + """ + + def __init__(self, txn_ctrl): + self.queued_events = {} # dict of {service_id: [events]} + self.pending_requests = {} # dict of {service_id: Deferred} + self.txn_ctrl = txn_ctrl + + def enqueue(self, service, event): + # if this service isn't being sent something + if not self.pending_requests.get(service.id): + self._send_request(service, [event]) + else: + # add to queue for this service + if service.id not in self.queued_events: + self.queued_events[service.id] = [] + self.queued_events[service.id].append(event) + + def _send_request(self, service, events): + # send request and add callbacks + d = self.txn_ctrl.send(service, events) + d.addBoth(self._on_request_finish) + d.addErrback(self._on_request_fail) + self.pending_requests[service.id] = d + + def _on_request_finish(self, service): + self.pending_requests[service.id] = None + # if there are queued events, then send them. + if (service.id in self.queued_events + and len(self.queued_events[service.id]) > 0): + self._send_request(service, self.queued_events[service.id]) + self.queued_events[service.id] = [] + + def _on_request_fail(self, err): + logger.error("AS request failed: %s", err) + + +class _TransactionController(object): + + def __init__(self, clock, store, as_api, recoverer_fn): + self.clock = clock + self.store = store + self.as_api = as_api + self.recoverer_fn = recoverer_fn + # keep track of how many recoverers there are + self.recoverers = [] + + @defer.inlineCallbacks + def send(self, service, events): + try: + txn = yield self.store.create_appservice_txn( + service=service, + events=events + ) + service_is_up = yield self._is_service_up(service) + if service_is_up: + sent = yield txn.send(self.as_api) + if sent: + txn.complete(self.store) + else: + self._start_recoverer(service) + except Exception as e: + logger.exception(e) + self._start_recoverer(service) + # request has finished + defer.returnValue(service) + + @defer.inlineCallbacks + def on_recovered(self, recoverer): + self.recoverers.remove(recoverer) + logger.info("Successfully recovered application service AS ID %s", + recoverer.service.id) + logger.info("Remaining active recoverers: %s", len(self.recoverers)) + yield self.store.set_appservice_state( + recoverer.service, + ApplicationServiceState.UP + ) + + def add_recoverers(self, recoverers): + for r in recoverers: + self.recoverers.append(r) + if len(recoverers) > 0: + logger.info("New active recoverers: %s", len(self.recoverers)) + + @defer.inlineCallbacks + def _start_recoverer(self, service): + yield self.store.set_appservice_state( + service, + ApplicationServiceState.DOWN + ) + logger.info( + "Application service falling behind. Starting recoverer. AS ID %s", + service.id + ) + recoverer = self.recoverer_fn(service, self.on_recovered) + self.add_recoverers([recoverer]) + recoverer.recover() + + @defer.inlineCallbacks + def _is_service_up(self, service): + state = yield self.store.get_appservice_state(service) + defer.returnValue(state == ApplicationServiceState.UP or state is None) + + +class _Recoverer(object): + + @staticmethod + @defer.inlineCallbacks + def start(clock, store, as_api, callback): + services = yield store.get_appservices_by_state( + ApplicationServiceState.DOWN + ) + recoverers = [ + _Recoverer(clock, store, as_api, s, callback) for s in services + ] + for r in recoverers: + logger.info("Starting recoverer for AS ID %s which was marked as " + "DOWN", r.service.id) + r.recover() + defer.returnValue(recoverers) + + def __init__(self, clock, store, as_api, service, callback): + self.clock = clock + self.store = store + self.as_api = as_api + self.service = service + self.callback = callback + self.backoff_counter = 1 + + def recover(self): + self.clock.call_later((2 ** self.backoff_counter), self.retry) + + def _backoff(self): + # cap the backoff to be around 18h => (2^16) = 65536 secs + if self.backoff_counter < 16: + self.backoff_counter += 1 + self.recover() + + @defer.inlineCallbacks + def retry(self): + try: + txn = yield self.store.get_oldest_unsent_txn(self.service) + if txn: + logger.info("Retrying transaction %s for AS ID %s", + txn.id, txn.service.id) + sent = yield txn.send(self.as_api) + if sent: + yield txn.complete(self.store) + # reset the backoff counter and retry immediately + self.backoff_counter = 1 + yield self.retry() + else: + self._backoff() + else: + self._set_service_recovered() + except Exception as e: + logger.exception(e) + self._backoff() + + def _set_service_recovered(self): + self.callback(self) |