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f112cfe5bb
On startup `MultiWriteIdGenerator` fetches the maximum stream ID for each instance from the table and uses that as its initial "current position" for each writer. This is problematic as a) it involves either a scan of events table or an index (neither of which is ideal), and b) if rows are being persisted out of order elsewhere while the process restarts then using the maximum stream ID is not correct. This could theoretically lead to race conditions where e.g. events that are persisted out of order are not sent down sync streams. We fix this by creating a new table that tracks the current positions of each writer to the stream, and update it each time we finish persisting a new entry. This is a relatively small overhead when persisting events. However for the cache invalidation stream this is a much bigger relative overhead, so instead we note that for invalidation we don't actually care about reliability over restarts (as there's no caches to invalidate) and simply don't bother reading and writing to the new table in that particular case.
541 lines
20 KiB
Python
541 lines
20 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2020 The Matrix.org Foundation C.I.C.
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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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from synapse.storage.database import DatabasePool
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from synapse.storage.util.id_generators import MultiWriterIdGenerator
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from tests.unittest import HomeserverTestCase
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from tests.utils import USE_POSTGRES_FOR_TESTS
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class MultiWriterIdGeneratorTestCase(HomeserverTestCase):
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if not USE_POSTGRES_FOR_TESTS:
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skip = "Requires Postgres"
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def prepare(self, reactor, clock, hs):
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self.store = hs.get_datastore()
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self.db_pool = self.store.db_pool # type: DatabasePool
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self.get_success(self.db_pool.runInteraction("_setup_db", self._setup_db))
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def _setup_db(self, txn):
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txn.execute("CREATE SEQUENCE foobar_seq")
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txn.execute(
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"""
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CREATE TABLE foobar (
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stream_id BIGINT NOT NULL,
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instance_name TEXT NOT NULL,
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data TEXT
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);
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"""
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)
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def _create_id_generator(
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self, instance_name="master", writers=["master"]
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) -> MultiWriterIdGenerator:
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def _create(conn):
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return MultiWriterIdGenerator(
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conn,
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self.db_pool,
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stream_name="test_stream",
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instance_name=instance_name,
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table="foobar",
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instance_column="instance_name",
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id_column="stream_id",
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sequence_name="foobar_seq",
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writers=writers,
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)
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return self.get_success(self.db_pool.runWithConnection(_create))
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def _insert_rows(self, instance_name: str, number: int):
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"""Insert N rows as the given instance, inserting with stream IDs pulled
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from the postgres sequence.
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"""
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def _insert(txn):
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for _ in range(number):
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txn.execute(
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"INSERT INTO foobar VALUES (nextval('foobar_seq'), ?)",
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(instance_name,),
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)
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txn.execute(
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"""
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INSERT INTO stream_positions VALUES ('test_stream', ?, lastval())
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ON CONFLICT (stream_name, instance_name) DO UPDATE SET stream_id = lastval()
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""",
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(instance_name,),
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)
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self.get_success(self.db_pool.runInteraction("_insert_rows", _insert))
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def _insert_row_with_id(self, instance_name: str, stream_id: int):
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"""Insert one row as the given instance with given stream_id, updating
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the postgres sequence position to match.
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"""
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def _insert(txn):
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txn.execute(
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"INSERT INTO foobar VALUES (?, ?)", (stream_id, instance_name,),
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)
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txn.execute("SELECT setval('foobar_seq', ?)", (stream_id,))
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txn.execute(
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"""
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INSERT INTO stream_positions VALUES ('test_stream', ?, ?)
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ON CONFLICT (stream_name, instance_name) DO UPDATE SET stream_id = ?
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""",
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(instance_name, stream_id, stream_id),
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)
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self.get_success(self.db_pool.runInteraction("_insert_row_with_id", _insert))
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def test_empty(self):
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"""Test an ID generator against an empty database gives sensible
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current positions.
