监控mysql锁定状态_mysql InnoDB锁等待的查看及分析
說明：前面已經了解了InnoDB關于在出現鎖等待的時候，會根據參數innodb_lock_wait_timeout的配置，判斷是否需要進行timeout的操作，本文檔介紹在出現鎖等待時候的查看及分析處理；
在InnoDB Plugin之前，一般通過show full processlist和show engine innodb status命令查看當前的數據庫請求，然后再判斷當前事務中鎖的情況。隨著mysql的發展，已經提供更加便捷的方法來監控數據庫中的鎖等待現象了。
在information_schema下面有三張表:INNODB_TRX、INNODB_LOCKS、INNODB_LOCK_WAITS，通過這三張表，可以更簡單地監控當前的事務并分析可能存在的問題。
INNODB_TRX表及結構
Column name
Description
TRX_WEIGHT
The weight of a transaction, reflecting (but not necessarily the exact count of) the number of rows altered and the number of rows locked by the transaction. To resolve a deadlock, InnoDB selects the transaction with the smallest weight as the “victim” to rollback. Transactions that have changed non-transactional tables are considered heavier than others, regardless of the number of altered and locked rows.
TRX_STATE
Transaction execution state. One of RUNNING, LOCK WAIT, ROLLING BACK or COMMITTING.
TRX_STARTED
Transaction start time.
TRX_REQUESTED_LOCK_ID
ID of the lock the transaction is currently waiting for (if TRX_STATE is LOCK WAIT, otherwise NULL). Details about the lock can be found by joining with INNODB_LOCKS on LOCK_ID.
TRX_WAIT_STARTED
Time when the transaction started waiting on the lock (if TRX_STATE is LOCK WAIT, otherwise NULL).
TRX_QUERY
The SQL query that is being executed by the transaction.
TRX_OPERATION_STATE
The transaction's current operation, or NULL.
TRX_TABLES_IN_USE
The number of InnoDB tables used while processing the current SQL statement of this transaction.
TRX_TABLES_LOCKED
Number of InnoDB tables that the current SQL statement has row locks on. (Because these are row locks, not table locks, the tables can usually still be read from and written to by multiple transactions, despite some rows being locked.)
TRX_LOCK_STRUCTS
The number of locks reserved by the transaction.
TRX_LOCK_MEMORY_BYTES
Total size taken up by the lock structures of this transaction in memory.
TRX_ROWS_LOCKED
Approximate number or rows locked by this transaction. The value might include delete-marked rows that are physically present but not visible to the transaction.
TRX_ROWS_MODIFIED
The number of modified and inserted rows in this transaction.
TRX_CONCURRENCY_TICKETS
A value indicating how much work the current transaction can do before being swapped out, as specified by the innodb_concurrency_tickets option.
TRX_ISOLATION_LEVEL
The isolation level of the current transaction.
TRX_UNIQUE_CHECKS
Whether unique checks are turned on or off for the current transaction. (They might be turned off during a bulk data load, for example.)
TRX_FOREIGN_KEY_CHECKS
Whether foreign key checks are turned on or off for the current transaction. (They might be turned off during a bulk data load, for example.)
TRX_LAST_FOREIGN_KEY_ERROR
Detailed error message for last FK error, or NULL.
TRX_ADAPTIVE_HASH_LATCHED
Whether or not the adaptive hash index is locked by the current transaction. (Only a single transaction at a time can modify the adaptive hash index.)
TRX_ADAPTIVE_HASH_TIMEOUT
Whether to relinquish the search latch immediately for the adaptive hash index, or reserve it across calls from MySQL. When there is no AHI contention, this value remains zero and statements reserve the latch until they finish. During times of contention, it counts down to zero, and statements release the latch immediately after each row lookup.
TRX_IS_READ_ONLY
A value of 1 indicates the transaction is read-only. (5.6.4 and up.)
TRX_AUTOCOMMIT_NON_LOCKING
A value of 1 indicates the transaction is a SELECT statement that does not use the FOR UPDATE or LOCK IN SHARED MODE clauses, and is executing with the autocommit setting turned on so that the transaction will only contain this one statement. (5.6.4 and up.) When this column and TRX_IS_READ_ONLY are both 1, InnoDB optimizes the transaction to reduce the overhead associated with transactions that change table data.
