diff --git a/changelog.d/16112.misc b/changelog.d/16112.misc
new file mode 100644
index 0000000000..05a58c1348
--- /dev/null
+++ b/changelog.d/16112.misc
@@ -0,0 +1 @@
+Rename pagination and purge locks and add comments to explain why they exist and how they work.
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index a90d99c4d6..f9915e5a3f 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -63,7 +63,7 @@ from synapse.federation.federation_base import (
)
from synapse.federation.persistence import TransactionActions
from synapse.federation.units import Edu, Transaction
-from synapse.handlers.worker_lock import DELETE_ROOM_LOCK_NAME
+from synapse.handlers.worker_lock import NEW_EVENT_DURING_PURGE_LOCK_NAME
from synapse.http.servlet import assert_params_in_dict
from synapse.logging.context import (
make_deferred_yieldable,
@@ -1245,7 +1245,7 @@ class FederationServer(FederationBase):
# while holding the `_INBOUND_EVENT_HANDLING_LOCK_NAME`
# lock.
async with self._worker_lock_handler.acquire_read_write_lock(
- DELETE_ROOM_LOCK_NAME, room_id, write=False
+ NEW_EVENT_DURING_PURGE_LOCK_NAME, room_id, write=False
):
await self._federation_event_handler.on_receive_pdu(
origin, event
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index d485f21e49..a74db1dccf 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -53,7 +53,7 @@ from synapse.events.snapshot import EventContext, UnpersistedEventContextBase
from synapse.events.utils import SerializeEventConfig, maybe_upsert_event_field
from synapse.events.validator import EventValidator
from synapse.handlers.directory import DirectoryHandler
-from synapse.handlers.worker_lock import DELETE_ROOM_LOCK_NAME
+from synapse.handlers.worker_lock import NEW_EVENT_DURING_PURGE_LOCK_NAME
from synapse.logging import opentracing
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.metrics.background_process_metrics import run_as_background_process
@@ -1034,7 +1034,7 @@ class EventCreationHandler:
)
async with self._worker_lock_handler.acquire_read_write_lock(
- DELETE_ROOM_LOCK_NAME, room_id, write=False
+ NEW_EVENT_DURING_PURGE_LOCK_NAME, room_id, write=False
):
return await self._create_and_send_nonmember_event_locked(
requester=requester,
@@ -1978,7 +1978,7 @@ class EventCreationHandler:
for room_id in room_ids:
async with self._worker_lock_handler.acquire_read_write_lock(
- DELETE_ROOM_LOCK_NAME, room_id, write=False
+ NEW_EVENT_DURING_PURGE_LOCK_NAME, room_id, write=False
):
dummy_event_sent = await self._send_dummy_event_for_room(room_id)
diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index da34658470..1be6ebc6d9 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -24,6 +24,7 @@ from synapse.api.errors import SynapseError
from synapse.api.filtering import Filter
from synapse.events.utils import SerializeEventConfig
from synapse.handlers.room import ShutdownRoomResponse
+from synapse.handlers.worker_lock import NEW_EVENT_DURING_PURGE_LOCK_NAME
from synapse.logging.opentracing import trace
from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.rest.admin._base import assert_user_is_admin
@@ -46,9 +47,10 @@ logger = logging.getLogger(__name__)
BACKFILL_BECAUSE_TOO_MANY_GAPS_THRESHOLD = 3
-PURGE_HISTORY_LOCK_NAME = "purge_history_lock"
-
-DELETE_ROOM_LOCK_NAME = "delete_room_lock"
+# This is used to avoid purging a room several time at the same moment,
+# and also paginating during a purge. Pagination can trigger backfill,
+# which would create old events locally, and would potentially clash with the room delete.
+PURGE_PAGINATION_LOCK_NAME = "purge_pagination_lock"
@attr.s(slots=True, auto_attribs=True)
@@ -363,7 +365,7 @@ class PaginationHandler:
self._purges_in_progress_by_room.add(room_id)
try:
async with self._worker_locks.acquire_read_write_lock(
- PURGE_HISTORY_LOCK_NAME, room_id, write=True
+ PURGE_PAGINATION_LOCK_NAME, room_id, write=True
):
await self._storage_controllers.purge_events.purge_history(
room_id, token, delete_local_events
@@ -421,7 +423,10 @@ class PaginationHandler:
force: set true to skip checking for joined users.