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"""
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id_gen = self._create_id_generator()
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# The table is empty so we expect an empty map for positions
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self.assertEqual(id_gen.get_positions(), {})
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def test_single_instance(self):
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"""Test that reads and writes from a single process are handled
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correctly.
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"""
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# Prefill table with 7 rows written by 'master'
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self._insert_rows("master", 7)
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id_gen = self._create_id_generator()
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self.assertEqual(id_gen.get_positions(), {"master": 7})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 7)
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# Try allocating a new ID gen and check that we only see position
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# advanced after we leave the context manager.
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async def _get_next_async():
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async with id_gen.get_next() as stream_id:
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self.assertEqual(stream_id, 8)
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self.assertEqual(id_gen.get_positions(), {"master": 7})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 7)
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self.get_success(_get_next_async())
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self.assertEqual(id_gen.get_positions(), {"master": 8})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 8)
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def test_out_of_order_finish(self):
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"""Test that IDs persisted out of order are correctly handled
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"""
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# Prefill table with 7 rows written by 'master'
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self._insert_rows("master", 7)
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id_gen = self._create_id_generator()
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self.assertEqual(id_gen.get_positions(), {"master": 7})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 7)
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ctx1 = self.get_success(id_gen.get_next())
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ctx2 = self.get_success(id_gen.get_next())
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ctx3 = self.get_success(id_gen.get_next())
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ctx4 = self.get_success(id_gen.get_next())
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s1 = self.get_success(ctx1.__aenter__())
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s2 = self.get_success(ctx2.__aenter__())
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s3 = self.get_success(ctx3.__aenter__())
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s4 = self.get_success(ctx4.__aenter__())
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self.assertEqual(s1, 8)
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self.assertEqual(s2, 9)
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self.assertEqual(s3, 10)
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self.assertEqual(s4, 11)
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self.assertEqual(id_gen.get_positions(), {"master": 7})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 7)
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self.get_success(ctx2.__aexit__(None, None, None))
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self.assertEqual(id_gen.get_positions(), {"master": 7})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 7)
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self.get_success(ctx1.__aexit__(None, None, None))
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self.assertEqual(id_gen.get_positions(), {"master": 9})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 9)
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self.get_success(ctx4.__aexit__(None, None, None))
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self.assertEqual(id_gen.get_positions(), {"master": 9})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 9)
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self.get_success(ctx3.__aexit__(None, None, None))
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self.assertEqual(id_gen.get_positions(), {"master": 11})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 11)
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def test_multi_instance(self):
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"""Test that reads and writes from multiple processes are handled
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correctly.
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"""
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self._insert_rows("first", 3)
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self._insert_rows("second", 4)
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first_id_gen = self._create_id_generator("first", writers=["first", "second"])
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second_id_gen = self._create_id_generator("second", writers=["first", "second"])
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self.assertEqual(first_id_gen.get_positions(), {"first": 3, "second": 7})
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self.assertEqual(first_id_gen.get_current_token_for_writer("first"), 3)
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self.assertEqual(first_id_gen.get_current_token_for_writer("second"), 7)
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# Try allocating a new ID gen and check that we only see position
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# advanced after we leave the context manager.
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async def _get_next_async():
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async with first_id_gen.get_next() as stream_id:
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self.assertEqual(stream_id, 8)
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self.assertEqual(
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first_id_gen.get_positions(), {"first": 3, "second": 7}
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)
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self.get_success(_get_next_async())
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self.assertEqual(first_id_gen.get_positions(), {"first": 8, "second": 7})
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# However the ID gen on the second instance won't have seen the update
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self.assertEqual(second_id_gen.get_positions(), {"first": 3, "second": 7})
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# ... but calling `get_next` on the second instance should give a unique
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# stream ID
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async def _get_next_async():
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async with second_id_gen.get_next() as stream_id:
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self.assertEqual(stream_id, 9)
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self.assertEqual(
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second_id_gen.get_positions(), {"first": 3, "second": 7}
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)
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self.get_success(_get_next_async())
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self.assertEqual(second_id_gen.get_positions(), {"first": 3, "second": 9})
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# If the second ID gen gets told about the first, it correctly updates
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second_id_gen.advance("first", 8)
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self.assertEqual(second_id_gen.get_positions(), {"first": 8, "second": 9})
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def test_get_next_txn(self):
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"""Test that the `get_next_txn` function works correctly.
