Fix database performance of read/write worker locks (#16061)

We were seeing serialization errors when taking out multiple read locks.

The transactions were retried, so isn't causing any failures.

Introduced in #15782.
This commit is contained in:
Erik Johnston 2023-08-17 14:07:57 +01:00 committed by GitHub
parent 0377cb4fab
commit eb0dbab15b
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3 changed files with 40 additions and 55 deletions

1
changelog.d/16061.misc Normal file
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@ -0,0 +1 @@
Fix database performance of read/write worker locks.

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@ -26,7 +26,6 @@ from synapse.storage.database import (
LoggingDatabaseConnection,
LoggingTransaction,
)
from synapse.storage.engines import PostgresEngine
from synapse.util import Clock
from synapse.util.stringutils import random_string
@ -96,6 +95,10 @@ class LockStore(SQLBaseStore):
self._acquiring_locks: Set[Tuple[str, str]] = set()
self._clock.looping_call(
self._reap_stale_read_write_locks, _LOCK_TIMEOUT_MS / 10.0
)
@wrap_as_background_process("LockStore._on_shutdown")
async def _on_shutdown(self) -> None:
"""Called when the server is shutting down"""
@ -216,6 +219,7 @@ class LockStore(SQLBaseStore):
lock_name,
lock_key,
write,
db_autocommit=True,
)
except self.database_engine.module.IntegrityError:
return None
@ -233,61 +237,22 @@ class LockStore(SQLBaseStore):
# `worker_read_write_locks` and seeing if that fails any
# constraints. If it doesn't then we have acquired the lock,
# otherwise we haven't.
#
# Before that though we clear the table of any stale locks.
now = self._clock.time_msec()
token = random_string(6)
delete_sql = """
DELETE FROM worker_read_write_locks
WHERE last_renewed_ts < ? AND lock_name = ? AND lock_key = ?;
"""
insert_sql = """
INSERT INTO worker_read_write_locks (lock_name, lock_key, write_lock, instance_name, token, last_renewed_ts)
VALUES (?, ?, ?, ?, ?, ?)
"""
if isinstance(self.database_engine, PostgresEngine):
# For Postgres we can send these queries at the same time.
txn.execute(
delete_sql + ";" + insert_sql,
(
# DELETE args
now - _LOCK_TIMEOUT_MS,
lock_name,
lock_key,
# UPSERT args
lock_name,
lock_key,
write,
self._instance_name,
token,
now,
),
)
else:
# For SQLite these need to be two queries.
txn.execute(
delete_sql,
(
now - _LOCK_TIMEOUT_MS,
lock_name,
lock_key,
),
)
txn.execute(
insert_sql,
(
lock_name,
lock_key,
write,
self._instance_name,
token,
now,
),
)
self.db_pool.simple_insert_txn(
txn,
table="worker_read_write_locks",
values={
"lock_name": lock_name,
"lock_key": lock_key,
"write_lock": write,
"instance_name": self._instance_name,
"token": token,
"last_renewed_ts": now,
},
)
lock = Lock(
self._reactor,
@ -351,6 +316,24 @@ class LockStore(SQLBaseStore):
return locks
@wrap_as_background_process("_reap_stale_read_write_locks")
async def _reap_stale_read_write_locks(self) -> None:
delete_sql = """
DELETE FROM worker_read_write_locks
WHERE last_renewed_ts < ?
"""
def reap_stale_read_write_locks_txn(txn: LoggingTransaction) -> None:
txn.execute(delete_sql, (self._clock.time_msec() - _LOCK_TIMEOUT_MS,))
if txn.rowcount:
logger.info("Reaped %d stale locks", txn.rowcount)
await self.db_pool.runInteraction(
"_reap_stale_read_write_locks",
reap_stale_read_write_locks_txn,
db_autocommit=True,
)
class Lock:
"""An async context manager that manages an acquired lock, ensuring it is

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@ -12,13 +12,14 @@
# See the License for the specific language governing permissions and
# limitations under the License.
from twisted.internet import defer, reactor
from twisted.internet.base import ReactorBase
from twisted.internet.defer import Deferred
from twisted.test.proto_helpers import MemoryReactor
from synapse.server import HomeServer
from synapse.storage.databases.main.lock import _LOCK_TIMEOUT_MS
from synapse.storage.databases.main.lock import _LOCK_TIMEOUT_MS, _RENEWAL_INTERVAL_MS
from synapse.util import Clock
from tests import unittest
@ -380,8 +381,8 @@ class ReadWriteLockTestCase(unittest.HomeserverTestCase):
self.get_success(lock.__aenter__())
# Wait for ages with the lock, we should not be able to get the lock.
self.reactor.advance(5 * _LOCK_TIMEOUT_MS / 1000)
self.pump()
for _ in range(0, 10):
self.reactor.advance((_RENEWAL_INTERVAL_MS / 1000))
lock2 = self.get_success(
self.store.try_acquire_read_write_lock("name", "key", write=True)