MySQL死锁检查处理的正常方法

正常情况下,死锁发生时,权重最小的连接将被kill并回滚。但是为了找出语句来优化,启用可启用死锁将死锁信息记录下来。

#step 1:窗口一
mysql> start transaction;
mysql> update aa set name='aaa' where id = 1;
 
#step 2:窗口二
mysql> start transaction;
mysql> update bb set name='bbb' where id = 1;
 
#step 3:窗口一
mysql> update bb set name='bbb';
#step 4:窗口三
#是否自动提交
mysql> show variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit |>
#step 3:窗口一 (若第三步中锁请求太久,则出现锁超时而终止执行)
mysql> update bb set name='bbb';
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction
 
 
#"窗口一" 锁请求超时前,执行第五步,使死锁产生,则该连接 "窗口二" 执行终止,"窗口一" 顺利执行
#step 5:窗口二
mysql> update aa set name='aa';
ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction

查看最近一个死锁情况

#查看最近一个死锁情况
mysql> SHOW ENGINE INNODB STATUS\G ;
...............
------------------------
LATEST DETECTED DEADLOCK
------------------------
2018-03-12 11:01:06 7ffb4993a700 #发生时间
*** (1) TRANSACTION: #事务1
TRANSACTION 130718515, ACTIVE 19 sec starting index read
mysql tables in use 1, locked 1 #正被访问的表
LOCK WAIT 4 lock struct(s), heap size 1184, 4 row lock(s), undo log entries 1 #影响行数
MySQL thread id 5, OS thread handle 0x7ffb498f8700, query id 205 localhost root updating #线程/连接host/用户
update bb set name='bb' #请求语句
*** (1) WAITING FOR THIS LOCK TO BE GRANTED: #等待以下资源 (锁定位置及锁模式)
RECORD LOCKS space id 65 page no 3 n bits 72 index `GEN_CLUST_INDEX` of table `test`.`bb` trx id 130718515 lock_mode X waiting
Record lock, heap no 5 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
 0: len 6; hex 000000000300; asc  ;;
 1: len 6; hex 000007ca9b34; asc  4;;
 2: len 7; hex 1f000002092075; asc  u;;
 3: len 4; hex 80000001; asc  ;;
 4: len 2; hex 6262; asc bb;;
 
*** (2) TRANSACTION: #事务2
TRANSACTION 130718516, ACTIVE 14 sec starting index read
mysql tables in use 1, locked 1
4 lock struct(s), heap size 1184, 4 row lock(s), undo log entries 1
MySQL thread id 4, OS thread handle 0x7ffb4993a700, query id 206 localhost root updating
update aa set name='aa' #请求语句
*** (2) HOLDS THE LOCK(S): #持有锁资源
RECORD LOCKS space id 65 page no 3 n bits 72 index `GEN_CLUST_INDEX` of table `test`.`bb` trx id 130718516 lock_mode X
Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
 0: len 8; hex 73757072656d756d; asc supremum;;
 
Record lock, heap no 3 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
 0: len 6; hex 000000000301; asc  ;;
 1: len 6; hex 000007ca9b17; asc  ;;
 2: len 7; hex 9000000144011e; asc  D ;;
 3: len 4; hex 80000002; asc  ;;
 4: len 2; hex 6262; asc bb;;
 
Record lock, heap no 5 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
 0: len 6; hex 000000000300; asc  ;;
 1: len 6; hex 000007ca9b34; asc  4;;
 2: len 7; hex 1f000002092075; asc  u;;
 3: len 4; hex 80000001; asc  ;;
 4: len 2; hex 6262; asc bb;;
 
*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 64 page no 3 n bits 80 index `GEN_CLUST_INDEX` of table `test`.`aa` trx id 130718516 lock_mode X waiting
Record lock, heap no 7 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
 0: len 6; hex 000000000200; asc  ;;
 1: len 6; hex 000007ca9b33; asc  3;;
 2: len 7; hex 1e000001d53057; asc  0W;;
 3: len 4; hex 80000001; asc  ;;
 4: len 2; hex 6161; asc aa;;
 
*** WE ROLL BACK TRANSACTION (2)
...............
#死锁记录只记录最近一个死锁信息,若要将每个死锁信息都保存到错误日志,启用以下参数:
mysql> show variables like 'innodb_print_all_deadlocks';
+----------------------------+-------+
| Variable_name    | Value |
+----------------------------+-------+
| innodb_print_all_deadlocks | OFF |
+----------------------------+-------+
 
 
#上面 【step 3:窗口一】若一直请求不到资源,默认50秒则出现锁等待超时。
mysql> show variables like 'innodb_lock_wait_timeout'; 
+--------------------------+-------+
| Variable_name   | Value |
+--------------------------+-------+
| innodb_lock_wait_timeout | 50 |
+--------------------------+-------+
 
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction
 
 
#设置全局变量 锁等待超时为60秒(新的连接生效)
#mysql> set session innodb_lock_wait_timeout=50; 
mysql> set global innodb_lock_wait_timeout=60; 
 
 
#上面测试中,当事务中的某个语句超时只回滚该语句,事务的完整性属于被破坏了。为了回滚这个事务,启用以下参数:
mysql> show variables like 'innodb_rollback_on_timeout';
+----------------------------+-------+
| Variable_name    | Value |
+----------------------------+-------+
| innodb_rollback_on_timeout | OFF |
+----------------------------+-------+

MySQL死锁检查处理的正常方法

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