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"""
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# Prefill table with 7 rows written by 'master'
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self._insert_rows("master", 7)
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id_gen = self._create_id_generator()
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self.assertEqual(id_gen.get_positions(), {"master": 7})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 7)
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# Try allocating a new ID gen and check that we only see position
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# advanced after we leave the context manager.
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def _get_next_txn(txn):
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stream_id = id_gen.get_next_txn(txn)
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self.assertEqual(stream_id, 8)
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self.assertEqual(id_gen.get_positions(), {"master": 7})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 7)
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self.get_success(self.db_pool.runInteraction("test", _get_next_txn))
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self.assertEqual(id_gen.get_positions(), {"master": 8})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 8)
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def test_get_persisted_upto_position(self):
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"""Test that `get_persisted_upto_position` correctly tracks updates to
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positions.
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"""
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# The following tests are a bit cheeky in that we notify about new
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# positions via `advance` without *actually* advancing the postgres
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# sequence.
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self._insert_row_with_id("first", 3)
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self._insert_row_with_id("second", 5)
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id_gen = self._create_id_generator("first", writers=["first", "second"])
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self.assertEqual(id_gen.get_positions(), {"first": 3, "second": 5})
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# Min is 3 and there is a gap between 5, so we expect it to be 3.
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self.assertEqual(id_gen.get_persisted_upto_position(), 3)
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# We advance "first" straight to 6. Min is now 5 but there is no gap so
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# we expect it to be 6
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id_gen.advance("first", 6)
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self.assertEqual(id_gen.get_persisted_upto_position(), 6)
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# No gap, so we expect 7.
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id_gen.advance("second", 7)
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self.assertEqual(id_gen.get_persisted_upto_position(), 7)
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# We haven't seen 8 yet, so we expect 7 still.
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id_gen.advance("second", 9)
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self.assertEqual(id_gen.get_persisted_upto_position(), 7)
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# Now that we've seen 7, 8 and 9 we can got straight to 9.
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id_gen.advance("first", 8)
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self.assertEqual(id_gen.get_persisted_upto_position(), 9)
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# Jump forward with gaps. The minimum is 11, even though we haven't seen
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# 10 we know that everything before 11 must be persisted.
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id_gen.advance("first", 11)
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id_gen.advance("second", 15)
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self.assertEqual(id_gen.get_persisted_upto_position(), 11)
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def test_get_persisted_upto_position_get_next(self):
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"""Test that `get_persisted_upto_position` correctly tracks updates to
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positions when `get_next` is called.
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"""
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self._insert_row_with_id("first", 3)
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self._insert_row_with_id("second", 5)
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id_gen = self._create_id_generator("first", writers=["first", "second"])
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self.assertEqual(id_gen.get_positions(), {"first": 3, "second": 5})
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self.assertEqual(id_gen.get_persisted_upto_position(), 3)
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async def _get_next_async():
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async with id_gen.get_next() as stream_id:
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self.assertEqual(stream_id, 6)
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self.assertEqual(id_gen.get_persisted_upto_position(), 3)
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self.get_success(_get_next_async())
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self.assertEqual(id_gen.get_persisted_upto_position(), 6)
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# We assume that so long as `get_next` does correctly advance the
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# `persisted_upto_position` in this case, then it will be correct in the
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# other cases that are tested above (since they'll hit the same code).
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def test_restart_during_out_of_order_persistence(self):
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"""Test that restarting a process while another process is writing out
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of order updates are handled correctly.
