记一次处理MySql锁等待（Lock wait timeout exceeded）_MySQL

• 环境

  MySQL5.5 

• 现象

  A.数据更新或新增后数据经常自动回滚。

  B.表操作总报 Lock wait timeout exceeded 并长时间无反应

• 解决方法

  A.应急方法：show processlist; kill掉出现问题的进程

  B.根治方法：select * from innodb_trx 查看有是哪些事务占据了表资源。

        C.我的方法：设置MySQL锁等待超时 innodb_lock_wait_timeout=50 ，autocommit=on

• 该类问题导致原因

  据我分析,Mysql的 InnoDB存储引擎是支持事务的，事务开启后没有被主动Commit。导致该资源被长期占用，其他事务在抢占该资源时，因上一个事务的锁而导致抢占失败！因此出现 Lock wait timeout exceeded 

• 接下来是转载的内容

  
  
  

• 转载:http://blog.sina.com.cn/s/blog_6bb63c9e0100s7cb.html

• MySQL 5.5 -- innodb_lock_wait 锁 等待

• 记得以前，当出现：ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction，
  要解决是一件麻烦的事情 ；
  特别是当一个SQL执行完了，但未COMMIT，后面的SQL想要执行就是被锁，超时结束；
  DBA光从数据库无法着手找出源头是哪个SQL锁住了；
  有时候看看show engine innodb status , 并结合 show full processlist; 能暂时解决问题；但一直不能精确定位；

• 在5.5中，information_schema 库中增加了三个关于锁的表（MEMORY引擎）；
  innodb_trx ## 当前运行的所有事务
  innodb_locks ## 当前出现的锁
  innodb_lock_waits ## 锁等待的对应关系

• 看到这个就非常激动 ； 这可是解决了一个大麻烦，先来看一下表结构

• 
  root@127.0.0.1   : information_schema 13:28:38> desc innodb_locks;
  +-------------+---------------------+------+-----+---------+-------+
  | Field | Type | Null | Key | Default | Extra |
  +-------------+---------------------+------+-----+---------+-------+
  | lock_id | varchar(81) | NO | | | |#锁ID
  | lock_trx_id | varchar(18) | NO | | | |#拥有锁的事务ID
  | lock_mode | varchar(32) | NO | | | |#锁模式
  | lock_type | varchar(32) | NO | | | |#锁类型
  | lock_table | varchar(1024) | NO | | | |#被锁的表
  | lock_index | varchar(1024) | YES | | NULL | |#被锁的索引
  | lock_space | bigint(21) unsigned | YES | | NULL | |#被锁的表空间号
  | lock_page | bigint(21) unsigned | YES | | NULL | |#被锁的页号
  | lock_rec | bigint(21) unsigned | YES | | NULL | |#被锁的记录号
  | lock_data | varchar(8192) | YES | | NULL | |#被锁的数据
  +-------------+---------------------+------+-----+---------+-------+
  10 rows in set (0.00 sec)
  
  root@127.0.0.1   : information_schema 13:28:56> desc innodb_lock_waits;
  +-------------------+-------------+------+-----+---------+-------+
  | Field | Type | Null | Key | Default | Extra |
  +-------------------+-------------+------+-----+---------+-------+
  | requesting_trx_id | varchar(18) | NO | | | |#请求锁的事务ID
  | requested_lock_id | varchar(81) | NO | | | |#请求锁的锁ID
  | blocking_trx_id | varchar(18) | NO | | | |#当前拥有锁的事务ID
  | blocking_lock_id | varchar(81) | NO | | | |#当前拥有锁的锁ID
  +-------------------+-------------+------+-----+---------+-------+
  4 rows in set (0.00 sec)
  
