From c46139a17edd0237ab3e6243346e5b5e201e4673 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Thu, 16 Nov 2017 18:07:01 +0000
Subject: [PATCH] Avoid locking account_data tables for upserts

---
 synapse/storage/account_data.py | 85 +++++++++++++++++++--------------
 1 file changed, 49 insertions(+), 36 deletions(-)

diff --git a/synapse/storage/account_data.py b/synapse/storage/account_data.py
index c8a1eb016..56a0bde54 100644
--- a/synapse/storage/account_data.py
+++ b/synapse/storage/account_data.py
@@ -222,9 +222,12 @@ class AccountDataStore(SQLBaseStore):
         """
         content_json = json.dumps(content)
 
-        def add_account_data_txn(txn, next_id):
-            self._simple_upsert_txn(
-                txn,
+        with self._account_data_id_gen.get_next() as next_id:
+            # no need to lock here as room_account_data has a unique constraint
+            # on (user_id, room_id, account_data_type) so _simple_upsert will
+            # retry if there is a conflict.
+            yield self._simple_upsert(
+                desc="add_room_account_data",
                 table="room_account_data",
                 keyvalues={
                     "user_id": user_id,
@@ -234,19 +237,20 @@ class AccountDataStore(SQLBaseStore):
                 values={
                     "stream_id": next_id,
                     "content": content_json,
-                }
+                },
+                lock=False,
             )
-            txn.call_after(
-                self._account_data_stream_cache.entity_has_changed,
-                user_id, next_id,
-            )
-            txn.call_after(self.get_account_data_for_user.invalidate, (user_id,))
-            self._update_max_stream_id(txn, next_id)
 
-        with self._account_data_id_gen.get_next() as next_id:
-            yield self.runInteraction(
-                "add_room_account_data", add_account_data_txn, next_id
-            )
+            # it's theoretically possible for the above to succeed and the
+            # below to fail - in which case we might reuse a stream id on
+            # restart, and the above update might not get propagated. That
+            # doesn't sound any worse than the whole update getting lost,
+            # which is what would happen if we combined the two into one
+            # transaction.
+            yield self._update_max_stream_id(next_id)
+
+            self._account_data_stream_cache.entity_has_changed(user_id, next_id)
+            self.get_account_data_for_user.invalidate((user_id,))
 
         result = self._account_data_id_gen.get_current_token()
         defer.returnValue(result)
@@ -263,9 +267,12 @@ class AccountDataStore(SQLBaseStore):
         """
         content_json = json.dumps(content)
 
-        def add_account_data_txn(txn, next_id):
-            self._simple_upsert_txn(
-                txn,
+        with self._account_data_id_gen.get_next() as next_id:
+            # no need to lock here as account_data has a unique constraint on
+            # (user_id, account_data_type) so _simple_upsert will retry if
+            # there is a conflict.
+            yield self._simple_upsert(
+                desc="add_user_account_data",
                 table="account_data",
                 keyvalues={
                     "user_id": user_id,
@@ -274,40 +281,46 @@ class AccountDataStore(SQLBaseStore):
                 values={
                     "stream_id": next_id,
                     "content": content_json,
-                }
+                },
+                lock=False,
             )
-            txn.call_after(
-                self._account_data_stream_cache.entity_has_changed,
+
+            # it's theoretically possible for the above to succeed and the
+            # below to fail - in which case we might reuse a stream id on
+            # restart, and the above update might not get propagated. That
+            # doesn't sound any worse than the whole update getting lost,
+            # which is what would happen if we combined the two into one
+            # transaction.
+            yield self._update_max_stream_id(next_id)
+
+            self._account_data_stream_cache.entity_has_changed(
                 user_id, next_id,
             )
-            txn.call_after(self.get_account_data_for_user.invalidate, (user_id,))
-            txn.call_after(
-                self.get_global_account_data_by_type_for_user.invalidate,
+            self.get_account_data_for_user.invalidate((user_id,))
+            self.get_global_account_data_by_type_for_user.invalidate(
                 (account_data_type, user_id,)
             )
-            self._update_max_stream_id(txn, next_id)
-
-        with self._account_data_id_gen.get_next() as next_id:
-            yield self.runInteraction(
-                "add_user_account_data", add_account_data_txn, next_id
-            )
 
         result = self._account_data_id_gen.get_current_token()
         defer.returnValue(result)
 
-    def _update_max_stream_id(self, txn, next_id):
+    def _update_max_stream_id(self, next_id):
         """Update the max stream_id
 
         Args:
-            txn: The database cursor
             next_id(int): The the revision to advance to.
         """
-        update_max_id_sql = (
-            "UPDATE account_data_max_stream_id"
-            " SET stream_id = ?"
-            " WHERE stream_id < ?"
+        def _update(txn):
+            update_max_id_sql = (
+                "UPDATE account_data_max_stream_id"
+                " SET stream_id = ?"
+                " WHERE stream_id < ?"
+            )
+            txn.execute(update_max_id_sql, (next_id, next_id))
+        return self.runInteraction(
+            "update_account_data_max_stream_id",
+            _update,
         )
-        txn.execute(update_max_id_sql, (next_id, next_id))
 
     @cachedInlineCallbacks(num_args=2, cache_context=True, max_entries=5000)
     def is_ignored_by(self, ignored_user_id, ignorer_user_id, cache_context):