659 lines
24 KiB
Python
659 lines
24 KiB
Python
# Copyright 2014-2016 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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from typing import (
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TYPE_CHECKING,
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AsyncContextManager,
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Awaitable,
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Callable,
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Dict,
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Iterable,
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Optional,
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)
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import attr
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from synapse.metrics.background_process_metrics import run_as_background_process
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from synapse.storage.types import Connection
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from synapse.types import JsonDict
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from synapse.util import Clock, json_encoder
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from . import engines
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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from synapse.storage.database import DatabasePool, LoggingTransaction
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logger = logging.getLogger(__name__)
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ON_UPDATE_CALLBACK = Callable[[str, str, bool], AsyncContextManager[int]]
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DEFAULT_BATCH_SIZE_CALLBACK = Callable[[str, str], Awaitable[int]]
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MIN_BATCH_SIZE_CALLBACK = Callable[[str, str], Awaitable[int]]
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@attr.s(slots=True, frozen=True, auto_attribs=True)
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class _BackgroundUpdateHandler:
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"""A handler for a given background update.
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Attributes:
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callback: The function to call to make progress on the background
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update.
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oneshot: Wether the update is likely to happen all in one go, ignoring
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the supplied target duration, e.g. index creation. This is used by
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the update controller to help correctly schedule the update.
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"""
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callback: Callable[[JsonDict, int], Awaitable[int]]
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oneshot: bool = False
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class _BackgroundUpdateContextManager:
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BACKGROUND_UPDATE_INTERVAL_MS = 1000
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BACKGROUND_UPDATE_DURATION_MS = 100
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def __init__(self, sleep: bool, clock: Clock):
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self._sleep = sleep
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self._clock = clock
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async def __aenter__(self) -> int:
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if self._sleep:
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await self._clock.sleep(self.BACKGROUND_UPDATE_INTERVAL_MS / 1000)
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return self.BACKGROUND_UPDATE_DURATION_MS
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async def __aexit__(self, *exc) -> None:
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pass
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class BackgroundUpdatePerformance:
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"""Tracks the how long a background update is taking to update its items"""
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def __init__(self, name: str):
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self.name = name
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self.total_item_count = 0
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self.total_duration_ms = 0.0
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self.avg_item_count = 0.0
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self.avg_duration_ms = 0.0
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def update(self, item_count: int, duration_ms: float) -> None:
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"""Update the stats after doing an update"""
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self.total_item_count += item_count
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self.total_duration_ms += duration_ms
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# Exponential moving averages for the number of items updated and
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# the duration.
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self.avg_item_count += 0.1 * (item_count - self.avg_item_count)
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self.avg_duration_ms += 0.1 * (duration_ms - self.avg_duration_ms)
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def average_items_per_ms(self) -> Optional[float]:
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"""An estimate of how long it takes to do a single update.
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Returns:
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A duration in ms as a float
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"""
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if self.avg_duration_ms == 0:
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return 0
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elif self.total_item_count == 0:
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return None
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else:
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# Use the exponential moving average so that we can adapt to
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# changes in how long the update process takes.
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return float(self.avg_item_count) / float(self.avg_duration_ms)
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def total_items_per_ms(self) -> Optional[float]:
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"""An estimate of how long it takes to do a single update.
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Returns:
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A duration in ms as a float
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"""
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if self.total_duration_ms == 0:
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return 0
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elif self.total_item_count == 0:
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return None
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else:
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return float(self.total_item_count) / float(self.total_duration_ms)
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class BackgroundUpdater:
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"""Background updates are updates to the database that run in the
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background. Each update processes a batch of data at once. We attempt to
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limit the impact of each update by monitoring how long each batch takes to
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process and autotuning the batch size.
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"""
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MINIMUM_BACKGROUND_BATCH_SIZE = 1
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DEFAULT_BACKGROUND_BATCH_SIZE = 100
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def __init__(self, hs: "HomeServer", database: "DatabasePool"):
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self._clock = hs.get_clock()
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self.db_pool = database
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self._database_name = database.name()
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# if a background update is currently running, its name.