比較常用的列：
trx_id:InnoDB存儲引擎內部唯一的事物ID
trx_status:當前事務的狀態
trx_status:事務的開始時間
trx_requested_lock_id：等待事務的鎖ID
trx_wait_started：事務等待的開始時間
trx_weight：事務的權重，反應一個事務修改和鎖定的行數，當發現死鎖需要回滾時，權重越小的值被回滾
trx_mysql_thread_id：MySQL中的進程ID，與show processlist中的ID值相對應
trx_query：事務運行的SQL語句
INNODB_LOCKS
Column name
Description
LOCK_ID
Unique lock ID number, internal to InnoDB. Treat it as an opaque string. Although LOCK_ID currently contains TRX_ID, the format of the data in LOCK_ID is not guaranteed to remain the same in future releases. Do not write programs that parse the LOCK_ID value.
LOCK_TRX_ID
ID of the transaction holding this lock. Details about the transaction can be found by joining with INNODB_TRX on TRX_ID.
LOCK_MODE
Mode of the lock. One of S, X, IS, IX, S_GAP, X_GAP, IS_GAP, IX_GAP, or AUTO_INC for shared, exclusive, intention shared, intention exclusive row locks, shared and exclusive gap locks, intention shared and intention exclusive gap locks, and auto-increment table level lock, respectively. Refer to the sections Section 14.5.3, “InnoDB Lock Modes” and Section 14.5.2, “The InnoDB Transaction Model and Locking” for information on InnoDB locking.
LOCK_TYPE
Type of the lock. One of RECORD or TABLE for record (row) level or table level locks, respectively.
LOCK_TABLE
Name of the table that has been locked or contains locked records.
LOCK_INDEX
Name of the index if LOCK_TYPE='RECORD', otherwise NULL.
LOCK_SPACE
Tablespace ID of the locked record if LOCK_TYPE='RECORD', otherwise NULL.
LOCK_PAGE
Page number of the locked record if LOCK_TYPE='RECORD', otherwise NULL.
LOCK_REC
Heap number of the locked record within the page if LOCK_TYPE='RECORD', otherwise NULL.
LOCK_DATA
Primary key value(s) of the locked record if LOCK_TYPE='RECORD', otherwise NULL. This column contains the value(s) of the primary key column(s) in the locked row, formatted as a valid SQL string (ready to be copied to SQL commands). If there is no primary key then the InnoDB internal unique row ID number is used. If a gap lock is taken for key values or ranges above the largest value in the index, LOCK_DATA reports “supremum pseudo-record”. When the page containing the locked record is not in the buffer pool (in the case that it was paged out to disk while the lock was held), InnoDB does not fetch the page from disk, to avoid unnecessary disk operations. Instead, LOCK_DATA is set to NULL.
INNODB_LOCK_WAITS
Column name
Description
REQUESTING_TRX_ID
ID of the requesting transaction.
REQUESTED_LOCK_ID
ID of the lock for which a transaction is waiting. Details about the lock can be found by joining with INNODB_LOCKS on LOCK_ID.
BLOCKING_TRX_ID
ID of the blocking transaction.
BLOCKING_LOCK_ID
ID of a lock held by a transaction blocking another transaction from proceeding. Details about the lock can be found by joining with INNODB_LOCKS on LOCK_ID.
以上這些表，其實只要知道其中比較常用的字段，就差不多能夠滿足日常的工作需求了，下面通過測試進行演示；
一、準備工作
1、在test下面隨便創建一張表john，并取消自動commit操作，腳本如下：
mysql> use information_schema
Database changed
mysql> select count(*) from tables;
+----------+
| count(*) |
+----------+
|?????? 81 |
+----------+1 row in set (0.06 sec)
mysql>?create table test.john as select * from tables;
Query OK, 82 rows affected (0.29 sec)
Records: 82? Duplicates: 0? Warnings: 0
mysql>?insert into john select * from john;
Query OK, 671744 rows affected (2 min 19.03 sec)
Records: 671744? Duplicates: 0? Warnings: 0
(經過幾次插入后john表的數據671744行)
mysql>?set @@autocommit=0;Query OK, 0 rows affected (0.00 sec)
(取消數據庫的自動commit)
二、進行表john加鎖操作，腳本如下：
mysql> select count(*) from john for update;
+----------+
| count(*) |
