mirror of
https://git.anonymousland.org/anonymousland/synapse.git
synced 2024-12-20 12:54:23 -05:00
655 lines
24 KiB
Python
655 lines
24 KiB
Python
# -*- coding: utf-8 -*-
|
|
# Copyright 2014-2016 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 heapq
|
|
import logging
|
|
import threading
|
|
from collections import deque
|
|
from contextlib import contextmanager
|
|
from typing import Dict, List, Optional, Set, Union
|
|
|
|
import attr
|
|
from typing_extensions import Deque
|
|
|
|
from synapse.metrics.background_process_metrics import run_as_background_process
|
|
from synapse.storage.database import DatabasePool, LoggingTransaction
|
|
from synapse.storage.types import Cursor
|
|
from synapse.storage.util.sequence import PostgresSequenceGenerator
|
|
|
|
logger = logging.getLogger(__name__)
|
|
|
|
|
|
class IdGenerator:
|
|
def __init__(self, db_conn, table, column):
|
|
self._lock = threading.Lock()
|
|
self._next_id = _load_current_id(db_conn, table, column)
|
|
|
|
def get_next(self):
|
|
with self._lock:
|
|
self._next_id += 1
|
|
return self._next_id
|
|
|
|
|
|
def _load_current_id(db_conn, table, column, step=1):
|
|
"""
|
|
|
|
Args:
|
|
db_conn (object):
|
|
table (str):
|
|
column (str):
|
|
step (int):
|
|
|
|
Returns:
|
|
int
|
|
"""
|
|
# debug logging for https://github.com/matrix-org/synapse/issues/7968
|
|
logger.info("initialising stream generator for %s(%s)", table, column)
|
|
cur = db_conn.cursor(txn_name="_load_current_id")
|
|
if step == 1:
|
|
cur.execute("SELECT MAX(%s) FROM %s" % (column, table))
|
|
else:
|
|
cur.execute("SELECT MIN(%s) FROM %s" % (column, table))
|
|
(val,) = cur.fetchone()
|
|
cur.close()
|
|
current_id = int(val) if val else step
|
|
return (max if step > 0 else min)(current_id, step)
|
|
|
|
|
|
class StreamIdGenerator:
|
|
"""Used to generate new stream ids when persisting events while keeping
|
|
track of which transactions have been completed.
|
|
|
|
This allows us to get the "current" stream id, i.e. the stream id such that
|
|
all ids less than or equal to it have completed. This handles the fact that
|
|
persistence of events can complete out of order.
|
|
|
|
Args:
|
|
db_conn(connection): A database connection to use to fetch the
|
|
initial value of the generator from.
|
|
table(str): A database table to read the initial value of the id
|
|
generator from.
|
|
column(str): The column of the database table to read the initial
|
|
value from the id generator from.
|
|
extra_tables(list): List of pairs of database tables and columns to
|
|
use to source the initial value of the generator from. The value
|
|
with the largest magnitude is used.
|
|
step(int): which direction the stream ids grow in. +1 to grow
|
|
upwards, -1 to grow downwards.
|
|
|
|
Usage:
|
|
async with stream_id_gen.get_next() as stream_id:
|
|
# ... persist event ...
|
|
"""
|
|
|
|
def __init__(self, db_conn, table, column, extra_tables=[], step=1):
|
|
assert step != 0
|
|
self._lock = threading.Lock()
|
|
self._step = step
|
|
self._current = _load_current_id(db_conn, table, column, step)
|
|
for table, column in extra_tables:
|
|
self._current = (max if step > 0 else min)(
|
|
self._current, _load_current_id(db_conn, table, column, step)
|
|
)
|
|
self._unfinished_ids = deque() # type: Deque[int]
|
|
|
|
def get_next(self):
|
|
"""
|
|
Usage:
|
|
async with stream_id_gen.get_next() as stream_id:
|
|
# ... persist event ...
|
|
"""
|
|
with self._lock:
|
|
self._current += self._step
|
|
next_id = self._current
|
|
|
|
self._unfinished_ids.append(next_id)
|
|
|
|
@contextmanager
|
|
def manager():
|
|
try:
|
|
yield next_id
|
|
finally:
|
|
with self._lock:
|
|
self._unfinished_ids.remove(next_id)
|
|
|
|
return _AsyncCtxManagerWrapper(manager())
|
|
|
|
def get_next_mult(self, n):
|
|
"""
|
|
Usage:
|
|
async with stream_id_gen.get_next(n) as stream_ids:
|
|
# ... persist events ...
|
|
"""
|
|
with self._lock:
|
|
next_ids = range(
|
|
self._current + self._step,
|
|
self._current + self._step * (n + 1),
|
|
self._step,
|
|
)
|
|
self._current += n * self._step
|
|
|
|
for next_id in next_ids:
|
|
self._unfinished_ids.append(next_id)
|
|
|
|
@contextmanager
|
|
def manager():
|
|
try:
|
|
yield next_ids
|
|
finally:
|
|
with self._lock:
|
|
for next_id in next_ids:
|
|
self._unfinished_ids.remove(next_id)
|
|
|
|
return _AsyncCtxManagerWrapper(manager())
|
|
|
|
def get_current_token(self) -> int:
|
|
"""Returns the maximum stream id such that all stream ids less than or
|
|
equal to it have been successfully persisted.
|
|
|
|
Returns:
|
|
The maximum stream id.
|
|
"""
|
|
with self._lock:
|
|
if self._unfinished_ids:
|
|
return self._unfinished_ids[0] - self._step
|
|
|
|
return self._current
|
|
|
|
def get_current_token_for_writer(self, instance_name: str) -> int:
|
|
"""Returns the position of the given writer.
|
|
|
|
For streams with single writers this is equivalent to
|
|
`get_current_token`.
|
|
"""
|
|
return self.get_current_token()
|
|
|
|
|
|
class MultiWriterIdGenerator:
|
|
"""An ID generator that tracks a stream that can have multiple writers.
|
|
|
|
Uses a Postgres sequence to coordinate ID assignment, but positions of other
|
|
writers will only get updated when `advance` is called (by replication).
|
|
|
|
Note: Only works with Postgres.
|
|
|
|
Args:
|
|
db_conn
|
|
db
|
|
stream_name: A name for the stream.
|
|
instance_name: The name of this instance.
|
|
table: Database table associated with stream.
|
|
instance_column: Column that stores the row's writer's instance name
|
|
id_column: Column that stores the stream ID.
|
|
sequence_name: The name of the postgres sequence used to generate new
|
|
IDs.
|
|
writers: A list of known writers to use to populate current positions
|
|
on startup. Can be empty if nothing uses `get_current_token` or
|
|
`get_positions` (e.g. caches stream).
|
|
positive: Whether the IDs are positive (true) or negative (false).
|
|
When using negative IDs we go backwards from -1 to -2, -3, etc.
|
|
"""
|
|
|
|
def __init__(
|
|
self,
|
|
db_conn,
|
|
db: DatabasePool,
|
|
stream_name: str,
|
|
instance_name: str,
|
|
table: str,
|
|
instance_column: str,
|
|
id_column: str,
|
|
sequence_name: str,
|
|
writers: List[str],
|
|
positive: bool = True,
|
|
):
|
|
self._db = db
|
|
self._stream_name = stream_name
|
|
self._instance_name = instance_name
|
|
self._positive = positive
|
|
self._writers = writers
|
|
self._return_factor = 1 if positive else -1
|
|
|
|
# We lock as some functions may be called from DB threads.
|
|
self._lock = threading.Lock()
|
|
|
|
# Note: If we are a negative stream then we still store all the IDs as
|
|
# positive to make life easier for us, and simply negate the IDs when we
|
|
# return them.
|
|
self._current_positions = {} # type: Dict[str, int]
|
|
|
|
# Set of local IDs that we're still processing. The current position
|
|
# should be less than the minimum of this set (if not empty).
|
|
self._unfinished_ids = set() # type: Set[int]