  root@127.0.0.1   : information_schema 13:29:05> desc innodb_trx ;
  +----------------------------+---------------------+------+-----+---------------------+-------+
  | Field | Type | Null | Key | Default | Extra |
  +----------------------------+---------------------+------+-----+---------------------+-------+
  | trx_id | varchar(18) | NO | | | |#事务ID
  | trx_state | varchar(13) | NO | | | |#事务状态：
  | trx_started | datetime | NO | | 0000-00-00 00:00:00 | |#事务开始时间；
  | trx_requested_lock_id | varchar(81) | YES | | NULL | |#innodb_locks.lock_id
  | trx_wait_started | datetime | YES | | NULL | |#事务开始等待的时间
  | trx_weight | bigint(21) unsigned | NO | | 0 | |#
  | trx_mysql_thread_id | bigint(21) unsigned | NO | | 0 | |#事务线程ID
  | trx_query | varchar(1024) | YES | | NULL | |#具体SQL语句
  | trx_operation_state | varchar(64) | YES | | NULL | |#事务当前操作状态
  | trx_tables_in_use | bigint(21) unsigned | NO | | 0 | |#事务中有多少个表被使用
  | trx_tables_locked | bigint(21) unsigned | NO | | 0 | |#事务拥有多少个锁
  | trx_lock_structs | bigint(21) unsigned | NO | | 0 | |#
  | trx_lock_memory_bytes | bigint(21) unsigned | NO | | 0 | |#事务锁住的内存大小（B）
  | trx_rows_locked | bigint(21) unsigned | NO | | 0 | |#事务锁住的行数
  | trx_rows_modified | bigint(21) unsigned | NO | | 0 | |#事务更改的行数
  | trx_concurrency_tickets | bigint(21) unsigned | NO | | 0 | |#事务并发票数
  | trx_isolation_level | varchar(16) | NO | | | |#事务隔离级别
  | trx_unique_checks | int(1) | NO | | 0 | |#是否唯一性检查
  | trx_foreign_key_checks | int(1) | NO | | 0 | |#是否外键检查
  | trx_last_foreign_key_error | varchar(256) | YES | | NULL | |#最后的外键错误
  | trx_adaptive_hash_latched | int(1) | NO | | 0 | |#
  | trx_adaptive_hash_timeout | bigint(21) unsigned | NO | | 0 | |#
  +----------------------------+---------------------+------+-----+---------------------+-------+
  22 rows in set (0.01 sec)

• 下面我们来动手看看数据吧：
  ##建立测试数据：
  use test;
  create table tx1
  (id int primary key ,
  c1 varchar(20),
  c2 varchar(30))
  engine=innodb default charset = utf8 ;

• insert into tx1 values
  (1,'aaaa','aaaaa2'),
  (2,'bbbb','bbbbb2'),
  (3,'cccc','ccccc2');

• commit;

• ###产生事务；
  ### Session1
  start transaction;
  update tx1 set c1='heyf',c2='heyf' where id =3 ;

• ## 产生事务，在innodb_trx就有数据 ；
  root@127.0.0.1   : information_schema 13:38:21> select * from innodb_trx G
  *************************** 1. row ***************************
  trx_id: 3669D82
  trx_state: RUNNING
  trx_started: 2010-12-24 13:38:06
  trx_requested_lock_id: NULL
  trx_wait_started: NULL
  trx_weight: 3
  trx_mysql_thread_id: 2344
  trx_query: NULL
  trx_operation_state: NULL
  trx_tables_in_use: 0
  trx_tables_locked: 0
  trx_lock_structs: 2
  trx_lock_memory_bytes: 376
  trx_rows_locked: 1
  trx_rows_modified: 1
  trx_concurrency_tickets: 0
  trx_isolation_level: REPEATABLE READ
  trx_unique_checks: 1
  trx_foreign_key_checks: 1
  trx_last_foreign_key_error: NULL
  trx_adaptive_hash_latched: 0
  trx_adaptive_hash_timeout: 10000
  1 row in set (0.00 sec)