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"""
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# Prefill table with 7 rows written by 'master'
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self._insert_rows("master", 7)
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id_gen = self._create_id_generator()
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self.assertEqual(id_gen.get_positions(), {"master": 7})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 7)
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# Persist two rows at once
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ctx1 = self.get_success(id_gen.get_next())
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ctx2 = self.get_success(id_gen.get_next())
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s1 = self.get_success(ctx1.__aenter__())
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s2 = self.get_success(ctx2.__aenter__())
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self.assertEqual(s1, 8)
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self.assertEqual(s2, 9)
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self.assertEqual(id_gen.get_positions(), {"master": 7})
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self.assertEqual(id_gen.get_current_token_for_writer("master"), 7)
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# We finish persisting the second row before restart
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self.get_success(ctx2.__aexit__(None, None, None))
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# We simulate a restart of another worker by just creating a new ID gen.
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id_gen_worker = self._create_id_generator("worker")
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# Restarted worker should not see the second persisted row
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self.assertEqual(id_gen_worker.get_positions(), {"master": 7})
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self.assertEqual(id_gen_worker.get_current_token_for_writer("master"), 7)
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# Now if we persist the first row then both instances should jump ahead
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# correctly.
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self.get_success(ctx1.__aexit__(None, None, None))
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self.assertEqual(id_gen.get_positions(), {"master": 9})
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id_gen_worker.advance("master", 9)
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self.assertEqual(id_gen_worker.get_positions(), {"master": 9})
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def test_writer_config_change(self):
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"""Test that changing the writer config correctly works.
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"""
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self._insert_row_with_id("first", 3)
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self._insert_row_with_id("second", 5)
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# Initial config has two writers
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id_gen = self._create_id_generator("first", writers=["first", "second"])
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self.assertEqual(id_gen.get_persisted_upto_position(), 3)
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# New config removes one of the configs. Note that if the writer is
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# removed from config we assume that it has been shut down and has
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# finished persisting, hence why the persisted upto position is 5.
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id_gen_2 = self._create_id_generator("second", writers=["second"])
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self.assertEqual(id_gen_2.get_persisted_upto_position(), 5)
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# This config points to a single, previously unused writer.
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id_gen_3 = self._create_id_generator("third", writers=["third"])
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self.assertEqual(id_gen_3.get_persisted_upto_position(), 5)
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# Check that we get a sane next stream ID with this new config.
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async def _get_next_async():
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async with id_gen_3.get_next() as stream_id:
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self.assertEqual(stream_id, 6)
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self.get_success(_get_next_async())
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self.assertEqual(id_gen_3.get_persisted_upto_position(), 6)
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class BackwardsMultiWriterIdGeneratorTestCase(HomeserverTestCase):
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"""Tests MultiWriterIdGenerator that produce *negative* stream IDs.
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"""
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if not USE_POSTGRES_FOR_TESTS:
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skip = "Requires Postgres"
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def prepare(self, reactor, clock, hs):
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self.store = hs.get_datastore()
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self.db_pool = self.store.db_pool # type: DatabasePool
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self.get_success(self.db_pool.runInteraction("_setup_db", self._setup_db))
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def _setup_db(self, txn):
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txn.execute("CREATE SEQUENCE foobar_seq")
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txn.execute(
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"""
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CREATE TABLE foobar (
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stream_id BIGINT NOT NULL,
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instance_name TEXT NOT NULL,
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data TEXT
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);
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"""
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)
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|
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def _create_id_generator(
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self, instance_name="master", writers=["master"]
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) -> MultiWriterIdGenerator:
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def _create(conn):
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return MultiWriterIdGenerator(
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conn,
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self.db_pool,
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stream_name="test_stream",
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instance_name=instance_name,
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table="foobar",
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instance_column="instance_name",
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id_column="stream_id",
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sequence_name="foobar_seq",
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writers=writers,
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positive=False,
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)
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return self.get_success(self.db_pool.runWithConnection(_create))
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def _insert_row(self, instance_name: str, stream_id: int):
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"""Insert one row as the given instance with given stream_id.