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self._current_background_update: Optional[str] = None
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self._on_update_callback: Optional[ON_UPDATE_CALLBACK] = None
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self._default_batch_size_callback: Optional[DEFAULT_BATCH_SIZE_CALLBACK] = None
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self._min_batch_size_callback: Optional[MIN_BATCH_SIZE_CALLBACK] = None
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self._background_update_performance: Dict[str, BackgroundUpdatePerformance] = {}
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self._background_update_handlers: Dict[str, _BackgroundUpdateHandler] = {}
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self._all_done = False
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# Whether we're currently running updates
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self._running = False
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# Whether background updates are enabled. This allows us to
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# enable/disable background updates via the admin API.
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self.enabled = True
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def register_update_controller_callbacks(
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self,
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on_update: ON_UPDATE_CALLBACK,
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default_batch_size: Optional[DEFAULT_BATCH_SIZE_CALLBACK] = None,
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min_batch_size: Optional[DEFAULT_BATCH_SIZE_CALLBACK] = None,
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) -> None:
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"""Register callbacks from a module for each hook."""
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if self._on_update_callback is not None:
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logger.warning(
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"More than one module tried to register callbacks for controlling"
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" background updates. Only the callbacks registered by the first module"
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" (in order of appearance in Synapse's configuration file) that tried to"
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" do so will be called."
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)
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return
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self._on_update_callback = on_update
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if default_batch_size is not None:
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self._default_batch_size_callback = default_batch_size
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if min_batch_size is not None:
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self._min_batch_size_callback = min_batch_size
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def _get_context_manager_for_update(
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self,
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sleep: bool,
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update_name: str,
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database_name: str,
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oneshot: bool,
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) -> AsyncContextManager[int]:
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"""Get a context manager to run a background update with.
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If a module has registered a `update_handler` callback, use the context manager
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it returns.
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Otherwise, returns a context manager that will return a default value, optionally
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sleeping if needed.
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Args:
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sleep: Whether we can sleep between updates.
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update_name: The name of the update.
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database_name: The name of the database the update is being run on.
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oneshot: Whether the update will complete all in one go, e.g. index creation.
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In such cases the returned target duration is ignored.
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Returns:
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The target duration in milliseconds that the background update should run for.
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Note: this is a *target*, and an iteration may take substantially longer or
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shorter.
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"""
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if self._on_update_callback is not None:
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return self._on_update_callback(update_name, database_name, oneshot)
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return _BackgroundUpdateContextManager(sleep, self._clock)
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async def _default_batch_size(self, update_name: str, database_name: str) -> int:
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"""The batch size to use for the first iteration of a new background
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update.
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"""
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if self._default_batch_size_callback is not None:
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return await self._default_batch_size_callback(update_name, database_name)
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return self.DEFAULT_BACKGROUND_BATCH_SIZE
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async def _min_batch_size(self, update_name: str, database_name: str) -> int:
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"""A lower bound on the batch size of a new background update.
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Used to ensure that progress is always made. Must be greater than 0.
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"""
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if self._min_batch_size_callback is not None:
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return await self._min_batch_size_callback(update_name, database_name)
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return self.MINIMUM_BACKGROUND_BATCH_SIZE
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def get_current_update(self) -> Optional[BackgroundUpdatePerformance]:
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"""Returns the current background update, if any."""
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update_name = self._current_background_update
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if not update_name:
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return None
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perf = self._background_update_performance.get(update_name)
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if not perf:
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perf = BackgroundUpdatePerformance(update_name)
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return perf
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def start_doing_background_updates(self) -> None:
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if self.enabled:
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# if we start a new background update, not all updates are done.
