315 lines
12 KiB
Python
315 lines
12 KiB
Python
# Copyright 2015, 2016 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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import logging
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import random
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from types import TracebackType
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from typing import TYPE_CHECKING, Any, Optional, Type
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from synapse.api.errors import CodeMessageException
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from synapse.metrics.background_process_metrics import run_as_background_process
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from synapse.storage import DataStore
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from synapse.types import StrCollection
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from synapse.util import Clock
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if TYPE_CHECKING:
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from synapse.notifier import Notifier
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from synapse.replication.tcp.handler import ReplicationCommandHandler
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logger = logging.getLogger(__name__)
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class NotRetryingDestination(Exception):
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def __init__(self, retry_last_ts: int, retry_interval: int, destination: str):
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"""Raised by the limiter (and federation client) to indicate that we are
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are deliberately not attempting to contact a given server.
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Args:
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retry_last_ts: the unix ts in milliseconds of our last attempt
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to contact the server. 0 indicates that the last attempt was
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successful or that we've never actually attempted to connect.
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retry_interval: the time in milliseconds to wait until the next
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attempt.
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destination: the domain in question
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"""
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msg = f"Not retrying server {destination} because we tried it recently retry_last_ts={retry_last_ts} and we won't check for another retry_interval={retry_interval}ms."
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super().__init__(msg)
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self.retry_last_ts = retry_last_ts
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self.retry_interval = retry_interval
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self.destination = destination
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async def get_retry_limiter(
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destination: str,
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clock: Clock,
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store: DataStore,
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ignore_backoff: bool = False,
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**kwargs: Any,
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) -> "RetryDestinationLimiter":
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"""For a given destination check if we have previously failed to
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send a request there and are waiting before retrying the destination.
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If we are not ready to retry the destination, this will raise a
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NotRetryingDestination exception. Otherwise, will return a Context Manager
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that will mark the destination as down if an exception is thrown (excluding
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CodeMessageException with code < 500)
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Args:
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destination: name of homeserver
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clock: timing source
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store: datastore
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ignore_backoff: true to ignore the historical backoff data and
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try the request anyway. We will still reset the retry_interval on success.
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Example usage:
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try:
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limiter = await get_retry_limiter(destination, clock, store)
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with limiter:
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response = await do_request()
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except NotRetryingDestination:
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# We aren't ready to retry that destination.
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raise
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"""
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failure_ts = None
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retry_last_ts, retry_interval = (0, 0)
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retry_timings = await store.get_destination_retry_timings(destination)
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if retry_timings:
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failure_ts = retry_timings.failure_ts
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retry_last_ts = retry_timings.retry_last_ts
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retry_interval = retry_timings.retry_interval
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now = int(clock.time_msec())
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if not ignore_backoff and retry_last_ts + retry_interval > now:
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raise NotRetryingDestination(
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retry_last_ts=retry_last_ts,
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retry_interval=retry_interval,
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destination=destination,
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)
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# if we are ignoring the backoff data, we should also not increment the backoff
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# when we get another failure - otherwise a server can very quickly reach the
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# maximum backoff even though it might only have been down briefly
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backoff_on_failure = not ignore_backoff
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return RetryDestinationLimiter(
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destination,
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clock,
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store,
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failure_ts,
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retry_interval,
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backoff_on_failure=backoff_on_failure,
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**kwargs,
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)
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async def filter_destinations_by_retry_limiter(
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destinations: StrCollection,
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clock: Clock,
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store: DataStore,
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retry_due_within_ms: int = 0,
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) -> StrCollection:
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"""Filter down the list of destinations to only those that will are either
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alive or due for a retry (within `retry_due_within_ms`)
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"""
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if not destinations:
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return destinations
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retry_timings = await store.get_destination_retry_timings_batch(destinations)
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now = int(clock.time_msec())
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return [
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destination
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for destination, timings in retry_timings.items()
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if timings is None
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or timings.retry_last_ts + timings.retry_interval <= now + retry_due_within_ms
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]
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class RetryDestinationLimiter:
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def __init__(
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self,
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destination: str,
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clock: Clock,
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store: DataStore,
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failure_ts: Optional[int],
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retry_interval: int,
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backoff_on_404: bool = False,
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backoff_on_failure: bool = True,
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notifier: Optional["Notifier"] = None,
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replication_client: Optional["ReplicationCommandHandler"] = None,
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backoff_on_all_error_codes: bool = False,
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):
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"""Marks the destination as "down" if an exception is thrown in the
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context, except for CodeMessageException with code < 500.
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If no exception is raised, marks the destination as "up".
