问题描述：

数据库从库停止同步。

问题分析：

show slave status\G;（也可使用show full processlist）

显示 某个update语句出错，Lock wait timeout exceeded; try restarting transaction;

原因是这条语句提交的时候超时堵塞。原因在于另外的一个操作开启了事务，锁定了相应的数据，导致这条操作相同数据的sql出错。

示例，在sql中

（1）开启事务，锁定数据

终端A：

MySQL> begin; (开启事务，开启事务会锁定相关数据)
Query OK, 0 rows affected (0.00 sec)

mysql> update pet set sex="m" where name="Fluffy";（修改）
Query OK, 1 row affected (0.03 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from pet;
+--------+--------+---------+------+------------+------------+
| name   | owner  | species | sex  | birth      | death      |
+--------+--------+---------+------+------------+------------+
| Bowser | Diane  | dog     | m    | 1979-08-31 | 1995-07-29 |
| Buffy  | Harold | dog     | f    | 1989-05-13 | NULL       |
| Claws  | Gwen   | cat     | m    | 1994-03-17 | NULL       |
| Fang   | Benny  | dog     | m    | 2013-02-05 | NULL       |
| Fluffy | Harold | cat     | m    | 2012-09-30 | NULL       |
+--------+--------+---------+------+------------+------------+
5 rows in set (0.00 sec)

终端B：

mysql> select * from pet;
+--------+--------+---------+------+------------+------------+
| name   | owner  | species | sex  | birth      | death      |
+--------+--------+---------+------+------------+------------+
| Bowser | Diane  | dog     | m    | 1979-08-31 | 1995-07-29 |
| Buffy  | Harold | dog     | f    | 1989-05-13 | NULL       |
| Claws  | Gwen   | cat     | m    | 1994-03-17 | NULL       |
| Fang   | Benny  | dog     | m    | 2013-02-05 | NULL       |
| Fluffy | Harold | cat     | NULL | 2012-09-30 | NULL       |
+--------+--------+---------+------+------------+------------+
5 rows in set (0.01 sec)

因为没有提交，所以实际上没有改变。但是会锁定Fluffy这一条数据。导致如下的错误。

终端B：

mysql> update pet set sex="m" where name="Fluffy";

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

（2）提交事务，解锁数据

终端A：

mysql> commit;
Query OK, 0 rows affected (0.10 sec)

终端B：

mysql> select * from pet;
+--------+--------+---------+------+------------+------------+
| name   | owner  | species | sex  | birth      | death      |
+--------+--------+---------+------+------------+------------+
| Bowser | Diane  | dog     | m    | 1979-08-31 | 1995-07-29 |
| Buffy  | Harold | dog     | f    | 1989-05-13 | NULL       |
| Claws  | Gwen   | cat     | m    | 1994-03-17 | NULL       |
| Fang   | Benny  | dog     | m    | 2013-02-05 | NULL       |
| Fluffy | Harold | cat     | m    | 2012-09-30 | NULL       |
+--------+--------+---------+------+------------+------------+
5 rows in set (0.00 sec)
mysql> update pet set sex="f" where name="Fluffy";
Query OK, 1 row affected (0.08 sec)
Rows matched: 1  Changed: 1  Warnings: 0

（3）如果where中的条件是索引字段，那么只会锁定索引对应的条目；如果不是索引字段，那么会锁定整张表。

终端A：

mysql> update pet set sex="f" where death="1995-07-29";
Query OK, 1 row affected (0.03 sec)
Rows matched: 1  Changed: 1  Warnings: 0
mysql> select * from pet;
+--------+--------+---------+------+------------+------------+
| name   | owner  | species | sex  | birth      | death      |
+--------+--------+---------+------+------------+------------+
| Bowser | Diane  | dog     | f    | 1979-08-31 | 1995-07-29 |
| Buffy  | Harold | dog     | f    | 1989-05-13 | NULL       |
| Claws  | Gwen   | cat     | m    | 1994-03-17 | NULL       |
| Fang   | Benny  | dog     | m    | 2013-02-05 | NULL       |
| Fluffy | Harold | cat     | f    | 2012-09-30 | NULL       |
+--------+--------+---------+------+------------+------------+
5 rows in set (0.00 sec)

终端B：

mysql> select * from pet;
+--------+--------+---------+------+------------+------------+
| name   | owner  | species | sex  | birth      | death      |
+--------+--------+---------+------+------------+------------+
| Bowser | Diane  | dog     | m    | 1979-08-31 | 1995-07-29 |
| Buffy  | Harold | dog     | f    | 1989-05-13 | NULL       |
| Claws  | Gwen   | cat     | m    | 1994-03-17 | NULL       |
| Fang   | Benny  | dog     | m    | 2013-02-05 | NULL       |
| Fluffy | Harold | cat     | f    | 2012-09-30 | NULL       |
+--------+--------+---------+------+------------+------------+
5 rows in set (0.00 sec)
mysql> update pet set death="2013-07-00" where birth="2013-02-05";

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

解决办法

（1） stop slave;      start slave

(2)网上分析说

Mysql ‘Lock wait timeout exceeded; try restarting transaction‘ 解决方案

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction 
Temporary error: 266: Time-out in NDB, probably caused by deadlock 解决方法：在管理节点的[ndbd default] 
区加：
TransactionDeadLockDetectionTimeOut=10000（设置为10秒）默认是1200（1.2秒）按照顺序重新启动各个节点就不会出现问题了。

不过，本身貌似数据库的TransactionDeadLockDetectionTimeOut已经设置很大，而且即使设置很大，如果那边一直锁表，也是解决不了问题的。