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self._all_done = False
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run_as_background_process("background_updates", self.run_background_updates)
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async def run_background_updates(self, sleep: bool = True) -> None:
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if self._running or not self.enabled:
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return
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self._running = True
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try:
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logger.info("Starting background schema updates")
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while self.enabled:
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try:
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result = await self.do_next_background_update(sleep)
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except Exception:
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logger.exception("Error doing update")
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else:
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if result:
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logger.info(
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"No more background updates to do."
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" Unscheduling background update task."
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)
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self._all_done = True
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return None
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finally:
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self._running = False
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async def has_completed_background_updates(self) -> bool:
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"""Check if all the background updates have completed
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Returns:
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True if all background updates have completed
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"""
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# if we've previously determined that there is nothing left to do, that
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# is easy
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if self._all_done:
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return True
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# obviously, if we are currently processing an update, we're not done.
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if self._current_background_update:
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return False
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# otherwise, check if there are updates to be run. This is important,
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# as we may be running on a worker which doesn't perform the bg updates
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# itself, but still wants to wait for them to happen.
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updates = await self.db_pool.simple_select_onecol(
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"background_updates",
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keyvalues=None,
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retcol="1",
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desc="has_completed_background_updates",
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)
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if not updates:
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self._all_done = True
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return True
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return False
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async def has_completed_background_update(self, update_name: str) -> bool:
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"""Check if the given background update has finished running."""
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if self._all_done:
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return True
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if update_name == self._current_background_update:
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return False
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update_exists = await self.db_pool.simple_select_one_onecol(
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"background_updates",
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keyvalues={"update_name": update_name},
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retcol="1",
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desc="has_completed_background_update",
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allow_none=True,
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)
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return not update_exists
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async def do_next_background_update(self, sleep: bool = True) -> bool:
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"""Does some amount of work on the next queued background update
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Returns once some amount of work is done.
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Args:
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sleep: Whether to limit how quickly we run background updates or
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not.
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Returns:
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True if we have finished running all the background updates, otherwise False
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"""
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def get_background_updates_txn(txn):
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txn.execute(
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"""
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SELECT update_name, depends_on FROM background_updates
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ORDER BY ordering, update_name
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"""
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)
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return self.db_pool.cursor_to_dict(txn)
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if not self._current_background_update:
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all_pending_updates = await self.db_pool.runInteraction(
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"background_updates",
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get_background_updates_txn,
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)
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if not all_pending_updates:
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# no work left to do
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return True
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# find the first update which isn't dependent on another one in the queue.
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pending = {update["update_name"] for update in all_pending_updates}
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for upd in all_pending_updates:
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depends_on = upd["depends_on"]
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if not depends_on or depends_on not in pending:
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break
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logger.info(
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"Not starting on bg update %s until %s is done",
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upd["update_name"],
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depends_on,
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)
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else:
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# if we get to the end of that for loop, there is a problem
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raise Exception(
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"Unable to find a background update which doesn't depend on "
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"another: dependency cycle?"
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)
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self._current_background_update = upd["update_name"]
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# We have a background update to run, otherwise we would have returned
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# early.
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assert self._current_background_update is not None
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update_info = self._background_update_handlers[self._current_background_update]
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async with self._get_context_manager_for_update(
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sleep=sleep,
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update_name=self._current_background_update,
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database_name=self._database_name,
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oneshot=update_info.oneshot,
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) as desired_duration_ms:
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await self._do_background_update(desired_duration_ms)
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return False
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async def _do_background_update(self, desired_duration_ms: float) -> int:
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assert self._current_background_update is not None
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update_name = self._current_background_update
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logger.info("Starting update batch on background update '%s'", update_name)
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update_handler = self._background_update_handlers[update_name].callback
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performance = self._background_update_performance.get(update_name)
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if performance is None:
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performance = BackgroundUpdatePerformance(update_name)
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self._background_update_performance[update_name] = performance
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items_per_ms = performance.average_items_per_ms()
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if items_per_ms is not None:
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batch_size = int(desired_duration_ms * items_per_ms)
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# Clamp the batch size so that we always make progress
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batch_size = max(
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batch_size,
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await self._min_batch_size(update_name, self._database_name),
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)
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else:
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batch_size = await self._default_batch_size(
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update_name, self._database_name
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)
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progress_json = await self.db_pool.simple_select_one_onecol(
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"background_updates",
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keyvalues={"update_name": update_name},
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retcol="progress_json",
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)
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# Avoid a circular import.