+----------+
|? 2686976 |
+----------+
1 row in set (8.19 sec)
在另外一個窗口中監控innodb鎖的狀態；
mysql> SELECT? * FROM INNODB_TRX\G;
*************************** 1. row ***************************
trx_id: B14????????????????????????????????????????????????/請記住該trx_id/
trx_state: RUNNING?????????????????????????????????????? /當前狀態/
trx_started: 2014-11-29 14:07:51
trx_requested_lock_id: NULL
trx_wait_started: NULL
trx_weight: 15905
trx_mysql_thread_id: 10????????????????????????????????? ????????/在process 里面的id值/
trx_query: select count(*) from john for update;????/當前執行的語句/
trx_operation_state: fetching rows
trx_tables_in_use: 1
trx_tables_locked: 1
trx_lock_structs: 15905
trx_lock_memory_bytes: 1554872
trx_rows_locked: 1360743
trx_rows_modified: 0
trx_concurrency_tickets: 0
trx_isolation_level: REPEATABLE READ
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
1 row in set (0.02 sec)
trx_id: B14 只是持有鎖，但并沒有產生鎖等待；
三、模擬鎖等待
3.1 在另外一個窗口中，執行語句：
mysql> select count(*) from john where table_name='CHARACTER_SETS' for update;
3.2 查看當前鎖等待的情況
INNODB_TRX的鎖情況：
mysql> SELECT? * FROM INNODB_TRX\G;
*************************** 1. row ***************************
trx_id: B15
trx_state: LOCK WAIT?????????????????????? //狀態為鎖等待//
trx_started: 2014-11-29 14:12:28
trx_requested_lock_id: B15:0:32777:2
trx_wait_started: 2014-11-29 14:12:28
trx_weight: 2
trx_mysql_thread_id: 10?????????????????????????? //在process里面可以看到相應的狀態//
trx_query: select count(*) from john where table_name='CHARACTER_SETS' for update??????????????? //鎖等待的語句//
trx_operation_state: starting index read
trx_tables_in_use: 1
trx_tables_locked: 1
trx_lock_structs: 2
trx_lock_memory_bytes: 376
trx_rows_locked: 1
trx_rows_modified: 0
trx_concurrency_tickets: 0
trx_isolation_level: REPEATABLE READ
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
*************************** 2. row ***************************
trx_id: B14
trx_state: RUNNING
trx_started: 2014-11-29 14:07:51
trx_requested_lock_id: NULL
trx_wait_started: NULL
trx_weight: 31777
trx_mysql_thread_id: 8
trx_query: NULL
trx_operation_state: NULL
trx_tables_in_use: 0
trx_tables_locked: 0
trx_lock_structs: 31777
trx_lock_memory_bytes: 3094968
trx_rows_locked: 2718752
trx_rows_modified: 0
trx_concurrency_tickets: 0
trx_isolation_level: REPEATABLE READ
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
2 rows in set (0.02 sec)
請注意：因為我們只有模擬兩個session，所以這邊只有兩個會話。(因此一個處于鎖等待，另外一個必然就是持有鎖的對象。實際的生產環境中可能這邊會出現很多列，所以需要用下面的語句才能判斷：鎖等待和持有鎖對象的匹配關系)
3.3 鎖等待和持有鎖的相互關系
mysql> SELECT * FROM INNODB_LOCK_WAITS\G;
*************************** 1. row ***************************
requesting_trx_id: B15
requested_lock_id: B15:0:32777:2
blocking_trx_id: B14
blocking_lock_id: B14:0:32777:2
1 row in set (0.03 sec)
ERROR:
No query specified
通過視圖INNODB_LOCK_WAITS可以清晰的看到B14持有鎖，而B15處于鎖等待；
3.4 鎖等待的原因
mysql> SELECT * FROM INNODB_LOCKS\G;
*************************** 1. row ***************************
lock_id: B15:0:32777:2
lock_trx_id: B15
lock_mode: X
lock_type: RECORD
lock_table: `test`.`john`
lock_index: `GEN_CLUST_INDEX`
lock_space: 0
lock_page: 32777
lock_rec: 2
lock_data: 0x000000640000
*************************** 2. row ***************************
lock_id: B14:0:32777:2
lock_trx_id: B14
lock_mode: X
lock_type: RECORD
lock_table: `test`.`john`
lock_index: `GEN_CLUST_INDEX`
lock_space: 0
lock_page: 32777
lock_rec: 2
lock_data: 0x000000640000
2 rows in set (0.01 sec)
可以看到持有鎖的模式、對象
3.5 在進程里面查看狀態
Id值為8的進程，Info顯示為NULL值，可以推斷當前的session由于未進行commit導致鎖未釋放的；
總結：通過以上幾個視圖，就可以很快速的判斷出鎖等待的對象及原因了，從這上面也可以看出mysql管理更加便捷和容易了；
總結
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