|
|
|
|
# Set of local IDs that we've processed that are larger than the current
|
|
# position, due to there being smaller unpersisted IDs.
|
|
self._finished_ids = set() # type: Set[int]
|
|
|
|
# We track the max position where we know everything before has been
|
|
# persisted. This is done by a) looking at the min across all instances
|
|
# and b) noting that if we have seen a run of persisted positions
|
|
# without gaps (e.g. 5, 6, 7) then we can skip forward (e.g. to 7).
|
|
#
|
|
# Note: There is no guarentee that the IDs generated by the sequence
|
|
# will be gapless; gaps can form when e.g. a transaction was rolled
|
|
# back. This means that sometimes we won't be able to skip forward the
|
|
# position even though everything has been persisted. However, since
|
|
# gaps should be relatively rare it's still worth doing the book keeping
|
|
# that allows us to skip forwards when there are gapless runs of
|
|
# positions.
|
|
#
|
|
# We start at 1 here as a) the first generated stream ID will be 2, and
|
|
# b) other parts of the code assume that stream IDs are strictly greater
|
|
# than 0.
|
|
self._persisted_upto_position = (
|
|
min(self._current_positions.values()) if self._current_positions else 1
|
|
)
|
|
self._known_persisted_positions = [] # type: List[int]
|
|
|
|
self._sequence_gen = PostgresSequenceGenerator(sequence_name)
|
|
|
|
# We check that the table and sequence haven't diverged.
|
|
self._sequence_gen.check_consistency(
|
|
db_conn, table=table, id_column=id_column, positive=positive
|
|
)
|
|
|
|
# This goes and fills out the above state from the database.
|
|
self._load_current_ids(db_conn, table, instance_column, id_column)
|
|
|
|
def _load_current_ids(
|
|
self, db_conn, table: str, instance_column: str, id_column: str
|
|
):
|
|
cur = db_conn.cursor(txn_name="_load_current_ids")
|
|
|
|
# Load the current positions of all writers for the stream.
|
|
if self._writers:
|
|
# We delete any stale entries in the positions table. This is
|
|
# important if we add back a writer after a long time; we want to
|
|
# consider that a "new" writer, rather than using the old stale
|
|
# entry here.
|
|
sql = """
|
|
DELETE FROM stream_positions
|
|
WHERE
|
|
stream_name = ?
|
|
AND instance_name != ALL(?)
|
|
"""
|
|
cur.execute(sql, (self._stream_name, self._writers))
|
|
|
|
sql = """
|
|
SELECT instance_name, stream_id FROM stream_positions
|
|
WHERE stream_name = ?
|
|
"""
|
|
cur.execute(sql, (self._stream_name,))
|
|
|
|
self._current_positions = {
|
|
instance: stream_id * self._return_factor
|
|
for instance, stream_id in cur
|
|
if instance in self._writers
|
|
}
|
|
|
|
# We set the `_persisted_upto_position` to be the minimum of all current
|
|
# positions. If empty we use the max stream ID from the DB table.
|
|
min_stream_id = min(self._current_positions.values(), default=None)
|
|
|
|
if min_stream_id is None:
|
|
# We add a GREATEST here to ensure that the result is always
|
|
# positive. (This can be a problem for e.g. backfill streams where
|
|
# the server has never backfilled).
|
|
sql = """
|
|
SELECT GREATEST(COALESCE(%(agg)s(%(id)s), 1), 1)
|
|
FROM %(table)s
|
|
""" % {
|
|
"id": id_column,
|
|
"table": table,
|
|
"agg": "MAX" if self._positive else "-MIN",
|
|
}
|
|
cur.execute(sql)
|
|
(stream_id,) = cur.fetchone()
|
|
self._persisted_upto_position = stream_id
|
|
else:
|
|
# If we have a min_stream_id then we pull out everything greater
|
|
# than it from the DB so that we can prefill
|
|
# `_known_persisted_positions` and get a more accurate
|
|
# `_persisted_upto_position`.
|
|
#
|
|
# We also check if any of the later rows are from this instance, in
|
|
# which case we use that for this instance's current position. This
|
|
# is to handle the case where we didn't finish persisting to the
|
|
# stream positions table before restart (or the stream position
|
|
# table otherwise got out of date).
|
|
|
|
sql = """
|
|
SELECT %(instance)s, %(id)s FROM %(table)s
|
|
WHERE ? %(cmp)s %(id)s
|
|
""" % {
|
|
"id": id_column,
|
|
"table": table,
|
|
"instance": instance_column,
|
|
"cmp": "<=" if self._positive else ">=",
|
|
}
|
|
cur.execute(sql, (min_stream_id * self._return_factor,))
|
|
|
|
self._persisted_upto_position = min_stream_id
|
|
|
|
with self._lock:
|
|
for (instance, stream_id,) in cur:
|
|
stream_id = self._return_factor * stream_id
|
|
self._add_persisted_position(stream_id)
|
|
|
|
if instance == self._instance_name:
|
|
self._current_positions[instance] = stream_id
|
|
|
|
cur.close()
|
|
|
|
def _load_next_id_txn(self, txn) -> int:
|
|
return self._sequence_gen.get_next_id_txn(txn)
|
|
|
|
def _load_next_mult_id_txn(self, txn, n: int) -> List[int]:
|
|
return self._sequence_gen.get_next_mult_txn(txn, n)
|
|
|
|
def get_next(self):
|
|
"""
|
|
Usage:
|
|
async with stream_id_gen.get_next() as stream_id:
|
|
# ... persist event ...
|
|
"""
|
|
|
|
return _MultiWriterCtxManager(self)
|
|
|
|
def get_next_mult(self, n: int):
|
|
"""
|
|
Usage:
|
|
async with stream_id_gen.get_next_mult(5) as stream_ids:
|
|
# ... persist events ...
|
|
"""
|
|
|
|
return _MultiWriterCtxManager(self, n)
|
|
|
|
def get_next_txn(self, txn: LoggingTransaction):
|
|
"""
|
|
Usage:
|
|
|
|
stream_id = stream_id_gen.get_next(txn)
|
|
# ... persist event ...
|
|
"""
|
|
|
|
next_id = self._load_next_id_txn(txn)
|
|
|
|
with self._lock:
|
|
self._unfinished_ids.add(next_id)
|
|
|
|
txn.call_after(self._mark_id_as_finished, next_id)
|
|
txn.call_on_exception(self._mark_id_as_finished, next_id)
|
|
|
|
# Update the `stream_positions` table with newly updated stream
|
|
# ID (unless self._writers is not set in which case we don't
|
|
# bother, as nothing will read it).
|
|
#
|
|
# We only do this on the success path so that the persisted current
|
|
# position points to a persited row with the correct instance name.
|
|
if self._writers:
|
|
txn.call_after(
|
|
run_as_background_process,
|
|
"MultiWriterIdGenerator._update_table",
|
|
self._db.runInteraction,
|
|
"MultiWriterIdGenerator._update_table",
|
|
self._update_stream_positions_table_txn,
|
|
)
|
|
|
|
return self._return_factor * next_id
|
|
|
|
def _mark_id_as_finished(self, next_id: int):
|
|
"""The ID has finished being processed so we should advance the
|
|
current position if possible.
|
|
"""
|
|
|
|
with self._lock:
|
|
self._unfinished_ids.discard(next_id)
|
|
self._finished_ids.add(next_id)
|
|
|
|
new_cur = None # type: Optional[int]
|
|
|
|
if self._unfinished_ids:
|
|
# If there are unfinished IDs then the new position will be the
|
|
# largest finished ID less than the minimum unfinished ID.
|
|
|
|
finished = set()
|
|
|
|
min_unfinshed = min(self._unfinished_ids)
|
|
for s in self._finished_ids:
|
|
if s < min_unfinshed:
|
|
if new_cur is None or new_cur < s:
|
|
new_cur = s
|
|
else:
|
|
finished.add(s)
|
|
|
|
# We clear these out since they're now all less than the new
|
|
# position.
|
|
self._finished_ids = finished
|
|
else:
|
|
# There are no unfinished IDs so the new position is simply the
|
|
# largest finished one.
|
|
new_cur = max(self._finished_ids)
|
|
|
|
# We clear these out since they're now all less than the new
|
|
# position.
|
|
self._finished_ids.clear()
|
|
|
|
if new_cur:
|
|
curr = self._current_positions.get(self._instance_name, 0)
|
|
self._current_positions[self._instance_name] = max(curr, new_cur)
|
|
|
|
self._add_persisted_position(next_id)
|
|
|
|
def get_current_token(self) -> int:
|
|
"""Returns the maximum stream id such that all stream ids less than or
|
|
equal to it have been successfully persisted.