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from synapse.storage._base import db_to_json
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progress = db_to_json(progress_json)
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time_start = self._clock.time_msec()
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items_updated = await update_handler(progress, batch_size)
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time_stop = self._clock.time_msec()
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duration_ms = time_stop - time_start
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performance.update(items_updated, duration_ms)
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logger.info(
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"Running background update %r. Processed %r items in %rms."
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" (total_rate=%r/ms, current_rate=%r/ms, total_updated=%r, batch_size=%r)",
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update_name,
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items_updated,
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duration_ms,
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performance.total_items_per_ms(),
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performance.average_items_per_ms(),
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performance.total_item_count,
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batch_size,
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)
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return len(self._background_update_performance)
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def register_background_update_handler(
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self,
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update_name: str,
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update_handler: Callable[[JsonDict, int], Awaitable[int]],
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):
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"""Register a handler for doing a background update.
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The handler should take two arguments:
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* A dict of the current progress
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* An integer count of the number of items to update in this batch.
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The handler should return a deferred or coroutine which returns an integer count
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of items updated.
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The handler is responsible for updating the progress of the update.
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Args:
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update_name: The name of the update that this code handles.
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update_handler: The function that does the update.
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"""
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self._background_update_handlers[update_name] = _BackgroundUpdateHandler(
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update_handler
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)
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def register_noop_background_update(self, update_name: str) -> None:
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"""Register a noop handler for a background update.
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This is useful when we previously did a background update, but no
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longer wish to do the update. In this case the background update should
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be removed from the schema delta files, but there may still be some
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users who have the background update queued, so this method should
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also be called to clear the update.
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Args:
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update_name: Name of update
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"""
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async def noop_update(progress: JsonDict, batch_size: int) -> int:
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await self._end_background_update(update_name)
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return 1
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self.register_background_update_handler(update_name, noop_update)
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def register_background_index_update(
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self,
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update_name: str,
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index_name: str,
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table: str,
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columns: Iterable[str],
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where_clause: Optional[str] = None,
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unique: bool = False,
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psql_only: bool = False,
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) -> None:
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"""Helper for store classes to do a background index addition
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To use:
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1. use a schema delta file to add a background update. Example:
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INSERT INTO background_updates (update_name, progress_json) VALUES
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('my_new_index', '{}');
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2. In the Store constructor, call this method
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Args:
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update_name: update_name to register for
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index_name: name of index to add
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table: table to add index to
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columns: columns/expressions to include in index
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unique: true to make a UNIQUE index
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psql_only: true to only create this index on psql databases (useful
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for virtual sqlite tables)
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"""
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def create_index_psql(conn: Connection) -> None:
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conn.rollback()
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# postgres insists on autocommit for the index
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conn.set_session(autocommit=True) # type: ignore
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try:
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c = conn.cursor()
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# If a previous attempt to create the index was interrupted,
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# we may already have a half-built index. Let's just drop it
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# before trying to create it again.
