MySQL死鎖檢查處理的正常方法
阿新 • • 發佈：2020-10-22
正常情況下，死鎖發生時，權重最小的連線將被kill並回滾。但是為了找出語句來優化，啟用可啟用死鎖將死鎖資訊記錄下來。
#step 1：視窗一 mysql> start transaction; mysql> update aa set name='aaa' where id = 1; #step 2：視窗二 mysql> start transaction; mysql> update bb set name='bbb' where id = 1; #step 3：視窗一 mysql> update bb set name='bbb';
#step 4：視窗三 #是否自動提交 mysql> show variables like 'autocommit'; +---------------+-------+ | Variable_name | Value | +---------------+-------+ | autocommit | ON | +---------------+-------+ #檢視當前連線 mysql> show processlist; mysql> show full processlist; mysql> SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST; +----+------+-----------+------+---------+------+-------+------------------+ | Id | User | Host | db | Command | Time | State | Info | +----+------+-----------+------+---------+------+-------+------------------+ | 4 | root | localhost | test | Sleep | 244 | | NULL | | 5 | root | localhost | test | Sleep | 111 | | NULL | | 6 | root | localhost | NULL | Query | 0 | init | show processlist | +----+------+-----------+------+---------+------+-------+------------------+ #檢視當前正在被鎖的事務（鎖請求超時後則查不到） mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS; +------------------+-------------+-----------+-----------+-------------+-----------------+------------+-----------+----------+----------------+ | lock_id | lock_trx_id | lock_mode | lock_type | lock_table | lock_index | lock_space | lock_page | lock_rec | lock_data | +------------------+-------------+-----------+-----------+-------------+-----------------+------------+-----------+----------+----------------+ | 130718495:65:3:4 | 130718495 | X | RECORD | `test`.`bb` | GEN_CLUST_INDEX | 65 | 3 | 4 | 0x000000000300 | | 130718496:65:3:4 | 130718496 | X | RECORD | `test`.`bb` | GEN_CLUST_INDEX | 65 | 3 | 4 | 0x000000000300 | +------------------+-------------+-----------+-----------+-------------+-----------------+------------+-----------+----------+----------------+ #檢視當前等待鎖的事務（鎖請求超時後則查不到） mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS; +-------------------+-------------------+-----------------+------------------+ | requesting_trx_id | requested_lock_id | blocking_trx_id | blocking_lock_id | +-------------------+-------------------+-----------------+------------------+ | 130718499 | 130718499:65:3:4 | 130718500 | 130718500:65:3:4 | +-------------------+-------------------+-----------------+------------------+ #檢視當前未提交的事務（如果死鎖等待超時,事務可能還沒有關閉） mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_TRX; +--------------------------------------------------------------------------------------------------------+ | trx_id | trx_state | trx_started | trx_requested_lock_id | trx_wait_started | trx_weight | +-----------+-----------+---------------------+-----------------------+---------------------+------------+ | 130718500 | RUNNING | 2018-03-12 09:28:10 | NULL | NULL | 3 | | 130718499 | LOCK WAIT | 2018-03-12 09:27:59 | 130718499:65:3:4 | 2018-03-12 09:32:48 | 5 | ========================================================================================================== | trx_mysql_thread_id | trx_query | trx_operation_state | trx_tables_in_use | +---------------------+---------------------------------------+---------------------+-------------------+ | 4 | NULL | NULL | 0 | | 5 | update bb set name='bbb' | starting index read | 1 | ========================================================================================================= | trx_tables_locked | trx_lock_structs | trx_lock_memory_bytes | trx_rows_locked | trx_rows_modified | +-------------------+------------------+-----------------------+-----------------+-------------------+ | 0 | 2 | 360 | 3 | 1 | | 1 | 4 | 1184 | 4 | 