mysql查看死鎖與去除死鎖示例詳解
發(fā)布日期：2022-02-23 09:15 | 文章來(lái)源：源碼中國(guó)
1、查詢進(jìn)程
show processlist
2、 查詢到相對(duì)應(yīng)的進(jìn)程，然后 kill id
驗(yàn)證（kill后再看是否還有鎖）
2、查詢是否鎖表
show OPEN TABLES where In_use > 0;
示例：
新建一個(gè)會(huì)話執(zhí)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(gè)會(huì)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(kù)中增加了三個(gè)關(guān)于鎖的表（innoDB引擎）：
innodb_trx ## 當(dāng)前運(yùn)行的所有事務(wù)
innodb_locks ## 當(dāng)前出現(xiàn)的鎖
innodb_lock_waits ## 鎖等待的對(duì)應(yīng)關(guān)系
先來(lái)看一下這三張表結(jié)構(gòu)：
root@127.0.0.1 : 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(wù)ID | lock_mode | varchar(32) | NO | | | |#鎖模式 | lock_type | varchar(32) | NO | | | |#鎖類型 | 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(hào) | lock_page | bigint(21) unsigned | YES | | NULL | |#被鎖的頁(yè)號(hào) | lock_rec | bigint(21) unsigned | YES | | NULL | |#被鎖的記錄號(hào) | lock_data | varchar(8192) | YES | | NULL | |#被鎖的數(shù)據(jù) +————-+———————+——+—–+———+——-+ 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 | | | |#請(qǐng)求鎖的事務(wù)ID | requested_lock_id | varchar(81) | NO | | | |#請(qǐng)求鎖的鎖ID | blocking_trx_id | varchar(18) | NO | | | |#當(dāng)前擁有鎖的事務(wù)ID | blocking_lock_id | varchar(81) | NO | | | |#當(dāng)前擁有鎖的鎖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 | | | |#事務(wù)ID | trx_state | varchar(13) | NO | | | |#事務(wù)狀態(tài)： | trx_started | datetime | NO | | 0000-00-00 00:00:00 | |#事務(wù)開始時(shí)間； | trx_requested_lock_id | varchar(81) | YES | | NULL | |#innodb_locks.lock_id | trx_wait_started | datetime | YES | | NULL | |#事務(wù)開始等待的時(shí)間 | trx_weight | bigint(21) unsigned | NO | | 0 | |# | trx_mysql_thread_id | bigint(21) unsigned | NO | | 0 | |#事務(wù)線程ID | trx_query | varchar(1024) | YES | | NULL | |#具體SQL語(yǔ)句 | trx_operation_state | varchar(64) | YES | | NULL | |#事務(wù)當(dāng)前操作狀態(tài) | trx_tables_in_use | bigint(21) unsigned | NO | | 0 | |#事務(wù)中有多少個(gè)表被使用 | trx_tables_locked | bigint(21) unsigned | NO | | 0 | |#事務(wù)擁有多少個(gè)鎖 | trx_lock_structs | bigint(21) unsigned | NO | | 0 | |# | trx_lock_memory_bytes | bigint(21) unsigned | NO | | 0 | |#事務(wù)鎖住的內(nèi)存大小（B） | trx_rows_locked | bigint(21) unsigned | NO | | 0 | |#事務(wù)鎖住的行數(shù) | trx_rows_modified | bigint(21) unsigned | NO | | 0 | |#事務(wù)更改的行數(shù) | trx_concurrency_tickets | bigint(21) unsigned | NO | | 0 | |#事務(wù)并發(fā)票數(shù) | trx_isolation_level | varchar(16) | NO | | | |#事務(wù)隔離級(jí)別 | trx_unique_checks | int(1) | NO | | 0 | |#是否唯一性檢查 | trx_foreign_key_checks | int(1) | NO | | 0 | |#是否外鍵檢查 | trx_last_foreign_key_error | varchar(256) | YES | | NULL | |#最后的外鍵錯(cuò)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)
查看正在鎖的事務(wù)
SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS;
查看等待鎖的事務(wù)
SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS;
查看鎖阻塞線程信息
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 ## 線程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, 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 ## 線程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), heap size 360, 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(wú)法分析得到這個(gè)結(jié)果。
從上面來(lái)看，線程4和線程7都在等待往test.emp中的主鍵上加X鎖，page num=3，但是線程7等待的時(shí)間為45s，而線程4等待的時(shí)間為41s，是較線程7之后申請(qǐng)的鎖，所以可以判斷是線程7阻塞了線程4。至于線程7為什么出現(xiàn)等待，這里分析不到根因。
3.3 使用mysqladmin debug查看
# mysqladmin -S /tmp/mysql3306.sock debug
然后在error日志中，會(huì)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，能找到線程ID=3和7是阻塞者，但還是不太準(zhǔn)確，判斷不出來(lái)線程7也是被線程ID=3阻塞的。
3.4 使用innodb_lock_monitor來(lái)獲取阻塞鎖線程
MySQL [test]> CREATE TABLE innodb_lock_monitor (a INT) ENGINE=INNODB; ## 隨便在一個(gè)數(shù)據(jù)庫(kù)中創(chuàng)建這個(gè)表，就會(huì)打開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(gè)在5.6中有一個(gè)warning，但不影響使用。
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 ## 線程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, 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 ## 線程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), 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 ## 這是線程3當(dāng)前正在執(zhí)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 ## 線程3中正在擁有表上的意向IX鎖，并且有test.emp表上主鍵的行級(jí)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 ;;
為什么線程3當(dāng)前執(zhí)行的是一個(gè)select t3表操作，但卻鎖住了test.emp表上page num=3？
有可能是線程3之前對(duì)test.emp表的操作事務(wù)沒有及時(shí)提交導(dǎo)致。
所以得出：線程3阻塞了線程7，而線程7又阻塞了線程4，所以根因就是線程3，讓線程3盡快提交或是kill掉即可。
3.5、 查看表鎖的情況：
mysql> show status like 'table%'; +----------------------------+---------+ | Variable_name | Value | +----------------------------+---------+ | Table_locks_immediate | 100 | | Table_locks_waited | 11 | +----------------------------+---------+
3.6、查看InnoDB_row_lock狀態(tài)變量來(lái)分析系統(tǒng)上的行鎖的爭(zhēng)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(jié)論
在分析innodb中鎖阻塞時(shí)，幾種方法的對(duì)比情況：
（1）使用show processlist查看不靠譜；
（2）直接使用show engine innodb status查看，無(wú)法判斷到問題的根因；
（3）使用mysqladmin debug查看，能看到所有產(chǎn)生鎖的線程，但無(wú)法判斷哪個(gè)才是根因；
（4）開啟innodb_lock_monitor后，再使用show engine innodb status查看，能夠找到鎖阻塞的根因。
參考：https://www.jb51.net/article/201222.htm
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