如何使用mysql 5.6 information schema定位事务锁信息

lovedb 2019-11-08

379

引子

mysql数据库在运行期间，随着业务体量增加及并发会话陡升，可能随时会出现各种性能问题。其中比较常见的一种现象，某一天公司业务人员或客户反馈说某个业务模板突然卡住了，或者开发同学说某个SQL语句不能继续运行了。 mysql 5.6引入的information_schema数据库，可以完美解决上述的问题。它提供一系列的数据视图或表，便于诊断及分析数据库的各种各样的性能问题，对于运维同学真是大大福利。本文主要介绍information_schema与锁相关的几个表，快速定位是哪些会话或事务导致事务操作不能持续。

相关技术概念

information-schema是一个内置的数据库，通过一系列的表，比如：锁方面的表，字符集相关的表，插件相关的表，进程相关的表，视图相关的表，不一而足。运维人员可以通过不同的表的信息，有助于分析各种各样的性能问题。当然，可以结合另一个数据库performance_schema 数据库，诊断数据库的各种各样的性能问题甚至故障情形。

mysql information-schema官方手册，请查阅如下链接
https://dev.mysql.com/doc/refman/5.6/en/information-schema.html

mysql锁相关官方手册，请查阅如下链接
https://dev.mysql.com/doc/refman/5.6/en/innodb-locking-transaction-model.html

information-schema实践

1，数据库版本
[root@standbygtid ~]# mysql -V
mysql  Ver 14.14 Distrib 5.6.25, for Linux (x86_64) using  EditLine wrapper


2，登陆mysql
[root@standbygtid ~]# mysql -uroot -psystem


3，显示事务及锁相关的表
（注：有ORACLE从业经验的同学，类似于oracle 动态性能视图v$session及locked_objects）
mysql> use information_schema;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A


Database changed
mysql> 




mysql> show tables like 'INNODB%';
+----------------------------------------+
| Tables_in_information_schema (INNODB%) |
+----------------------------------------+
| INNODB_LOCKS                           |
| INNODB_TRX                             |
略
| INNODB_LOCK_WAITS                      |


+----------------------------------------+
28 rows in set (0.00 sec)




4，上述几个表的含义
---锁表
（注：锁是什么，就是你需要某种资源，但此时由人家占着，你需要等待，这就是一种锁，锁的目标就是维护数据一致性）
mysql> desc innodb_locks;
+-------------+---------------------+------+-----+---------+-------+
| Field       | Type                | Null | Key | Default | Extra |
+-------------+---------------------+------+-----+---------+-------+
| lock_id     | varchar(81)         | NO   |     |         |       |  锁编号 
| lock_trx_id | varchar(18)         | NO   |     |         |       |  锁所属事务
| lock_mode   | varchar(32)         | NO   |     |         |       |  锁模式
| lock_type   | varchar(32)         | NO   |     |         |       |  锁类型
| lock_table  | varchar(1024)       | NO   |     |         |       |  锁对应表
| lock_index  | varchar(1024)       | YES  |     | NULL    |       |  锁对应索引
| lock_space  | bigint(21) unsigned | YES  |     | NULL    |       |  锁空间
| lock_page   | bigint(21) unsigned | YES  |     | NULL    |       |  锁对应的页面
| lock_rec    | bigint(21) unsigned | YES  |     | NULL    |       |  锁对应的表记录
| lock_data   | varchar(8192)       | YES  |     | NULL    |       |
+-------------+---------------------+------+-----+---------+-------+
10 rows in set (0.00 sec)