|
|
"""
|
|
|
|
return self.get_persisted_upto_position()
|
|
|
|
def get_current_token_for_writer(self, instance_name: str) -> int:
|
|
"""Returns the position of the given writer.
|
|
"""
|
|
|
|
# If we don't have an entry for the given instance name, we assume it's a
|
|
# new writer.
|
|
#
|
|
# For new writers we assume their initial position to be the current
|
|
# persisted up to position. This stops Synapse from doing a full table
|
|
# scan when a new writer announces itself over replication.
|
|
with self._lock:
|
|
return self._return_factor * self._current_positions.get(
|
|
instance_name, self._persisted_upto_position
|
|
)
|
|
|
|
def get_positions(self) -> Dict[str, int]:
|
|
"""Get a copy of the current positon map.
|
|
|
|
Note that this won't necessarily include all configured writers if some
|
|
writers haven't written anything yet.
|
|
"""
|
|
|
|
with self._lock:
|
|
return {
|
|
name: self._return_factor * i
|
|
for name, i in self._current_positions.items()
|
|
}
|
|
|
|
def advance(self, instance_name: str, new_id: int):
|
|
"""Advance the postion of the named writer to the given ID, if greater
|
|
than existing entry.
|
|
"""
|
|
|
|
new_id *= self._return_factor
|
|
|
|
with self._lock:
|
|
self._current_positions[instance_name] = max(
|
|
new_id, self._current_positions.get(instance_name, 0)
|
|
)
|
|
|
|
self._add_persisted_position(new_id)
|
|
|
|
def get_persisted_upto_position(self) -> int:
|
|
"""Get the max position where all previous positions have been
|
|
persisted.
|
|
|
|
Note: In the worst case scenario this will be equal to the minimum
|
|
position across writers. This means that the returned position here can
|
|
lag if one writer doesn't write very often.
|
|
"""
|
|
|
|
with self._lock:
|
|
return self._return_factor * self._persisted_upto_position
|
|
|
|
def _add_persisted_position(self, new_id: int):
|
|
"""Record that we have persisted a position.
|
|
|
|
This is used to keep the `_current_positions` up to date.
|
|
"""
|
|
|
|
# We require that the lock is locked by caller
|
|
assert self._lock.locked()
|
|
|
|
heapq.heappush(self._known_persisted_positions, new_id)
|
|
|
|
# If we're a writer and we don't have any active writes we update our
|
|
# current position to the latest position seen. This allows the instance
|
|
# to report a recent position when asked, rather than a potentially old
|
|
# one (if this instance hasn't written anything for a while).
|
|
our_current_position = self._current_positions.get(self._instance_name)
|
|
if our_current_position and not self._unfinished_ids:
|
|
self._current_positions[self._instance_name] = max(
|
|
our_current_position, new_id
|
|
)
|
|
|
|
# We move the current min position up if the minimum current positions
|
|
# of all instances is higher (since by definition all positions less
|
|
# that that have been persisted).
|
|
min_curr = min(self._current_positions.values(), default=0)
|
|
self._persisted_upto_position = max(min_curr, self._persisted_upto_position)
|
|
|
|
# We now iterate through the seen positions, discarding those that are
|
|
# less than the current min positions, and incrementing the min position
|
|
# if its exactly one greater.
|
|
#
|
|
# This is also where we discard items from `_known_persisted_positions`
|
|
# (to ensure the list doesn't infinitely grow).
|
|
while self._known_persisted_positions:
|
|
if self._known_persisted_positions[0] <= self._persisted_upto_position:
|
|
heapq.heappop(self._known_persisted_positions)
|
|
elif (
|
|
self._known_persisted_positions[0] == self._persisted_upto_position + 1
|
|
):
|
|
heapq.heappop(self._known_persisted_positions)
|
|
self._persisted_upto_position += 1
|
|
else:
|
|
# There was a gap in seen positions, so there is nothing more to
|
|
# do.
|
|
break
|
|
|
|
def _update_stream_positions_table_txn(self, txn: Cursor):
|
|
"""Update the `stream_positions` table with newly persisted position.