"""
async with self._worker_locks.acquire_multi_read_write_lock(
- [(PURGE_HISTORY_LOCK_NAME, room_id), (DELETE_ROOM_LOCK_NAME, room_id)],
+ [
+ (PURGE_PAGINATION_LOCK_NAME, room_id),
+ (NEW_EVENT_DURING_PURGE_LOCK_NAME, room_id),
+ ],
write=True,
):
# first check that we have no users in this room
@@ -483,7 +488,7 @@ class PaginationHandler:
room_token = from_token.room_key
async with self._worker_locks.acquire_read_write_lock(
- PURGE_HISTORY_LOCK_NAME, room_id, write=False
+ PURGE_PAGINATION_LOCK_NAME, room_id, write=False
):
(membership, member_event_id) = (None, None)
if not use_admin_priviledge:
@@ -761,7 +766,7 @@ class PaginationHandler:
self._purges_in_progress_by_room.add(room_id)
try:
async with self._worker_locks.acquire_read_write_lock(
- PURGE_HISTORY_LOCK_NAME, room_id, write=True
+ PURGE_PAGINATION_LOCK_NAME, room_id, write=True
):
self._delete_by_id[delete_id].status = DeleteStatus.STATUS_SHUTTING_DOWN
self._delete_by_id[
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index e3cdf2bc61..1d8d4a72e7 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -39,7 +39,7 @@ from synapse.events import EventBase
from synapse.events.snapshot import EventContext
from synapse.handlers.profile import MAX_AVATAR_URL_LEN, MAX_DISPLAYNAME_LEN
from synapse.handlers.state_deltas import MatchChange, StateDeltasHandler
-from synapse.handlers.worker_lock import DELETE_ROOM_LOCK_NAME
+from synapse.handlers.worker_lock import NEW_EVENT_DURING_PURGE_LOCK_NAME
from synapse.logging import opentracing
from synapse.metrics import event_processing_positions
from synapse.metrics.background_process_metrics import run_as_background_process
@@ -621,7 +621,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
async with self.member_as_limiter.queue(as_id):
async with self.member_linearizer.queue(key):
async with self._worker_lock_handler.acquire_read_write_lock(
- DELETE_ROOM_LOCK_NAME, room_id, write=False
+ NEW_EVENT_DURING_PURGE_LOCK_NAME, room_id, write=False
):
with opentracing.start_active_span("update_membership_locked"):
result = await self.update_membership_locked(
diff --git a/synapse/handlers/worker_lock.py b/synapse/handlers/worker_lock.py
index 72df773a86..58efe7116b 100644
--- a/synapse/handlers/worker_lock.py
+++ b/synapse/handlers/worker_lock.py
@@ -42,7 +42,11 @@ if TYPE_CHECKING:
from synapse.server import HomeServer
-DELETE_ROOM_LOCK_NAME = "delete_room_lock"
+# This lock is used to avoid creating an event while we are purging the room.
+# We take a read lock when creating an event, and a write one when purging a room.
+# This is because it is fine to create several events concurrently, since referenced events
+# will not disappear under our feet as long as we don't delete the room.
+NEW_EVENT_DURING_PURGE_LOCK_NAME = "new_event_during_purge_lock"
class WorkerLocksHandler:
diff --git a/synapse/rest/client/room_upgrade_rest_servlet.py b/synapse/rest/client/room_upgrade_rest_servlet.py
index 4a5d9e13e7..b1f6b5d1b7 100644
--- a/synapse/rest/client/room_upgrade_rest_servlet.py
+++ b/synapse/rest/client/room_upgrade_rest_servlet.py
@@ -17,7 +17,7 @@ from typing import TYPE_CHECKING, Tuple
from synapse.api.errors import Codes, ShadowBanError, SynapseError
from synapse.api.room_versions import KNOWN_ROOM_VERSIONS
-from synapse.handlers.worker_lock import DELETE_ROOM_LOCK_NAME
+from synapse.handlers.worker_lock import NEW_EVENT_DURING_PURGE_LOCK_NAME
from synapse.http.server import HttpServer
from synapse.http.servlet import (
RestServlet,
@@ -81,7 +81,7 @@ class RoomUpgradeRestServlet(RestServlet):
try:
async with self._worker_lock_handler.acquire_read_write_lock(
- DELETE_ROOM_LOCK_NAME, room_id, write=False
+ NEW_EVENT_DURING_PURGE_LOCK_NAME, room_id, write=False
):
new_room_id = await self._room_creation_handler.upgrade_room(
requester, room_id, new_version
diff --git a/synapse/storage/controllers/persist_events.py b/synapse/storage/controllers/persist_events.py
index 35cd1089d6..abd1d149db 100644
--- a/synapse/storage/controllers/persist_events.py
+++ b/synapse/storage/controllers/persist_events.py
@@ -45,7 +45,7 @@ from twisted.internet import defer
from synapse.api.constants import EventTypes, Membership
from synapse.events import EventBase
from synapse.events.snapshot import EventContext
-from synapse.handlers.worker_lock import DELETE_ROOM_LOCK_NAME
+from synapse.handlers.worker_lock import NEW_EVENT_DURING_PURGE_LOCK_NAME
from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
from synapse.logging.opentracing import (
SynapseTags,
@@ -357,7 +357,7 @@ class EventsPersistenceStorageController:
# it. We might already have taken out the lock, but since this is just a
# "read" lock its inherently reentrant.
async with self.hs.get_worker_locks_handler().acquire_read_write_lock(
- DELETE_ROOM_LOCK_NAME, room_id, write=False
+ NEW_EVENT_DURING_PURGE_LOCK_NAME, room_id, write=False
):
if isinstance(task, _PersistEventsTask):
return await self._persist_event_batch(room_id, task)
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