---事务表
mysql> desc innodb_trx;
+----------------------------+---------------------+------+-----+---------------------+-------+
| Field                      | Type                | Null | Key | Default             | Extra |
+----------------------------+---------------------+------+-----+---------------------+-------+
| trx_id                     | varchar(18)         | NO   |     |                     |       | 事务编号 
| 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                |       | 事务请求锁编号
| trx_wait_started           | datetime            | YES  |     | NULL                |       | 事务等待开始时间
| trx_weight                 | bigint(21) unsigned | NO   |     | 0                   |       | 事务权重
| trx_mysql_thread_id        | bigint(21) unsigned | NO   |     | 0                   |       | 事务对应的线程
| trx_query                  | varchar(1024)       | YES  |     | NULL                |       | 事务所属的SQL语句
| trx_operation_state        | varchar(64)         | YES  |     | NULL                |       | 
| trx_tables_in_use          | bigint(21) unsigned | NO   |     | 0                   |       |
| trx_tables_locked          | bigint(21) unsigned | NO   |     | 0                   |       |
| trx_lock_structs           | bigint(21) unsigned | NO   |     | 0                   |       |
| trx_lock_memory_bytes      | bigint(21) unsigned | NO   |     | 0                   |       |
| trx_rows_locked            | bigint(21) unsigned | NO   |     | 0                   |       |
| trx_rows_modified          | bigint(21) unsigned | NO   |     | 0                   |       |
| trx_concurrency_tickets    | bigint(21) unsigned | NO   |     | 0                   |       |
| trx_isolation_level        | varchar(16)         | NO   |     |                     |       |
| trx_unique_checks          | int(1)              | NO   |     | 0                   |       |
| trx_foreign_key_checks     | int(1)              | NO   |     | 0                   |       |
| trx_last_foreign_key_error | varchar(256)        | YES  |     | NULL                |       |
| trx_adaptive_hash_latched  | int(1)              | NO   |     | 0                   |       |
| trx_adaptive_hash_timeout  | bigint(21) unsigned | NO   |     | 0                   |       |
| trx_is_read_only           | int(1)              | NO   |     | 0                   |       |
| trx_autocommit_non_locking | int(1)              | NO   |     | 0                   |       |
+----------------------------+---------------------+------+-----+---------------------+-------+
24 rows in set (0.01 sec)




---锁等待表
mysql> desc innodb_lock_waits;
+-------------------+-------------+------+-----+---------+-------+
| Field             | Type        | Null | Key | Default | Extra |
+-------------------+-------------+------+-----+---------+-------+
| requesting_trx_id | varchar(18) | NO   |     |         |       | 请求锁事务编号
| requested_lock_id | varchar(81) | NO   |     |         |       | 请求锁编号
| blocking_trx_id   | varchar(18) | NO   |     |         |       | 持锁事务编号
| blocking_lock_id  | varchar(81) | NO   |     |         |       | 持锁 锁编号
+-------------------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)




5，为了模拟事务，关闭自动提交


（注：生产系统一定要关闭，防止不小心在生产系统产生误操作无法撤回）
mysql> show variables like '%autocommit%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit    | ON    |
+---------------+-------+
1 row in set (0.00 sec)




mysql> set autocommit=off;
Query OK, 0 rows affected (0.01 sec)


mysql> show variables like '%autocommit%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit    | OFF   |
+---------------+-------+
1 row in set (0.00 sec)




6，产生一个事务


--新开一个登陆会话，不提交
（注：如果一提交，则事务马上消失）
mysql> update zxydb.t_go set a=3;
Query OK, 16778789 rows affected (1 min 0.91 sec)
Rows matched: 25168933  Changed: 16778789  Warnings: 0




--在另一会话查看线程信息
mysql> show processlist;
+----+------+-----------+--------------------+---------+------+----------+---------------------------+
| Id | User | Host      | db                 | Command | Time | State    | Info                      |
+----+------+-----------+--------------------+---------+------+----------+---------------------------+
| 28 | root | localhost | information_schema | Query   |   19 | updating | update zxydb.t_go set a=3 |
| 29 | root | localhost | NULL               | Query   |    0 | init     | show processlist          |
+----+------+-----------+--------------------+---------+------+----------+---------------------------+
2 rows in set (0.00 sec)


--查看事务表
mysql> select * from information_schema.innodb_trx\G;
*************************** 1. row ***************************
                    trx_id: 3996                 
                 trx_state: RUNNING              事务运行状态
               trx_started: 2019-11-06 05:46:18  事务开始的时间
     trx_requested_lock_id: NULL
          trx_wait_started: NULL
                trx_weight: 25224373
       trx_mysql_thread_id: 28                   事务所属的线程，对应上述的show processlist之id列
                 trx_query: NULL
       trx_operation_state: NULL
         trx_tables_in_use: 0
         trx_tables_locked: 0
          trx_lock_structs: 55440
     trx_lock_memory_bytes: 8042024
           trx_rows_locked: 25224372
         trx_rows_modified: 25168933             事务影响的表记录数
   trx_concurrency_tickets: 0
       trx_isolation_level: REPEATABLE READ  事务隔离级别
         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
          trx_is_read_only: 0
trx_autocommit_non_locking: 0
1 row in set (0.03 sec)


