Lock wait timeout exceeded数据库死锁问题

• 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 

• • 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)