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sql = "DROP INDEX IF EXISTS %s" % (index_name,)
|
|
logger.debug("[SQL] %s", sql)
|
|
c.execute(sql)
|
|
|
|
sql = (
|
|
"CREATE %(unique)s INDEX CONCURRENTLY %(name)s"
|
|
" ON %(table)s"
|
|
" (%(columns)s) %(where_clause)s"
|
|
) % {
|
|
"unique": "UNIQUE" if unique else "",
|
|
"name": index_name,
|
|
"table": table,
|
|
"columns": ", ".join(columns),
|
|
"where_clause": "WHERE " + where_clause if where_clause else "",
|
|
}
|
|
logger.debug("[SQL] %s", sql)
|
|
c.execute(sql)
|
|
finally:
|
|
conn.set_session(autocommit=False) # type: ignore
|
|
|
|
def create_index_sqlite(conn: Connection) -> None:
|
|
# Sqlite doesn't support concurrent creation of indexes.
|
|
#
|
|
# We don't use partial indices on SQLite as it wasn't introduced
|
|
# until 3.8, and wheezy and CentOS 7 have 3.7
|
|
#
|
|
# We assume that sqlite doesn't give us invalid indices; however
|
|
# we may still end up with the index existing but the
|
|
# background_updates not having been recorded if synapse got shut
|
|
# down at the wrong moment - hance we use IF NOT EXISTS. (SQLite
|
|
# has supported CREATE TABLE|INDEX IF NOT EXISTS since 3.3.0.)
|
|
sql = (
|
|
"CREATE %(unique)s INDEX IF NOT EXISTS %(name)s ON %(table)s"
|
|
" (%(columns)s)"
|
|
) % {
|
|
"unique": "UNIQUE" if unique else "",
|
|
"name": index_name,
|
|
"table": table,
|
|
"columns": ", ".join(columns),
|
|
}
|
|
|
|
c = conn.cursor()
|
|
logger.debug("[SQL] %s", sql)
|
|
c.execute(sql)
|
|
|
|
if isinstance(self.db_pool.engine, engines.PostgresEngine):
|
|
runner: Optional[Callable[[Connection], None]] = create_index_psql
|
|
elif psql_only:
|
|
runner = None
|
|
else:
|
|
runner = create_index_sqlite
|
|
|
|
async def updater(progress, batch_size):
|
|
if runner is not None:
|
|
logger.info("Adding index %s to %s", index_name, table)
|
|
await self.db_pool.runWithConnection(runner)
|
|
await self._end_background_update(update_name)
|
|
return 1
|
|
|
|
self._background_update_handlers[update_name] = _BackgroundUpdateHandler(
|
|
updater, oneshot=True
|
|
)
|
|
|
|
async def _end_background_update(self, update_name: str) -> None:
|
|
"""Removes a completed background update task from the queue.
|
|
|
|
Args:
|
|
update_name:: The name of the completed task to remove
|
|
|
|
Returns:
|
|
None, completes once the task is removed.
|
|
"""
|
|
if update_name != self._current_background_update:
|
|
raise Exception(
|
|
"Cannot end background update %s which isn't currently running"
|
|
% update_name
|
|
)
|
|
self._current_background_update = None
|
|
await self.db_pool.simple_delete_one(
|
|
"background_updates", keyvalues={"update_name": update_name}
|
|
)
|
|
|
|
async def _background_update_progress(
|
|
self, update_name: str, progress: dict
|
|
) -> None:
|
|
"""Update the progress of a background update
|
|
|
|
Args:
|
|
update_name: The name of the background update task
|
|
progress: The progress of the update.
|
|
"""
|
|
|
|
await self.db_pool.runInteraction(
|
|
"background_update_progress",
|
|
self._background_update_progress_txn,
|
|
update_name,
|
|
progress,
|
|
)
|
|
|
|
def _background_update_progress_txn(
|
|
self, txn: "LoggingTransaction", update_name: str, progress: JsonDict
|
|
) -> None:
|
|
"""Update the progress of a background update
|
|
|
|
Args:
|
|
txn: The transaction.
|
|
update_name: The name of the background update task
|
|
progress: The progress of the update.
|
|
"""
|
|
|
|
progress_json = json_encoder.encode(progress)
|
|
|
|
self.db_pool.simple_update_one_txn(
|
|
txn,
|
|
"background_updates",
|
|
keyvalues={"update_name": update_name},
|
|
updatevalues={"progress_json": progress_json},
|
|
)
|