ERROR: 
No query specified




--由上可见如果没有竞争资源时，不会产生锁
（注：产生锁的前提条件是必须在2个会话以上，当然不包括mysql自身产生的bug）
mysql> select * from information_schema.innodb_locks\G;
Empty set (0.04 sec)


ERROR: 
No query specified


--没有竞资源，当然也不会产生锁等待
mysql> select * from information_schema.innodb_lock_waits\G;
Empty set (0.03 sec)


ERROR: 
No query specified




7，再开启一个新事务会话
（注：更新上述同一个表的记录，即会产生锁等待，因为需要更新同一个表的记录资源）
mysql> set autocommit=off;
Query OK, 0 rows affected (0.01 sec)


mysql> insert into zxydb.t_go select 3,3;










----可见产生了锁信息


mysql> select * from information_schema.innodb_locks\G;
*************************** 1. row ***************************
    lock_id: 3997:6:55726:1          
lock_trx_id: 3997
  lock_mode: X                      锁模式，x表示排它锁，s表示共享锁
  lock_type: RECORD
 lock_table: `zxydb`.`t_go`         锁定表
 lock_index: GEN_CLUST_INDEX        GEN_CLUST_INDEX表示表级锁
 lock_space: 6
  lock_page: 55726
   lock_rec: 1
  lock_data: supremum pseudo-record
*************************** 2. row ***************************
    lock_id: 3996:6:55726:1
lock_trx_id: 3996
  lock_mode: X
  lock_type: RECORD
 lock_table: `zxydb`.`t_go`
 lock_index: GEN_CLUST_INDEX
 lock_space: 6
  lock_page: 55726
   lock_rec: 1
  lock_data: supremum pseudo-record
2 rows in set (0.03 sec)


ERROR: 
No query specified




---同时也产生锁等待信息
mysql> select * from information_schema.innodb_lock_waits\G;
*************************** 1. row ***************************
requesting_trx_id: 3997               请求锁的事务id
requested_lock_id: 3997:6:55726:1
  blocking_trx_id: 3996               持锁的事务id
 blocking_lock_id: 3996:6:55726:1     
1 row in set (0.03 sec)


ERROR: 
No query specified






8，为了方便监控锁等待的信息，可以编写下述SQL语句


---获取持锁会话及等待锁会话更详细的信息
select trx.trx_mysql_thread_id,
       trx.trx_id,
       trx.trx_state,
       trx.trx_started,
       trx.trx_query,
       locks.lock_type,
       locks.lock_table,
       lock_waits.requesting_trx_id,
       lock_waits.blocking_trx_id      
from information_schema.innodb_trx trx inner join information_schema.innodb_locks locks
     on  trx.trx_id=locks.lock_trx_id
                                        inner join information_schema.innodb_lock_waits lock_waits
     on  trx.trx_id=lock_waits.requesting_trx_id
                                        inner join information_schema.innodb_lock_waits lock_waits
     on  trx.trx_id=lock_waits.blocking_trx_id;  




可知，3997事务是等待锁，而3996是持锁，所以如果你想让3997可以继续工作，有几种方法：
1，继续等待3996事务完成
2，完成3996事务
3，杀死3996事务（操作语句为:kill 28,28为事务所属的线程）
+---------------------+--------+-----------+---------------------+-----------------------------------+-----------+----------------+-------------------+-----------------+
| trx_mysql_thread_id | trx_id | trx_state | trx_started         | trx_query                         | lock_type | lock_table     | requesting_trx_id | blocking_trx_id |
+---------------------+--------+-----------+---------------------+-----------------------------------+-----------+----------------+-------------------+-----------------+
|                  30 | 3997   | LOCK WAIT | 2019-11-06 05:51:04 | insert into zxydb.t_go select 3,3 | RECORD    | `zxydb`.`t_go` | 3997              | 3996            |
|                  28 | 3996   | RUNNING   | 2019-11-06 05:46:18 | NULL                              | RECORD    | `zxydb`.`t_go` | NULL              | NULL            |
+---------------------+--------+-----------+---------------------+-----------------------------------+-----------+----------------+-------------------+-----------------+
2 rows in set (0.04 sec)

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如何使用mysql 5.6 information schema定位事务锁信息

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