|
|
"""
|
|
|
|
if not self._writers:
|
|
return
|
|
|
|
# We upsert the value, ensuring on conflict that we always increase the
|
|
# value (or decrease if stream goes backwards).
|
|
sql = """
|
|
INSERT INTO stream_positions (stream_name, instance_name, stream_id)
|
|
VALUES (?, ?, ?)
|
|
ON CONFLICT (stream_name, instance_name)
|
|
DO UPDATE SET
|
|
stream_id = %(agg)s(stream_positions.stream_id, EXCLUDED.stream_id)
|
|
""" % {
|
|
"agg": "GREATEST" if self._positive else "LEAST",
|
|
}
|
|
|
|
pos = (self.get_current_token_for_writer(self._instance_name),)
|
|
txn.execute(sql, (self._stream_name, self._instance_name, pos))
|
|
|
|
|
|
@attr.s(slots=True)
|
|
class _AsyncCtxManagerWrapper:
|
|
"""Helper class to convert a plain context manager to an async one.
|
|
|
|
This is mainly useful if you have a plain context manager but the interface
|
|
requires an async one.
|
|
"""
|
|
|
|
inner = attr.ib()
|
|
|
|
async def __aenter__(self):
|
|
return self.inner.__enter__()
|
|
|
|
async def __aexit__(self, exc_type, exc, tb):
|
|
return self.inner.__exit__(exc_type, exc, tb)
|
|
|
|
|
|
@attr.s(slots=True)
|
|
class _MultiWriterCtxManager:
|
|
"""Async context manager returned by MultiWriterIdGenerator
|
|
"""
|
|
|
|
id_gen = attr.ib(type=MultiWriterIdGenerator)
|
|
multiple_ids = attr.ib(type=Optional[int], default=None)
|
|
stream_ids = attr.ib(type=List[int], factory=list)
|
|
|
|
async def __aenter__(self) -> Union[int, List[int]]:
|
|
# It's safe to run this in autocommit mode as fetching values from a
|
|
# sequence ignores transaction semantics anyway.
|
|
self.stream_ids = await self.id_gen._db.runInteraction(
|
|
"_load_next_mult_id",
|
|
self.id_gen._load_next_mult_id_txn,
|
|
self.multiple_ids or 1,
|
|
db_autocommit=True,
|
|
)
|
|
|
|
with self.id_gen._lock:
|
|
self.id_gen._unfinished_ids.update(self.stream_ids)
|
|
|
|
if self.multiple_ids is None:
|
|
return self.stream_ids[0] * self.id_gen._return_factor
|
|
else:
|
|
return [i * self.id_gen._return_factor for i in self.stream_ids]
|
|
|
|
async def __aexit__(self, exc_type, exc, tb):
|
|
for i in self.stream_ids:
|
|
self.id_gen._mark_id_as_finished(i)
|
|
|
|
if exc_type is not None:
|
|
return False
|
|
|
|
# Update the `stream_positions` table with newly updated stream
|
|
# ID (unless self._writers is not set in which case we don't
|
|
# bother, as nothing will read it).
|
|
#
|
|
# We only do this on the success path so that the persisted current
|
|
# position points to a persisted row with the correct instance name.
|
|
#
|
|
# We do this in autocommit mode as a) the upsert works correctly outside
|
|
# transactions and b) reduces the amount of time the rows are locked
|
|
# for. If we don't do this then we'll often hit serialization errors due
|
|
# to the fact we default to REPEATABLE READ isolation levels.
|
|
if self.id_gen._writers:
|
|
await self.id_gen._db.runInteraction(
|
|
"MultiWriterIdGenerator._update_table",
|
|
self.id_gen._update_stream_positions_table_txn,
|
|
db_autocommit=True,
|
|
)
|
|
|
|
return False
|