From 40a3583ba14cc32f63154afc9e2c9b1058697f16 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Wed, 19 Jul 2023 12:06:38 +0100 Subject: [PATCH] Fix race in triggers for read/write locks. (#15933) --- changelog.d/15933.misc | 1 + .../04_read_write_locks_triggers.sql.postgres | 51 -------------- .../04_read_write_locks_triggers.sql.sqlite | 47 ------------- .../03_read_write_locks_triggers.sql.postgres | 69 +++++++++++++++++++ .../03_read_write_locks_triggers.sql.sqlite | 65 +++++++++++++++++ 5 files changed, 135 insertions(+), 98 deletions(-) create mode 100644 changelog.d/15933.misc create mode 100644 synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.postgres create mode 100644 synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.sqlite diff --git a/changelog.d/15933.misc b/changelog.d/15933.misc new file mode 100644 index 0000000000..8457994c68 --- /dev/null +++ b/changelog.d/15933.misc @@ -0,0 +1 @@ +Fix bug with read/write lock implementation. This is currently unused so has no observable effects. diff --git a/synapse/storage/schema/main/delta/78/04_read_write_locks_triggers.sql.postgres b/synapse/storage/schema/main/delta/78/04_read_write_locks_triggers.sql.postgres index e1a41be9c9..e1cc3469a4 100644 --- a/synapse/storage/schema/main/delta/78/04_read_write_locks_triggers.sql.postgres +++ b/synapse/storage/schema/main/delta/78/04_read_write_locks_triggers.sql.postgres @@ -99,54 +99,3 @@ CREATE UNIQUE INDEX worker_read_write_locks_write ON worker_read_write_locks (lo -- constraints. ALTER TABLE worker_read_write_locks_mode ADD CONSTRAINT worker_read_write_locks_mode_foreign FOREIGN KEY (lock_name, lock_key, token) REFERENCES worker_read_write_locks(lock_name, lock_key, token) DEFERRABLE INITIALLY DEFERRED; - - --- Add a trigger to UPSERT into `worker_read_write_locks_mode` whenever we try --- and acquire a lock, i.e. insert into `worker_read_write_locks`, -CREATE OR REPLACE FUNCTION upsert_read_write_lock_parent() RETURNS trigger AS $$ -BEGIN - INSERT INTO worker_read_write_locks_mode (lock_name, lock_key, write_lock, token) - VALUES (NEW.lock_name, NEW.lock_key, NEW.write_lock, NEW.token) - ON CONFLICT (lock_name, lock_key) - DO NOTHING; - RETURN NEW; -END -$$ -LANGUAGE plpgsql; - -CREATE TRIGGER upsert_read_write_lock_parent_trigger BEFORE INSERT ON worker_read_write_locks - FOR EACH ROW - EXECUTE PROCEDURE upsert_read_write_lock_parent(); - - --- Ensure that we keep `worker_read_write_locks_mode` up to date whenever a lock --- is released (i.e. a row deleted from `worker_read_write_locks`). Either we --- update the `worker_read_write_locks_mode.token` to match another instance --- that has currently acquired the lock, or we delete the row if nobody has --- currently acquired a lock. -CREATE OR REPLACE FUNCTION delete_read_write_lock_parent() RETURNS trigger AS $$ -DECLARE - new_token TEXT; -BEGIN - SELECT token INTO new_token FROM worker_read_write_locks - WHERE - lock_name = OLD.lock_name - AND lock_key = OLD.lock_key; - - IF NOT FOUND THEN - DELETE FROM worker_read_write_locks_mode - WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key; - ELSE - UPDATE worker_read_write_locks_mode - SET token = new_token - WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key; - END IF; - - RETURN NEW; -END -$$ -LANGUAGE plpgsql; - -CREATE TRIGGER delete_read_write_lock_parent_trigger AFTER DELETE ON worker_read_write_locks - FOR EACH ROW - EXECUTE PROCEDURE delete_read_write_lock_parent(); diff --git a/synapse/storage/schema/main/delta/78/04_read_write_locks_triggers.sql.sqlite b/synapse/storage/schema/main/delta/78/04_read_write_locks_triggers.sql.sqlite index be2dfbbb8a..b15432f576 100644 --- a/synapse/storage/schema/main/delta/78/04_read_write_locks_triggers.sql.sqlite +++ b/synapse/storage/schema/main/delta/78/04_read_write_locks_triggers.sql.sqlite @@ -70,50 +70,3 @@ CREATE TABLE worker_read_write_locks ( CREATE UNIQUE INDEX worker_read_write_locks_key ON worker_read_write_locks (lock_name, lock_key, token); -- Ensures that only one instance can acquire a lock in write mode at a time. CREATE UNIQUE INDEX worker_read_write_locks_write ON worker_read_write_locks (lock_name, lock_key) WHERE write_lock; - - --- Add a trigger to UPSERT into `worker_read_write_locks_mode` whenever we try --- and acquire a lock, i.e. insert into `worker_read_write_locks`, -CREATE TRIGGER IF NOT EXISTS upsert_read_write_lock_parent_trigger -BEFORE INSERT ON worker_read_write_locks -FOR EACH ROW -BEGIN - -- First ensure that `worker_read_write_locks_mode` doesn't have stale - -- entries in it, as on SQLite we don't have the foreign key constraint to - -- enforce this. - DELETE FROM worker_read_write_locks_mode - WHERE lock_name = NEW.lock_name AND lock_key = NEW.lock_key - AND NOT EXISTS ( - SELECT 1 FROM worker_read_write_locks - WHERE lock_name = NEW.lock_name AND lock_key = NEW.lock_key - ); - - INSERT INTO worker_read_write_locks_mode (lock_name, lock_key, write_lock, token) - VALUES (NEW.lock_name, NEW.lock_key, NEW.write_lock, NEW.token) - ON CONFLICT (lock_name, lock_key) - DO NOTHING; -END; - --- Ensure that we keep `worker_read_write_locks_mode` up to date whenever a lock --- is released (i.e. a row deleted from `worker_read_write_locks`). Either we --- update the `worker_read_write_locks_mode.token` to match another instance --- that has currently acquired the lock, or we delete the row if nobody has --- currently acquired a lock. -CREATE TRIGGER IF NOT EXISTS delete_read_write_lock_parent_trigger -AFTER DELETE ON worker_read_write_locks -FOR EACH ROW -BEGIN - DELETE FROM worker_read_write_locks_mode - WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key - AND NOT EXISTS ( - SELECT 1 FROM worker_read_write_locks - WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key - ); - - UPDATE worker_read_write_locks_mode - SET token = ( - SELECT token FROM worker_read_write_locks - WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key - ) - WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key; -END; diff --git a/synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.postgres b/synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.postgres new file mode 100644 index 0000000000..ea3496ef2d --- /dev/null +++ b/synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.postgres @@ -0,0 +1,69 @@ +/* Copyright 2023 The Matrix.org Foundation C.I.C + * + * 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. + */ + +-- Fix up the triggers that were in `78/04_read_write_locks_triggers.sql` + +-- Add a trigger to UPSERT into `worker_read_write_locks_mode` whenever we try +-- and acquire a lock, i.e. insert into `worker_read_write_locks`, +CREATE OR REPLACE FUNCTION upsert_read_write_lock_parent() RETURNS trigger AS $$ +BEGIN + INSERT INTO worker_read_write_locks_mode (lock_name, lock_key, write_lock, token) + VALUES (NEW.lock_name, NEW.lock_key, NEW.write_lock, NEW.token) + ON CONFLICT (lock_name, lock_key) + DO UPDATE SET write_lock = NEW.write_lock, token = NEW.token; + RETURN NEW; +END +$$ +LANGUAGE plpgsql; + +DROP TRIGGER IF EXISTS upsert_read_write_lock_parent_trigger ON worker_read_write_locks; +CREATE TRIGGER upsert_read_write_lock_parent_trigger BEFORE INSERT ON worker_read_write_locks + FOR EACH ROW + EXECUTE PROCEDURE upsert_read_write_lock_parent(); + + +-- Ensure that we keep `worker_read_write_locks_mode` up to date whenever a lock +-- is released (i.e. a row deleted from `worker_read_write_locks`). Either we +-- update the `worker_read_write_locks_mode.token` to match another instance +-- that has currently acquired the lock, or we delete the row if nobody has +-- currently acquired a lock. +CREATE OR REPLACE FUNCTION delete_read_write_lock_parent() RETURNS trigger AS $$ +DECLARE + new_token TEXT; +BEGIN + SELECT token INTO new_token FROM worker_read_write_locks + WHERE + lock_name = OLD.lock_name + AND lock_key = OLD.lock_key + LIMIT 1 FOR UPDATE; + + IF NOT FOUND THEN + DELETE FROM worker_read_write_locks_mode + WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key AND token = OLD.token; + ELSE + UPDATE worker_read_write_locks_mode + SET token = new_token + WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key; + END IF; + + RETURN NEW; +END +$$ +LANGUAGE plpgsql; + +DROP TRIGGER IF EXISTS delete_read_write_lock_parent_trigger ON worker_read_write_locks; +CREATE TRIGGER delete_read_write_lock_parent_trigger AFTER DELETE ON worker_read_write_locks + FOR EACH ROW + EXECUTE PROCEDURE delete_read_write_lock_parent(); diff --git a/synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.sqlite b/synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.sqlite new file mode 100644 index 0000000000..acb1a77c80 --- /dev/null +++ b/synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.sqlite @@ -0,0 +1,65 @@ +/* Copyright 2023 The Matrix.org Foundation C.I.C + * + * 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. + */ + +-- Fix up the triggers that were in `78/04_read_write_locks_triggers.sql` + +-- Add a trigger to UPSERT into `worker_read_write_locks_mode` whenever we try +-- and acquire a lock, i.e. insert into `worker_read_write_locks`, +DROP TRIGGER IF EXISTS upsert_read_write_lock_parent_trigger; +CREATE TRIGGER IF NOT EXISTS upsert_read_write_lock_parent_trigger +BEFORE INSERT ON worker_read_write_locks +FOR EACH ROW +BEGIN + -- First ensure that `worker_read_write_locks_mode` doesn't have stale + -- entries in it, as on SQLite we don't have the foreign key constraint to + -- enforce this. + DELETE FROM worker_read_write_locks_mode + WHERE lock_name = NEW.lock_name AND lock_key = NEW.lock_key + AND NOT EXISTS ( + SELECT 1 FROM worker_read_write_locks + WHERE lock_name = NEW.lock_name AND lock_key = NEW.lock_key + ); + + INSERT INTO worker_read_write_locks_mode (lock_name, lock_key, write_lock, token) + VALUES (NEW.lock_name, NEW.lock_key, NEW.write_lock, NEW.token) + ON CONFLICT (lock_name, lock_key) + DO UPDATE SET write_lock = NEW.write_lock, token = NEW.token; +END; + +-- Ensure that we keep `worker_read_write_locks_mode` up to date whenever a lock +-- is released (i.e. a row deleted from `worker_read_write_locks`). Either we +-- update the `worker_read_write_locks_mode.token` to match another instance +-- that has currently acquired the lock, or we delete the row if nobody has +-- currently acquired a lock. +DROP TRIGGER IF EXISTS delete_read_write_lock_parent_trigger; +CREATE TRIGGER IF NOT EXISTS delete_read_write_lock_parent_trigger +AFTER DELETE ON worker_read_write_locks +FOR EACH ROW +BEGIN + DELETE FROM worker_read_write_locks_mode + WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key + AND token = OLD.token + AND NOT EXISTS ( + SELECT 1 FROM worker_read_write_locks + WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key + ); + + UPDATE worker_read_write_locks_mode + SET token = ( + SELECT token FROM worker_read_write_locks + WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key + ) + WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key; +END;