mysql 查看死锁和去除死锁
1、查询进程
show processlist
2、 查询到相对应的进程，然后 kill id
验证（kill后再看是否还有锁）
2、查询是否锁表
show OPEN TABLES where In_use > 0;
示例：
新建一个会话执行如下的显示锁示例
LOCK TABLES account_data.account READ; SELECT SLEEP(160); UNLOCK TABLES account_data.account;
另开启一个会话检查锁表情况：
mysql> show OPEN TABLES where In_use > 0; +--------------+---------+--------+-------------+ | Database | Table | In_use | Name_locked | +--------------+---------+--------+-------------+ | account_data | account | 1 | 0 | +--------------+---------+--------+-------------+ 1 row in set (0.00 sec) mysql> select * from information_schema.innodb_locks\G; Empty set, 1 warning (0.00 sec) ERROR: No query specified mysql> show processlist\G; *************************** 1. row *************************** Id: 5 User: root Host: 192.168.0.206:64294 db: NULL Command: Sleep Time: 4051 State: Info: NULL *************************** 2. row *************************** Id: 8 User: root Host: 192.168.0.206:64297 db: NULL Command: Sleep Time: 4042 State: Info: NULL *************************** 3. row *************************** Id: 10 User: root Host: localhost db: NULL Command: Query Time: 0 State: starting Info: show processlist *************************** 4. row *************************** Id: 19 User: root Host: 192.168.0.206:54603 db: account_data Command: Sleep Time: 245 State: Info: NULL *************************** 5. row *************************** Id: 20 User: root Host: 192.168.0.206:54604 db: information_schema Command: Query Time: 20 State: User sleep Info: select sleep(160) 5 rows in set (0.00 sec) ERROR: No query specified mysql>
3、在5.5中，information_schema 库中增加了三个关于锁的表（innoDB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
先来看一下这三张表结构：
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)
查看正在锁的事务
SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS;
查看等待锁的事务
SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS;
查看锁阻塞线程信息
3.1 使用show processlist查看
3.2 直接使用show engine innodb status查看
------------ TRANSACTIONS ------------ Trx id counter 4131 Purge done for trx's n:o < 4119 undo n:o < 0 state: running but idle History list length 126 LIST OF TRANSACTIONS FOR EACH SESSION: ---TRANSACTION 0, not started MySQL thread id 2, OS thread handle 0x7f953ffff700, query id 115 localhost root init show engine innodb status ---TRANSACTION 4130, ACTIVE 41 sec starting index read mysql tables in use 1, locked 1 LOCK WAIT 2 lock struct(s), heap size 360, 1 row lock(s) MySQL thread id 4, OS thread handle 0x7f953ff9d700, query id 112 localhost root updating delete from emp where empno=7788 ------- TRX HAS BEEN WAITING 41 SEC FOR THIS LOCK TO BE GRANTED: ## 等待了41s RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4130 lock_mode X locks rec but not gap waiting Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 ## 线程4在等待往test.emp中的主键上加X锁，page num=3 0: len 4; hex 80001e6c; asc l;; 1: len 6; hex 000000001018; asc ;; 2: len 7; hex 91000001420084; asc B ;; 3: len 5; hex 53434f5454; asc SCOTT;; 4: len 7; hex 414e414c595354; asc ANALYST;; 5: len 4; hex 80001d8e; asc ;; 6: len 4; hex 208794f0; asc ;; 7: len 4; hex 80000bb8; asc ;; 8: SQL NULL; 9: len 4; hex 80000014; asc ;; ------------------ ---TRANSACTION 4129, ACTIVE 45 sec starting index read mysql tables in use 1, locked 1 LOCK WAIT 2 lock struct(s), heap size 360, 1 row lock(s) MySQL thread id 7, OS thread handle 0x7f953ff6c700, query id 111 localhost root updating update emp set sal=3500 where empno=7788 ------- TRX HAS BEEN WAITING 45 SEC FOR THIS LOCK TO BE GRANTED: ## 等待了45s RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4129 lock_mode X locks rec but not gap waiting Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 ## 线程7在等待往test.emp中的主键上加X锁，page num=3 0: len 4; hex 80001e6c; asc l;; 1: len 6; hex 000000001018; asc ;; 2: len 7; hex 91000001420084; asc B ;; 3: len 5; hex 53434f5454; asc SCOTT;; 4: len 7; hex 414e414c595354; asc ANALYST;; 5: len 4; hex 80001d8e; asc ;; 6: len 4; hex 208794f0; asc ;; 7: len 4; hex 80000bb8; asc ;; 8: SQL NULL; 9: len 4; hex 80000014; asc ;; ------------------ ---TRANSACTION 4128, ACTIVE 51 sec 2 lock struct(s), heap size 360, 1 row lock(s) MySQL thread id 3, OS thread handle 0x7f953ffce700, query id 110 localhost root cleaning up
我们知道，主要根因还是thread=3引起的，但从innodb status中却无法分析得到这个结果。
从上面来看，线程4和线程7都在等待往test.emp中的主键上加X锁，page num=3，但是线程7等待的时间为45s，而线程4等待的时间为41s，是较线程7之后申请的锁，所以可以判断是线程7阻塞了线程4。至于线程7为什么出现等待，这里分析不到根因。
3.3 使用mysqladmin debug查看
# mysqladmin -S /tmp/mysql3306.sock debug
然后在error日志中，会看到：
Thread database.table_name Locked/Waiting Lock_type 3 test.t3 Locked - read Low priority read lock 7 test.emp Locked - write High priority write lock
这种方法中，能找到线程ID=3和7是阻塞者，但还是不太准确，判断不出来线程7也是被线程ID=3阻塞的。
3.4 使用innodb_lock_monitor来获取阻塞锁线程
MySQL [test]> CREATE TABLE innodb_lock_monitor (a INT) ENGINE=INNODB; ## 随便在一个数据库中创建这个表，就会打开lock monitor Query OK, 0 rows affected, 1 warning (0.07 sec) MySQL [test]> show warnings\G *************************** 1. row *************************** Level: Warning Code: 131 Message: Using the table name innodb_lock_monitor to enable diagnostic output is deprecated and may be removed in future releases. Use INFORMATION_SCHEMA or PERFORMANCE_SCHEMA tables or SET GLOBAL innodb_status_output=ON. 1 row in set (0.00 sec)
说明：这个在5.6中有一个warning，但不影响使用。
然后再使用show engine innodb status查看：
------------ TRANSACTIONS ------------ Trx id counter 4667 Purge done for trx's n:o < 4659 undo n:o < 0 state: running but idle History list length 138 LIST OF TRANSACTIONS FOR EACH SESSION: ---TRANSACTION 0, not started MySQL thread id 9, OS thread handle 0x7f813c5f7700, query id 152 localhost root init show engine innodb status ---TRANSACTION 4663, ACTIVE 78 sec starting index read mysql tables in use 1, locked 1 LOCK WAIT 2 lock struct(s), heap size 360, 1 row lock(s) MySQL thread id 4, OS thread handle 0x7f813c628700, query id 149 localhost root updating delete from emp where empno=7788 ------- TRX HAS BEEN WAITING 78 SEC FOR THIS LOCK TO BE GRANTED: ## 等待了78s RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4663 lock_mode X locks rec but not gap waiting Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 ## 线程4在等待往test.emp中的主键上加X锁，page num=3 0: len 4; hex 80001e6c; asc l;; 1: len 6; hex 000000001018; asc ;; 2: len 7; hex 91000001420084; asc B ;; 3: len 5; hex 53434f5454; asc SCOTT;; 4: len 7; hex 414e414c595354; asc ANALYST;; 5: len 4; hex 80001d8e; asc ;; 6: len 4; hex 208794f0; asc ;; 7: len 4; hex 80000bb8; asc ;; 8: SQL NULL; 9: len 4; hex 80000014; asc ;; ------------------ TABLE LOCK table `test`.