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Retry some http replication failures (#12182)

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This allows for the target process to be down for around a minute
which provides time for restarts during synapse upgrades/config updates.

Closes: #12178

Signed off by Nick Mills-Barrett nick@beeper.com
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Nick Mills-Barrett 2022-03-09 14:53:28 +00:00 committed by GitHub
parent dc8d825ef2
commit 180d8ff0d4
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2 changed files with 37 additions and 11 deletions
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1
changelog.d/12182.misc Normal file
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@ -0,0 +1 @@
Retry HTTP replication failures, this should prevent 502's when restarting stateful workers (main, event persisters, stream writers). Contributed by Nick @ Beeper.

39
synapse/replication/http/_base.py
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@ -21,6 +21,7 @@ from typing import TYPE_CHECKING, Any, Awaitable, Callable, Dict, List, Tuple
from prometheus_client import Counter, Gauge
from twisted.internet.error import ConnectError, DNSLookupError
from twisted.web.server import Request
from synapse.api.errors import HttpResponseException, SynapseError
@ -87,6 +88,10 @@ class ReplicationEndpoint(metaclass=abc.ABCMeta):
`_handle_request` must return a Deferred.
RETRY_ON_TIMEOUT(bool): Whether or not to retry the request when a 504
is received.
RETRY_ON_CONNECT_ERROR (bool): Whether or not to retry the request when
a connection error is received.
RETRY_ON_CONNECT_ERROR_ATTEMPTS (int): Number of attempts to retry when
receiving connection errors, each will backoff exponentially longer.
"""
NAME: str = abc.abstractproperty() # type: ignore
@ -94,6 +99,8 @@ class ReplicationEndpoint(metaclass=abc.ABCMeta):
METHOD = "POST"
CACHE = True
RETRY_ON_TIMEOUT = True
RETRY_ON_CONNECT_ERROR = True
RETRY_ON_CONNECT_ERROR_ATTEMPTS = 5 # =63s (2^6-1)
def __init__(self, hs: "HomeServer"):
if self.CACHE:
@ -236,18 +243,20 @@ class ReplicationEndpoint(metaclass=abc.ABCMeta):
"/".join(url_args),
)
headers: Dict[bytes, List[bytes]] = {}
# Add an authorization header, if configured.
if replication_secret:
headers[b"Authorization"] = [b"Bearer " + replication_secret]
opentracing.inject_header_dict(headers, check_destination=False)
try:
# Keep track of attempts made so we can bail if we don't manage to
# connect to the target after N tries.
attempts = 0
# We keep retrying the same request for timeouts. This is so that we
# have a good idea that the request has either succeeded or failed
# on the master, and so whether we should clean up or not.
while True:
headers: Dict[bytes, List[bytes]] = {}
# Add an authorization header, if configured.
if replication_secret:
headers[b"Authorization"] = [
b"Bearer " + replication_secret
]
opentracing.inject_header_dict(headers, check_destination=False)
try:
result = await request_func(uri, data, headers=headers)
break
@ -260,6 +269,22 @@ class ReplicationEndpoint(metaclass=abc.ABCMeta):
# If we timed out we probably don't need to worry about backing
# off too much, but lets just wait a little anyway.
await clock.sleep(1)
except (ConnectError, DNSLookupError) as e:
if not cls.RETRY_ON_CONNECT_ERROR:
raise
if attempts > cls.RETRY_ON_CONNECT_ERROR_ATTEMPTS:
raise
delay = 2 ** attempts
logger.warning(
"%s request connection failed; retrying in %ds: %r",
cls.NAME,
delay,
e,
)
await clock.sleep(delay)
attempts += 1
except HttpResponseException as e:
# We convert to SynapseError as we know that it was a SynapseError
# on the main process that we should send to the client. (And