mysql檢視死鎖與去除死鎖示例詳解

阿新 • • 發佈：2020-12-05

1、查詢程序

show processlist

mysql檢視死鎖與去除死鎖示例詳解

2、查詢到相對應的程序，然後 kill id

mysql檢視死鎖與去除死鎖示例詳解

驗證（kill後再看是否還有鎖）

mysql檢視死鎖與去除死鎖示例詳解

2、查詢是否鎖表

show OPEN TABLES where In_use > 0;

示例：

新建一個會話執行如下的顯示鎖示例

LOCK TABLES account_data.account READ;
SELECT SLEEP(160);
UNLOCK TABLES account_data.account;

另開啟一個會話檢查鎖表情況：

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 庫中增加了三個關於鎖的表（innoDB引擎）：

innodb_trx ## 當前執行的所有事務

innodb_locks ## 當前出現的鎖

innodb_lock_waits ## 鎖等待的對應關係

先來看一下這三張表結構：

[email protected] : information_schema 13:28:38> desc innodb_locks;
+————-+———————+——+—–+———+——-+
| Field  | Type    | Null | Key | Default | Extra |
+————-+———————+——+—–+———+——-+
| lock_id  | varchar(81)   | NO |  |   |  |#鎖ID
| lock_trx_id | varchar(18)   | NO |  |   |  |#擁有鎖的事務ID
| lock_mode | varchar(32)   | NO |  |   |  |#鎖模式
| lock_type | varchar(32)   | NO |  |   |  |#鎖型別
| lock_table | varchar(1024)  | NO |  |   |  |#被鎖的表
| lock_index | varchar(1024)  | YES |  | NULL |  |#被鎖的索引
| lock_space | bigint(21) unsigned | YES |  | NULL |  |#被鎖的表空間號
| lock_page | bigint(21) unsigned | YES |  | NULL |  |#被鎖的頁號
| lock_rec | bigint(21) unsigned | YES |  | NULL |  |#被鎖的記錄號
| lock_data | varchar(8192)  | YES |  | NULL |  |#被鎖的資料
+————-+———————+——+—–+———+——-+
10 rows in set (0.00 sec)
 
[email protected] : information_schema 13:28:56> desc innodb_lock_waits;
+——————-+————-+——+—–+———+——-+
| Field    | Type  | Null | Key | Default | Extra |
+——————-+————-+——+—–+———+——-+
| requesting_trx_id | varchar(18) | NO |  |   |  |#請求鎖的事務ID
| requested_lock_id | varchar(81) | NO |  |   |  |#請求鎖的鎖ID
| blocking_trx_id | varchar(18) | NO |  |   |  |#當前擁有鎖的事務ID
| blocking_lock_id | varchar(81) | NO |  |   |  |#當前擁有鎖的鎖ID
+——————-+————-+——+—–+———+——-+
4 rows in set (0.00 sec)
 
[email protected] : information_schema 13:29:05> desc innodb_trx ;
+—————————-+———————+——+—–+———————+——-+
| Field      | Type    | Null | Key | Default    | Extra |
+—————————-+———————+——+—–+———————+——-+
| trx_id      | varchar(18)   | NO |  |      |  |#事務ID
| trx_state     | varchar(13)   | NO |  |      |  |#事務狀態：
| trx_started    | datetime   | NO |  | 0000-00-00 00:00:00 |  |#事務開始時間；
| trx_requested_lock_id  | varchar(81)   | YES |  | NULL    |  |#innodb_locks.lock_id
| trx_wait_started   | datetime   | YES |  | NULL    |  |#事務開始等待的時間
| trx_weight     | bigint(21) unsigned | NO |  | 0     |  |#
| trx_mysql_thread_id  | bigint(21) unsigned | NO |  | 0     |  |#事務執行緒ID
| trx_query     | varchar(1024)  | YES |  | NULL    |  |#具體SQL語句
| trx_operation_state  | varchar(64)   | YES |  | NULL    |  |#事務當前操作狀態
| trx_tables_in_use   | bigint(21) unsigned | NO |  | 0     |  |#事務中有多少個表被使用
| trx_tables_locked   | bigint(21) unsigned | NO |  | 0     |  |#事務擁有多少個鎖
| trx_lock_structs   | bigint(21) unsigned | NO |  | 0     |  |#
| trx_lock_memory_bytes  | bigint(21) unsigned | NO |  | 0     |  |#事務鎖住的記憶體大小（B）
| trx_rows_locked   | bigint(21) unsigned | NO |  | 0     |  |#事務鎖住的行數
| trx_rows_modified   | bigint(21) unsigned | NO |  | 0     |  |#事務更改的行數
| trx_concurrency_tickets | bigint(21) unsigned | NO |  | 0     |  |#事務併發票數
| trx_isolation_level  | varchar(16)   | NO |  |      |  |#事務隔離級別
| trx_unique_checks   | int(1)    | NO |  | 0     |  |#是否唯一性檢查
| trx_foreign_key_checks  | int(1)    | NO |  | 0     |  |#是否外來鍵檢查
| trx_last_foreign_key_error | varchar(256)  | YES |  | NULL    |  |#最後的外來鍵錯誤
| trx_adaptive_hash_latched | int(1)    | NO |  | 0     |  |#
| trx_adaptive_hash_timeout | bigint(21) unsigned | NO |  | 0     |  |#
+—————————-+———————+——+—–+———————+——-+
22 rows in set (0.01 sec)