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"""
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def _insert(txn):
|
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txn.execute(
|
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"INSERT INTO foobar VALUES (?, ?)", (stream_id, instance_name,),
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)
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txn.execute(
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"""
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INSERT INTO stream_positions VALUES ('test_stream', ?, ?)
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ON CONFLICT (stream_name, instance_name) DO UPDATE SET stream_id = ?
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""",
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(instance_name, -stream_id, -stream_id),
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)
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self.get_success(self.db_pool.runInteraction("_insert_row", _insert))
|
|
|
|
def test_single_instance(self):
|
|
"""Test that reads and writes from a single process are handled
|
|
correctly.
|
|
"""
|
|
id_gen = self._create_id_generator()
|
|
|
|
async def _get_next_async():
|
|
async with id_gen.get_next() as stream_id:
|
|
self._insert_row("master", stream_id)
|
|
|
|
self.get_success(_get_next_async())
|
|
|
|
self.assertEqual(id_gen.get_positions(), {"master": -1})
|
|
self.assertEqual(id_gen.get_current_token_for_writer("master"), -1)
|
|
self.assertEqual(id_gen.get_persisted_upto_position(), -1)
|
|
|
|
async def _get_next_async2():
|
|
async with id_gen.get_next_mult(3) as stream_ids:
|
|
for stream_id in stream_ids:
|
|
self._insert_row("master", stream_id)
|
|
|
|
self.get_success(_get_next_async2())
|
|
|
|
self.assertEqual(id_gen.get_positions(), {"master": -4})
|
|
self.assertEqual(id_gen.get_current_token_for_writer("master"), -4)
|
|
self.assertEqual(id_gen.get_persisted_upto_position(), -4)
|
|
|
|
# Test loading from DB by creating a second ID gen
|
|
second_id_gen = self._create_id_generator()
|
|
|
|
self.assertEqual(second_id_gen.get_positions(), {"master": -4})
|
|
self.assertEqual(second_id_gen.get_current_token_for_writer("master"), -4)
|
|
self.assertEqual(second_id_gen.get_persisted_upto_position(), -4)
|
|
|
|
def test_multiple_instance(self):
|
|
"""Tests that having multiple instances that get advanced over
|
|
federation works corretly.
|
|
"""
|
|
id_gen_1 = self._create_id_generator("first", writers=["first", "second"])
|
|
id_gen_2 = self._create_id_generator("second", writers=["first", "second"])
|
|
|
|
async def _get_next_async():
|
|
async with id_gen_1.get_next() as stream_id:
|
|
self._insert_row("first", stream_id)
|
|
id_gen_2.advance("first", stream_id)
|
|
|
|
self.get_success(_get_next_async())
|
|
|
|
self.assertEqual(id_gen_1.get_positions(), {"first": -1})
|
|
self.assertEqual(id_gen_2.get_positions(), {"first": -1})
|
|
self.assertEqual(id_gen_1.get_persisted_upto_position(), -1)
|
|
self.assertEqual(id_gen_2.get_persisted_upto_position(), -1)
|
|
|
|
async def _get_next_async2():
|
|
async with id_gen_2.get_next() as stream_id:
|
|
self._insert_row("second", stream_id)
|
|
id_gen_1.advance("second", stream_id)
|
|
|
|
self.get_success(_get_next_async2())
|
|
|
|
self.assertEqual(id_gen_1.get_positions(), {"first": -1, "second": -2})
|
|
self.assertEqual(id_gen_2.get_positions(), {"first": -1, "second": -2})
|
|
self.assertEqual(id_gen_1.get_persisted_upto_position(), -2)
|
|
self.assertEqual(id_gen_2.get_persisted_upto_position(), -2)
|