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
231
232
233
234
235
236
237
238
|
# -*- coding: utf-8 -*-
# Copyright 2015, 2016 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.
import logging
import random
from twisted.internet import defer
import synapse.logging.context
from synapse.api.errors import CodeMessageException
logger = logging.getLogger(__name__)
# the initial backoff, after the first transaction fails
MIN_RETRY_INTERVAL = 10 * 60 * 1000
# how much we multiply the backoff by after each subsequent fail
RETRY_MULTIPLIER = 5
# a cap on the backoff. (Essentially none)
MAX_RETRY_INTERVAL = 2 ** 62
class NotRetryingDestination(Exception):
def __init__(self, retry_last_ts, retry_interval, destination):
"""Raised by the limiter (and federation client) to indicate that we are
are deliberately not attempting to contact a given server.
Args:
retry_last_ts (int): the unix ts in milliseconds of our last attempt
to contact the server. 0 indicates that the last attempt was
successful or that we've never actually attempted to connect.
retry_interval (int): the time in milliseconds to wait until the next
attempt.
destination (str): the domain in question
"""
msg = "Not retrying server %s." % (destination,)
super(NotRetryingDestination, self).__init__(msg)
self.retry_last_ts = retry_last_ts
self.retry_interval = retry_interval
self.destination = destination
@defer.inlineCallbacks
def get_retry_limiter(destination, clock, store, ignore_backoff=False, **kwargs):
"""For a given destination check if we have previously failed to
send a request there and are waiting before retrying the destination.
If we are not ready to retry the destination, this will raise a
NotRetryingDestination exception. Otherwise, will return a Context Manager
that will mark the destination as down if an exception is thrown (excluding
CodeMessageException with code < 500)
Args:
destination (str): name of homeserver
clock (synapse.util.clock): timing source
store (synapse.storage.transactions.TransactionStore): datastore
ignore_backoff (bool): true to ignore the historical backoff data and
try the request anyway. We will still reset the retry_interval on success.
Example usage:
try:
limiter = yield get_retry_limiter(destination, clock, store)
with limiter:
response = yield do_request()
except NotRetryingDestination:
# We aren't ready to retry that destination.
raise
"""
failure_ts = None
retry_last_ts, retry_interval = (0, 0)
retry_timings = yield store.get_destination_retry_timings(destination)
if retry_timings:
failure_ts = retry_timings["failure_ts"]
retry_last_ts, retry_interval = (
retry_timings["retry_last_ts"],
retry_timings["retry_interval"],
)
now = int(clock.time_msec())
if not ignore_backoff and retry_last_ts + retry_interval > now:
raise NotRetryingDestination(
retry_last_ts=retry_last_ts,
retry_interval=retry_interval,
destination=destination,
)
# if we are ignoring the backoff data, we should also not increment the backoff
# when we get another failure - otherwise a server can very quickly reach the
# maximum backoff even though it might only have been down briefly
backoff_on_failure = not ignore_backoff
return RetryDestinationLimiter(
destination,
clock,
store,
failure_ts,
retry_interval,
backoff_on_failure=backoff_on_failure,
**kwargs
)
class RetryDestinationLimiter(object):
def __init__(
self,
destination,
clock,
store,
failure_ts,
retry_interval,
backoff_on_404=False,
backoff_on_failure=True,
):
"""Marks the destination as "down" if an exception is thrown in the
context, except for CodeMessageException with code < 500.
If no exception is raised, marks the destination as "up".
Args:
destination (str)
clock (Clock)
store (DataStore)
failure_ts (int|None): when this destination started failing (in ms since
the epoch), or zero if the last request was successful
retry_interval (int): The next retry interval taken from the
database in milliseconds, or zero if the last request was
successful.
backoff_on_404 (bool): Back off if we get a 404
backoff_on_failure (bool): set to False if we should not increase the
retry interval on a failure.
"""
self.clock = clock
self.store = store
self.destination = destination
self.failure_ts = failure_ts
self.retry_interval = retry_interval
self.backoff_on_404 = backoff_on_404
self.backoff_on_failure = backoff_on_failure
def __enter__(self):
pass
def __exit__(self, exc_type, exc_val, exc_tb):
valid_err_code = False
if exc_type is None:
valid_err_code = True
elif not issubclass(exc_type, Exception):
# avoid treating exceptions which don't derive from Exception as
# failures; this is mostly so as not to catch defer._DefGen.
valid_err_code = True
elif issubclass(exc_type, CodeMessageException):
# Some error codes are perfectly fine for some APIs, whereas other
# APIs may expect to never received e.g. a 404. It's important to
# handle 404 as some remote servers will return a 404 when the HS
# has been decommissioned.
# If we get a 401, then we should probably back off since they
# won't accept our requests for at least a while.
# 429 is us being aggressively rate limited, so lets rate limit
# ourselves.
if exc_val.code == 404 and self.backoff_on_404:
valid_err_code = False
elif exc_val.code in (401, 429):
valid_err_code = False
elif exc_val.code < 500:
valid_err_code = True
else:
valid_err_code = False
if valid_err_code:
# We connected successfully.
if not self.retry_interval:
return
logger.debug(
"Connection to %s was successful; clearing backoff", self.destination
)
self.failure_ts = None
retry_last_ts = 0
self.retry_interval = 0
elif not self.backoff_on_failure:
return
else:
# We couldn't connect.
if self.retry_interval:
self.retry_interval = int(
self.retry_interval * RETRY_MULTIPLIER * random.uniform(0.8, 1.4)
)
if self.retry_interval >= MAX_RETRY_INTERVAL:
self.retry_interval = MAX_RETRY_INTERVAL
else:
self.retry_interval = MIN_RETRY_INTERVAL
logger.info(
"Connection to %s was unsuccessful (%s(%s)); backoff now %i",
self.destination,
exc_type,
exc_val,
self.retry_interval,
)
retry_last_ts = int(self.clock.time_msec())
if self.failure_ts is None:
self.failure_ts = retry_last_ts
@defer.inlineCallbacks
def store_retry_timings():
try:
yield self.store.set_destination_retry_timings(
self.destination,
self.failure_ts,
retry_last_ts,
self.retry_interval,
)
except Exception:
logger.exception("Failed to store destination_retry_timings")
# we deliberately do this in the background.
synapse.logging.context.run_in_background(store_retry_timings)
|
