summary refs log tree commit diff
path: root/synapse/appservice/scheduler.py
blob: 068d4bd087646ccdd0579ce5df7d4a2e0f880ffc (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
# -*- 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:
             _________
---ASa[e]-->|  Event  |
----ASb[e]->| Grouper |<-poll 1/s--+
--ASa[e]--->|_________|            | ASa[e,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
        self.event_grouper = _EventGrouper()

        def create_recoverer(service, callback):
            return _Recoverer(clock, store, as_api, service, callback)

        self.txn_ctrl = _TransactionController(
            clock, store, as_api, self.event_grouper, create_recoverer
        )

    @defer.inlineCallbacks
    def start(self):
        # 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)
        self.txn_ctrl.start_polling()

    def submit_event_for_as(self, service, event):
        self.event_grouper.on_receive(service, event)


class _EventGrouper(object):
    """Groups events for the same application service together.
    """

    def __init__(self):
        self.groups = {}  # dict of {service: [events]}

    def on_receive(self, service, event):
        if service not in self.groups:
            self.groups[service] = []
        self.groups[service].append(event)

    def drain_groups(self):
        groups = self.groups
        self.groups = {}
        return groups


class _TransactionController(object):

    def __init__(self, clock, store, as_api, event_grouper, recoverer_fn):
        self.clock = clock
        self.store = store
        self.as_api = as_api
        self.event_grouper = event_grouper
        self.recoverer_fn = recoverer_fn
        # keep track of how many recoverers there are
        self.recoverers = []

    @defer.inlineCallbacks
    def start_polling(self):
        groups = self.event_grouper.drain_groups()
        for service in groups:
            txn = yield self.store.create_appservice_txn(
                service=service,
                events=groups[service]
            )
            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)
        self.clock.call_later(1, self.start_polling)

    @defer.inlineCallbacks
    def on_recovered(self, recoverer):
        self.recoverers.remove(recoverer)
        logger.info("Successfully recovered application service: %s",
                    recoverer.service)
        logger.info("Active recoverers: %s", len(self.recoverers))
        applied_state = yield self.store.set_appservice_state(
            recoverer.service,
            ApplicationServiceState.UP
        )
        if not applied_state:
            logger.error("Failed to apply appservice state UP to service %s",
                         recoverer.service)

    def add_recoverers(self, recoverers):
        for r in recoverers:
            self.recoverers.append(r)
        if len(recoverers) > 0:
            logger.info("Active recoverers: %s", len(self.recoverers))

    @defer.inlineCallbacks
    def _start_recoverer(self, service):
        applied_state = yield self.store.set_appservice_state(
            service,
            ApplicationServiceState.DOWN
        )
        if applied_state:
            logger.info(
                "Application service falling behind. Starting recoverer. %s",
                service
            )
            recoverer = self.recoverer_fn(service, self.on_recovered)
            self.add_recoverers([recoverer])
            recoverer.recover()
        else:
            logger.error("Failed to apply appservice state DOWN to service %s",
                         service)

    @defer.inlineCallbacks
    def _is_service_up(self, service):
        state = yield self.store.get_appservice_state(service)
        defer.returnValue(state == ApplicationServiceState.UP)


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:
            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)

    @defer.inlineCallbacks
    def retry(self):
        txn = yield self._get_oldest_txn()
        if txn:
            if txn.send(self.as_api):
                txn.complete(self.store)
                # reset the backoff counter and retry immediately
                self.backoff_counter = 1
                yield self.retry()
            else:
                # cap the backoff to be around 18h => (2^16) = 65536 secs
                if self.backoff_counter < 16:
                    self.backoff_counter += 1
                self.recover()
        else:
            self._set_service_recovered()

    def _set_service_recovered(self):
        self.callback(self)

    @defer.inlineCallbacks
    def _get_oldest_txn(self):
        txn = yield self.store.get_oldest_unsent_txn(self.service)
        defer.returnValue(txn)