• ### 由于没有产生锁等待，下面两个表没有数据 ；
  root@127.0.0.1   : information_schema 13:38:31> select * from innodb_lock_waits G
  Empty set (0.00 sec)

• root@127.0.0.1   : information_schema 13:38:57> select * from innodb_locks G
  Empty set (0.00 sec)

• #### 产生锁等待
  #### session 2
  start transaction;
  update tx1 set c1='heyfffff',c2='heyffffff' where id =3 ;

• 
  root@127.0.0.1   : information_schema 13:39:01> select * from innodb_trx G
  *************************** 1. row ***************************
  trx_id: 3669D83 ##第2个事务
  trx_state: LOCK WAIT ## 处于等待状态
  trx_started: 2010-12-24 13:40:07
  trx_requested_lock_id: 3669D83:49:3:4 ##请求的锁ID
  trx_wait_started: 2010-12-24 13:40:07
  trx_weight: 2
  trx_mysql_thread_id: 2346 ##线程 ID
  trx_query: update tx1 set c1='heyfffff',c2='heyffffff' where id =3
  trx_operation_state: starting index read
  trx_tables_in_use: 1 ##需要用到1个表
  trx_tables_locked: 1 ##有1个表被锁
  trx_lock_structs: 2
  trx_lock_memory_bytes: 376
  trx_rows_locked: 1
  trx_rows_modified: 0
  trx_concurrency_tickets: 0
  trx_isolation_level: REPEATABLE READ
  trx_unique_checks: 1
  trx_foreign_key_checks: 1
  trx_last_foreign_key_error: NULL
  trx_adaptive_hash_latched: 0
  trx_adaptive_hash_timeout: 10000
  *************************** 2. row ***************************
  trx_id: 3669D82 ##第1个事务
  trx_state: RUNNING
  trx_started: 2010-12-24 13:38:06
  trx_requested_lock_id: NULL
  trx_wait_started: NULL
  trx_weight: 3
  trx_mysql_thread_id: 2344
  trx_query: NULL
  trx_operation_state: NULL
  trx_tables_in_use: 0
  trx_tables_locked: 0
  trx_lock_structs: 2
  trx_lock_memory_bytes: 376
  trx_rows_locked: 1
  trx_rows_modified: 1
  trx_concurrency_tickets: 0
  trx_isolation_level: REPEATABLE READ
  trx_unique_checks: 1
  trx_foreign_key_checks: 1
  trx_last_foreign_key_error: NULL
  trx_adaptive_hash_latched: 0
  trx_adaptive_hash_timeout: 10000
  2 rows in set (0.00 sec)

• root@127.0.0.1   : information_schema 13:40:12> select * from innodb_locks G
  *************************** 1. row ***************************
  lock_id: 3669D83:49:3:4 ## 第2个事务需要的锁
  lock_trx_id: 3669D83
  lock_mode: X
  lock_type: RECORD
  lock_table: `test`.`tx1`
  lock_index: `PRIMARY`
  lock_space: 49
  lock_page: 3
  lock_rec: 4
  lock_data: 3
  *************************** 2. row ***************************
  lock_id: 3669D82:49:3:4 ## 第1个事务需要的锁
  lock_trx_id: 3669D82
  lock_mode: X
  lock_type: RECORD
  lock_table: `test`.`tx1`
  lock_index: `PRIMARY`
  lock_space: 49
  lock_page: 3
  lock_rec: 4
  lock_data: 3
  2 rows in set (0.00 sec)

• root@127.0.0.1   : information_schema 13:40:15> select * from innodb_lock_waits G
  *************************** 1. row ***************************
  requesting_trx_id: 3669D83 ## 请求锁的事务
  requested_lock_id: 3669D83:49:3:4 ## 请求锁的锁ID
  blocking_trx_id: 3669D82 ## 拥有锁的事务
  blocking_lock_id: 3669D82:49:3:4 ## 拥有锁的锁ID
  1 row in set (0.00 sec)