Bump DB version to 79 since synapse v1.88 was already there (#15998)

changelog.d/15998.bugfix

@@ -0,0 +1 @@
+Internal changelog to be removed.

synapse/storage/schema/__init__.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-SCHEMA_VERSION = 78  # remember to update the list below when updating
+SCHEMA_VERSION = 79  # remember to update the list below when updating
 """Represents the expectations made by the codebase about the database schema
 
 This should be incremented whenever the codebase changes its requirements on the
@@ -106,6 +106,10 @@ Changes in SCHEMA_VERSION = 77
 
 Changes in SCHEMA_VERSION = 78
     - Validate check (full_user_id IS NOT NULL) on tables profiles and user_filters
+
+Changes in SCHEMA_VERSION = 79
+    - Add tables to handle in DB read-write locks.
+    - Add some mitigations for a painful race between foreground and background updates, cf #15677.
 """
 
 

synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.postgres

@@ -44,7 +44,7 @@
 
 -- A table to track whether a lock is currently acquired, and if so whether its
 -- in read or write mode.
-CREATE TABLE worker_read_write_locks_mode (
+CREATE TABLE IF NOT EXISTS worker_read_write_locks_mode (
     lock_name TEXT NOT NULL,
     lock_key TEXT NOT NULL,
     -- Whether this lock is in read (false) or write (true) mode
@@ -55,14 +55,14 @@ CREATE TABLE worker_read_write_locks_mode (
 );
 
 -- Ensure that we can only have one row per lock
-CREATE UNIQUE INDEX worker_read_write_locks_mode_key ON worker_read_write_locks_mode (lock_name, lock_key);
+CREATE UNIQUE INDEX IF NOT EXISTS worker_read_write_locks_mode_key ON worker_read_write_locks_mode (lock_name, lock_key);
 -- We need this (redundant) constraint so that we can have a foreign key
 -- constraint against this table.
-CREATE UNIQUE INDEX worker_read_write_locks_mode_type ON worker_read_write_locks_mode (lock_name, lock_key, write_lock);
+CREATE UNIQUE INDEX IF NOT EXISTS worker_read_write_locks_mode_type ON worker_read_write_locks_mode (lock_name, lock_key, write_lock);
 
 
 -- A table to track who has currently acquired a given lock.
-CREATE TABLE worker_read_write_locks (
+CREATE TABLE IF NOT EXISTS worker_read_write_locks (
     lock_name TEXT NOT NULL,
     lock_key TEXT NOT NULL,
     -- We write the instance name to ease manual debugging, we don't ever read
@@ -84,9 +84,9 @@ CREATE TABLE worker_read_write_locks (
     FOREIGN KEY (lock_name, lock_key, write_lock) REFERENCES worker_read_write_locks_mode (lock_name, lock_key, write_lock)
 );
 
-CREATE UNIQUE INDEX worker_read_write_locks_key ON worker_read_write_locks (lock_name, lock_key, token);
+CREATE UNIQUE INDEX IF NOT EXISTS 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;
+CREATE UNIQUE INDEX IF NOT EXISTS worker_read_write_locks_write ON worker_read_write_locks (lock_name, lock_key) WHERE write_lock;
 
 
 -- Add a foreign key constraint to ensure that if a lock is in
@@ -97,5 +97,6 @@ CREATE UNIQUE INDEX worker_read_write_locks_write ON worker_read_write_locks (lo
 -- We only add to PostgreSQL as SQLite does not support adding constraints
 -- after table creation, and so doesn't support "circular" foreign key
 -- constraints.
+ALTER TABLE worker_read_write_locks_mode DROP CONSTRAINT IF EXISTS worker_read_write_locks_mode_foreign;
 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;

synapse/storage/schema/main/delta/79/03_read_write_locks_triggers.sql.sqlite

@@ -22,7 +22,7 @@
 
 -- A table to track whether a lock is currently acquired, and if so whether its
 -- in read or write mode.
-CREATE TABLE worker_read_write_locks_mode (
+CREATE TABLE IF NOT EXISTS worker_read_write_locks_mode (
     lock_name TEXT NOT NULL,
     lock_key TEXT NOT NULL,
     -- Whether this lock is in read (false) or write (true) mode
@@ -38,14 +38,14 @@ CREATE TABLE worker_read_write_locks_mode (
 );
 
 -- Ensure that we can only have one row per lock
-CREATE UNIQUE INDEX worker_read_write_locks_mode_key ON worker_read_write_locks_mode (lock_name, lock_key);
+CREATE UNIQUE INDEX IF NOT EXISTS worker_read_write_locks_mode_key ON worker_read_write_locks_mode (lock_name, lock_key);
 -- We need this (redundant) constraint so that we can have a foreign key
 -- constraint against this table.
-CREATE UNIQUE INDEX worker_read_write_locks_mode_type ON worker_read_write_locks_mode (lock_name, lock_key, write_lock);
+CREATE UNIQUE INDEX IF NOT EXISTS worker_read_write_locks_mode_type ON worker_read_write_locks_mode (lock_name, lock_key, write_lock);
 
 
 -- A table to track who has currently acquired a given lock.
-CREATE TABLE worker_read_write_locks (
+CREATE TABLE IF NOT EXISTS worker_read_write_locks (
     lock_name TEXT NOT NULL,
     lock_key TEXT NOT NULL,
     -- We write the instance name to ease manual debugging, we don't ever read
@@ -67,6 +67,6 @@ CREATE TABLE worker_read_write_locks (
     FOREIGN KEY (lock_name, lock_key, write_lock) REFERENCES worker_read_write_locks_mode (lock_name, lock_key, write_lock)
 );
 
-CREATE UNIQUE INDEX worker_read_write_locks_key ON worker_read_write_locks (lock_name, lock_key, token);
+CREATE UNIQUE INDEX IF NOT EXISTS 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;
+CREATE UNIQUE INDEX IF NOT EXISTS worker_read_write_locks_write ON worker_read_write_locks (lock_name, lock_key) WHERE write_lock;

synapse/storage/schema/main/delta/79/04_mitigate_stream_ordering_update_race.py

@@ -37,17 +37,17 @@ def run_create(
         # after the background update has finished
         if res:
             drop_cse_sql = """
-            ALTER TABLE current_state_events DROP CONSTRAINT event_stream_ordering_fkey
+            ALTER TABLE current_state_events DROP CONSTRAINT IF EXISTS event_stream_ordering_fkey
             """
             cur.execute(drop_cse_sql)
 
             drop_lcm_sql = """
-            ALTER TABLE local_current_membership DROP CONSTRAINT event_stream_ordering_fkey
+            ALTER TABLE local_current_membership DROP CONSTRAINT IF EXISTS event_stream_ordering_fkey
             """
             cur.execute(drop_lcm_sql)
 
             drop_rm_sql = """
-            ALTER TABLE room_memberships DROP CONSTRAINT event_stream_ordering_fkey
+            ALTER TABLE room_memberships DROP CONSTRAINT IF EXISTS event_stream_ordering_fkey
             """
             cur.execute(drop_rm_sql)