1 | =========================================================================================================================== | trx_concurrency_tickets | trx_isolation_level | trx_unique_checks | trx_foreign_key_checks | trx_last_foreign_key_error | +-------------------------+---------------------+-------------------+------------------------+----------------------------+ | 0 | REPEATABLE READ | 1 | 1 | NULL | | 0 | REPEATABLE READ | 1 | 1 | NULL | =========================================================================================================================== | trx_adaptive_hash_latched | trx_adaptive_hash_timeout | trx_is_read_only | trx_autocommit_non_locking | +---------------------------+---------------------------+------------------+----------------------------+ | 0 | 10000 | 0 | 0 | | 0 | 10000 | 0 | 0 | +---------------------------+---------------------------+------------------+----------------------------+ #檢視正在被訪問的表 mysql> show OPEN TABLES where In_use > 0; +----------+-------+--------+-------------+ | Database | Table | In_use | Name_locked | +----------+-------+--------+-------------+ | test | bb | 1 | 0 | +----------+-------+--------+-------------+
#step 3：視窗一 （若第三步中鎖請求太久，則出現鎖超時而終止執行） mysql> update bb set name='bbb'; ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction #"視窗一" 鎖請求超時前，執行第五步，使死鎖產生，則該連線 "視窗二" 執行終止，"視窗一" 順利執行 #step 5：視窗二 mysql> update aa set name='aa'; ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction
檢視最近一個死鎖情況
#檢視最近一個死鎖情況 mysql> SHOW ENGINE INNODB STATUS\G ; ............... ------------------------ LATEST DETECTED DEADLOCK ------------------------ 2018-03-12 11:01:06 7ffb4993a700 #發生時間 *** (1) TRANSACTION: #事務1 TRANSACTION 130718515,ACTIVE 19 sec starting index read mysql tables in use 1,locked 1 #正被訪問的表 LOCK WAIT 4 lock struct(s),heap size 1184,4 row lock(s),undo log entries 1 #影響行數 MySQL thread id 5,OS thread handle 0x7ffb498f8700,query id 205 localhost root updating #執行緒/連線host/使用者 update bb set name='bb' #請求語句 *** (1) WAITING FOR THIS LOCK TO BE GRANTED: #等待以下資源 （鎖定位置及鎖模式） 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: #事務2 TRANSACTION 130718516,ACTIVE 14 sec starting index read mysql tables in use 1,locked 1 4 lock struct(s),undo log entries 1 MySQL thread id 4,OS thread handle 0x7ffb4993a700,query id 206 localhost root updating update aa set name='aa' #請求語句 *** (2) HOLDS THE LOCK(S): #持有鎖資源 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) ...............
#死鎖記錄只記錄最近一個死鎖資訊，若要將每個死鎖資訊都儲存到錯誤日誌，啟用以下引數： mysql> show variables like 'innodb_print_all_deadlocks'; +----------------------------+-------+ | Variable_name | Value | +----------------------------+-------+ | innodb_print_all_deadlocks | OFF | +----------------------------+-------+ #上面 【step 3：視窗一】若一直請求不到資源，預設50秒則出現鎖等待超時。 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 #設定全域性變數 鎖等待超時為60秒（新的連線生效） #mysql> set session innodb_lock_wait_timeout=50; mysql> set global innodb_lock_wait_timeout=60; #上面測試中，當事務中的某個語句超時只回滾該語句，事務的完整性屬於被破壞了。為了回滾這個事務，啟用以下引數： mysql> show variables like 'innodb_rollback_on_timeout'; +----------------------------+-------+ | Variable_name | Value | +----------------------------+-------+ | innodb_rollback_on_timeout | OFF | +----------------------------+-------+
最終引數設定如下：(重啟服務重新連線測試)
[mysqld] log-error =/var/log/mysqld3306.log innodb_lock_wait_timeout=60 #鎖請求超時時間(秒) innodb_rollback_on_timeout = 1 #事務中某個語句鎖請求超時將回滾真個事務 innodb_print_all_deadlocks = 1 #死鎖都儲存到錯誤日誌
#若手動刪除堵塞會話，刪除 Command='Sleep' 、無State、無Info、trx_weight 權重最小的。 show processlist; SELECT trx_mysql_thread_id,trx_state,trx_started,trx_weight FROM INFORMATION_SCHEMA.INNODB_TRX;
總結
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