python - 为什么 Python/Django 不会在 Mysql : ERROR 1205 (HY000): Lock wait timeout exceeded 上引发异常

Question

我正在通过 python/django 在我的 MySQL 数据库中测试锁定。

我有一张 table ，我正在测试:

CREATE TABLE `test` (
  `id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert into test (id) values (1), (2);
commit;

我有 3 个 session : - 2个mysql控制台 - 1 个 Django View

控制台 1:

mysql> begin; select t.id from test as where id = 1 t FOR UPDATE;
Query OK, 0 rows affected (0.00 sec)

+----+
| id |
+----+
|  1 |
+----+
1 row in set (0.00 sec)

控制台 2:

mysql> set @@session.innodb_lock_wait_timeout = 1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> select t.id from test as t FOR UPDATE;
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

mysql> select t.id from test as t where id = 1 FOR UPDATE;
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

Django View :

@db.transaction.commit_manually
def Test(request):
  c = db.connection.cursor()
  c.execute('set @@session.innodb_lock_wait_timeout = 1')
  c.execute('select t.id from test as t FOR UPDATE')
  logging.error(c.fetchall())
  c.execute('select t.id from test as t where id = 1 FOR UPDATE')
  logging.error(c.fetchall())
  db.transaction.rollback()

  return render_to_response(
      'test.html',
      context_instance=template.RequestContext(request, {})
      )

调用此 View 后，我预计会出现异常，但什么也没有发生，它返回一个空结果集。

有什么想法吗？

版本:

• python :2.7.3
• Django :1.4.3
• MySQL:5.5

谢谢，丹尼尔

Answer 1

You are using a transaction; autocommit does not disable transactions, it just makes them automatically commit at the end of the statement.

What is happening is, some other thread is holding a record lock on some record for too long, and your thread is being timed out.

Source: Getting "Lock wait timeout exceeded; try restarting transaction" even though I'm not using a transaction

您应该通过设置 innodb_lock_wait_timeout=50(默认值)或将其设置为更高的值并重新启动 MySQL 来增加 InnoDB 的锁定等待超时值。