檢視正在鎖的事務

SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS;

mysql檢視死鎖與去除死鎖示例詳解

檢視等待鎖的事務

SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS;

mysql檢視死鎖與去除死鎖示例詳解

檢視鎖阻塞執行緒資訊

3.1 使用show processlist檢視

3.2 直接使用show engine innodb status檢視

------------ 
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 ## 執行緒4在等待往test.emp中的主鍵上加X鎖，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 1,1 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 ## 執行緒7在等待往test.emp中的主鍵上加X鎖，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),1 row lock(s) 
MySQL thread id 3,OS thread handle 0x7f953ffce700,query id 110 localhost root cleaning up

我們知道，主要根因還是thread=3引起的，但從innodb status中卻無法分析得到這個結果。

從上面來看，執行緒4和執行緒7都在等待往test.emp中的主鍵上加X鎖，page num=3，但是執行緒7等待的時間為45s，而執行緒4等待的時間為41s，是較執行緒7之後申請的鎖，所以可以判斷是執行緒7阻塞了執行緒4。至於執行緒7為什麼出現等待，這裡分析不到根因。

3.3 使用mysqladmin debug檢視

# mysqladmin -S /tmp/mysql3306.sock debug

然後在error日誌中，會看到：

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

這種方法中，能找到執行緒ID=3和7是阻塞者，但還是不太準確，判斷不出來執行緒7也是被執行緒ID=3阻塞的。

3.4 使用innodb_lock_monitor來獲取阻塞鎖執行緒

MySQL [test]> CREATE TABLE innodb_lock_monitor (a INT) ENGINE=INNODB; ## 隨便在一個數據庫中建立這個表，就會開啟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)

說明：這個在5.6中有一個warning，但不影響使用。

然後再使用show engine innodb status檢視：

------------ 
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,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 ## 執行緒4在等待往test.emp中的主鍵上加X鎖，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 ## 在給主鍵行上加X鎖之前，先要在表上加意向鎖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,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 ## 執行緒7在等待往test.emp中的主鍵上加X鎖，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 ## 在給主鍵行上加X鎖之前，先要在表上加意向鎖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),OS thread handle 0x7f813c659700,query id 147 localhost root Sending data 
select count(*) from t3 a,t3 b ## 這是執行緒3當前正在執行的SQL 
Trx read view will not see trx with id >= 4662,sees < 4659 
TABLE LOCK table `test`.`emp` trx id 4615 lock mode IX ## 執行緒3中正在擁有表上的意向IX鎖，並且有test.emp表上主鍵的行級X鎖，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  ;;

為什麼執行緒3當前執行的是一個select t3表操作，但卻鎖住了test.emp表上page num=3？

有可能是執行緒3之前對test.emp表的操作事務沒有及時提交導致。

所以得出：執行緒3阻塞了執行緒7，而執行緒7又阻塞了執行緒4，所以根因就是執行緒3，讓執行緒3儘快提交或是kill掉即可。

3.5、查看錶鎖的情況：

mysql> show status like 'table%';
+----------------------------+---------+
| Variable_name | Value |
+----------------------------+---------+
| Table_locks_immediate | 100 |
| Table_locks_waited | 11 |
+----------------------------+---------+

3.6、檢視InnoDB_row_lock狀態變數來分析系統上的行鎖的爭奪情況：

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. 結論

在分析innodb中鎖阻塞時，幾種方法的對比情況：

（1）使用show processlist檢視不靠譜；

（2）直接使用show engine innodb status檢視，無法判斷到問題的根因；

（3）使用mysqladmin debug檢視，能看到所有產生鎖的執行緒，但無法判斷哪個才是根因；

（4）開啟innodb_lock_monitor後，再使用show engine innodb status檢視，能夠找到鎖阻塞的根因。

參考：https://www.jb51.net/article/201222.htm

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