`emp` trx id 4663 lock mode IX ## 在给主键行上加X锁之前，先要在表上加意向锁IX RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4663 lock_mode X locks rec but not gap waiting Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 0: len 4; hex 80001e6c; asc l;; 1: len 6; hex 000000001018; asc ;; 2: len 7; hex 91000001420084; asc B ;; 3: len 5; hex 53434f5454; asc SCOTT;; 4: len 7; hex 414e414c595354; asc ANALYST;; 5: len 4; hex 80001d8e; asc ;; 6: len 4; hex 208794f0; asc ;; 7: len 4; hex 80000bb8; asc ;; 8: SQL NULL; 9: len 4; hex 80000014; asc ;; ---TRANSACTION 4662, ACTIVE 81 sec starting index read mysql tables in use 1, locked 1 LOCK WAIT 2 lock struct(s), heap size 360, 1 row lock(s) MySQL thread id 7, OS thread handle 0x7f813c5c6700, query id 148 localhost root updating update emp set sal=3500 where empno=7788 ------- TRX HAS BEEN WAITING 81 SEC FOR THIS LOCK TO BE GRANTED: ## 等待了81s RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4662 lock_mode X locks rec but not gap waiting Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 ## 线程7在等待往test.emp中的主键上加X锁，page num=3 0: len 4; hex 80001e6c; asc l;; 1: len 6; hex 000000001018; asc ;; 2: len 7; hex 91000001420084; asc B ;; 3: len 5; hex 53434f5454; asc SCOTT;; 4: len 7; hex 414e414c595354; asc ANALYST;; 5: len 4; hex 80001d8e; asc ;; 6: len 4; hex 208794f0; asc ;; 7: len 4; hex 80000bb8; asc ;; 8: SQL NULL; 9: len 4; hex 80000014; asc ;; ------------------ TABLE LOCK table `test`.`emp` trx id 4662 lock mode IX ## 在给主键行上加X锁之前，先要在表上加意向锁IX RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4662 lock_mode X locks rec but not gap waiting Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 0: len 4; hex 80001e6c; asc l;; 1: len 6; hex 000000001018; asc ;; 2: len 7; hex 91000001420084; asc B ;; 3: len 5; hex 53434f5454; asc SCOTT;; 4: len 7; hex 414e414c595354; asc ANALYST;; 5: len 4; hex 80001d8e; asc ;; 6: len 4; hex 208794f0; asc ;; 7: len 4; hex 80000bb8; asc ;; 8: SQL NULL; 9: len 4; hex 80000014; asc ;; ---TRANSACTION 4615, ACTIVE 1579 sec, thread declared inside InnoDB 1222 mysql tables in use 2, locked 0 2 lock struct(s), heap size 360, 1 row lock(s) MySQL thread id 3, OS thread handle 0x7f813c659700, query id 147 localhost root Sending data select count(*) from t3 a,t3 b ## 这是线程3当前正在执行的SQL Trx read view will not see trx with id >= 4662, sees < 4659 TABLE LOCK table `test`.`emp` trx id 4615 lock mode IX ## 线程3中正在拥有表上的意向IX锁，并且有test.emp表上主键的行级X锁，page num=3 RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4615 lock_mode X locks rec but not gap Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 0: len 4; hex 80001e6c; asc l;; 1: len 6; hex 000000001018; asc ;; 2: len 7; hex 91000001420084; asc B ;; 3: len 5; hex 53434f5454; asc SCOTT;; 4: len 7; hex 414e414c595354; asc ANALYST;; 5: len 4; hex 80001d8e; asc ;; 6: len 4; hex 208794f0; asc ;; 7: len 4; hex 80000bb8; asc ;; 8: SQL NULL; 9: len 4; hex 80000014; asc ;;
为什么线程3当前执行的是一个select t3表操作，但却锁住了test.emp表上page num=3？
有可能是线程3之前对test.emp表的操作事务没有及时提交导致。
所以得出：线程3阻塞了线程7，而线程7又阻塞了线程4，所以根因就是线程3，让线程3尽快提交或是kill掉即可。
3.5、 查看表锁的情况：
mysql> show status like 'table%'; +----------------------------+---------+ | Variable_name | Value | +----------------------------+---------+ | Table_locks_immediate | 100 | | Table_locks_waited | 11 | +----------------------------+---------+
3.6、查看InnoDB_row_lock状态变量来分析系统上的行锁的争夺情况：
mysql> show status like 'InnoDB_row_lock%'; +-------------------------------+--------+ | Variable_name | Value | +-------------------------------+--------+ | Innodb_row_lock_current_waits | 0 | | Innodb_row_lock_time | 159372 | | Innodb_row_lock_time_avg | 39843 | | Innodb_row_lock_time_max | 51154 | | Innodb_row_lock_waits | 4 | +-------------------------------+--------+ 5 rows in set (0.01 sec) mysql>
4. 结论
在分析innodb中锁阻塞时，几种方法的对比情况：
（1）使用show processlist查看不靠谱；
（2）直接使用show engine innodb status查看，无法判断到问题的根因；
（3）使用mysqladmin debug查看，能看到所有产生锁的线程，但无法判断哪个才是根因；
（4）开启innodb_lock_monitor后，再使用show engine innodb status查看，能够找到锁阻塞的根因。
参考：http://blog.csdn.net/hw_libo/article/details/39080809