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Args:
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destination
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clock
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store
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failure_ts: when this destination started failing (in ms since
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the epoch), or zero if the last request was successful
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retry_interval: The next retry interval taken from the
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database in milliseconds, or zero if the last request was
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successful.
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backoff_on_404: Back off if we get a 404
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backoff_on_failure: set to False if we should not increase the
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retry interval on a failure.
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notifier: A notifier used to mark servers as up.
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replication_client A replication client used to mark servers as up.
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backoff_on_all_error_codes: Whether we should back off on any
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error code.
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"""
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self.clock = clock
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self.store = store
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self.destination = destination
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self.failure_ts = failure_ts
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self.retry_interval = retry_interval
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self.backoff_on_404 = backoff_on_404
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self.backoff_on_failure = backoff_on_failure
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self.backoff_on_all_error_codes = backoff_on_all_error_codes
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self.notifier = notifier
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self.replication_client = replication_client
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self.destination_min_retry_interval_ms = (
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self.store.hs.config.federation.destination_min_retry_interval_ms
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)
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self.destination_retry_multiplier = (
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self.store.hs.config.federation.destination_retry_multiplier
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)
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self.destination_max_retry_interval_ms = (
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self.store.hs.config.federation.destination_max_retry_interval_ms
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)
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def __enter__(self) -> None:
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pass
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def __exit__(
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self,
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exc_type: Optional[Type[BaseException]],
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exc_val: Optional[BaseException],
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exc_tb: Optional[TracebackType],
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) -> None:
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success = exc_type is None
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valid_err_code = False
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if exc_type is None:
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valid_err_code = True
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elif not issubclass(exc_type, Exception):
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# avoid treating exceptions which don't derive from Exception as
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# failures; this is mostly so as not to catch defer._DefGen.
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valid_err_code = True
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elif isinstance(exc_val, CodeMessageException):
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# Some error codes are perfectly fine for some APIs, whereas other
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# APIs may expect to never received e.g. a 404. It's important to
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# handle 404 as some remote servers will return a 404 when the HS
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# has been decommissioned.
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# If we get a 401, then we should probably back off since they
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# won't accept our requests for at least a while.
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# 429 is us being aggressively rate limited, so lets rate limit
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# ourselves.
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if self.backoff_on_all_error_codes:
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valid_err_code = False
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elif exc_val.code == 404 and self.backoff_on_404:
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valid_err_code = False
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elif exc_val.code in (401, 429):
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valid_err_code = False
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elif exc_val.code < 500:
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valid_err_code = True
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else:
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valid_err_code = False
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# Whether previous requests to the destination had been failing.
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previously_failing = bool(self.failure_ts)
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if success:
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# We connected successfully.
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if not self.retry_interval:
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return
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logger.debug(
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"Connection to %s was successful; clearing backoff", self.destination
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)
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self.failure_ts = None
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retry_last_ts = 0
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self.retry_interval = 0
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elif valid_err_code:
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# We got a potentially valid error code back. We don't reset the
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# timers though, as the other side might actually be down anyway
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# (e.g. some deprovisioned servers will always return a 404 or 403,
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# and we don't want to keep resetting the retry timers for them).
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return
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elif not self.backoff_on_failure:
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return
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else:
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# We couldn't connect.
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if self.retry_interval:
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self.retry_interval = int(
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self.retry_interval
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* self.destination_retry_multiplier
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* random.uniform(0.8, 1.4)
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)
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if self.retry_interval >= self.destination_max_retry_interval_ms:
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self.retry_interval = self.destination_max_retry_interval_ms
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else:
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self.retry_interval = self.destination_min_retry_interval_ms
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logger.info(
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"Connection to %s was unsuccessful (%s(%s)); backoff now %i",
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self.destination,
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exc_type,
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exc_val,
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self.retry_interval,
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)
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retry_last_ts = int(self.clock.time_msec())
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if self.failure_ts is None:
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self.failure_ts = retry_last_ts
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# Whether the current request to the destination had been failing.
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currently_failing = bool(self.failure_ts)
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async def store_retry_timings() -> None:
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try:
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await self.store.set_destination_retry_timings(
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self.destination,
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self.failure_ts,
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retry_last_ts,
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self.retry_interval,
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)
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# If the server was previously failing, but is no longer.
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if previously_failing and not currently_failing:
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if self.notifier:
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# Inform the relevant places that the remote server is back up.
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self.notifier.notify_remote_server_up(self.destination)
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if self.replication_client:
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# Inform other workers that the remote server is up.
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self.replication_client.send_remote_server_up(self.destination)
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except Exception:
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logger.exception("Failed to store destination_retry_timings")
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# we deliberately do this in the background.
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run_as_background_process("store_retry_timings", store_retry_timings)
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