如何调试 MySQL 上超出的锁定等待超时？

How to debug Lock wait timeout exceeded on MySQL?

提问by Matt McCormick

In my production error logs I occasionally see:

在我的生产错误日志中，我偶尔会看到：

SQLSTATE[HY000]: General error: 1205 Lock wait timeout exceeded; try restarting transaction

SQLSTATE[HY000]：一般错误：1205 超出锁定等待超时；尝试重新启动事务

I know which query is trying to access the database at that moment but is there a way to find out which query had the lock at that precise moment?

我知道那个时候哪个查询正在尝试访问数据库，但是有没有办法找出哪个查询在那个时候锁定了？

回答by RolandoMySQLDBA

What gives this away is the word transaction. It is evident by the statement that the query was attempting to change at least one row in one or more InnoDB tables.

给出这个的是交易这个词。从语句中可以明显看出查询试图更改一个或多个 InnoDB 表中的至少一行。

Since you know the query, all the tables being accessed are candidates for being the culprit.

由于您知道查询，因此所有被访问的表都可能成为罪魁祸首。

From there, you should be able to run SHOW ENGINE INNODB STATUS\G

从那里，你应该能够运行 SHOW ENGINE INNODB STATUS\G

You should be able to see the affected table(s)

您应该能够看到受影响的表

You get all kinds of additional Locking and Mutex Information.

您可以获得各种额外的锁定和互斥信息。

Here is a sample from one of my clients:

这是我的一位客户的示例：

mysql> show engine innodb status\G
*************************** 1. row ***************************
  Type: InnoDB
  Name:
Status:
=====================================
110514 19:44:14 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 4 seconds
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 9014315, signal count 7805377
Mutex spin waits 0, rounds 11487096053, OS waits 7756855
RW-shared spins 722142, OS waits 211221; RW-excl spins 787046, OS waits 39353
------------------------
LATEST FOREIGN KEY ERROR
------------------------
110507 21:41:35 Transaction:
TRANSACTION 0 606162814, ACTIVE 0 sec, process no 29956, OS thread id 1223895360 updating or deleting, thread declared inside InnoDB 499
mysql tables in use 1, locked 1
14 lock struct(s), heap size 3024, 8 row lock(s), undo log entries 1
MySQL thread id 3686635, query id 124164167 10.64.89.145 viget updating
DELETE FROM file WHERE file_id in ('6dbafa39-7f00-0001-51f2-412a450be5cc' )
Foreign key constraint fails for table `backoffice`.`attachment`:
,
  CONSTRAINT `attachment_ibfk_2` FOREIGN KEY (`file_id`) REFERENCES `file` (`file_id`)
Trying to delete or update in parent table, in index `PRIMARY` tuple:
DATA TUPLE: 17 fields;
 0: len 36; hex 36646261666133392d376630302d303030312d353166322d343132613435306265356363; asc 6dbafa39-7f00-0001-51f2-412a450be5cc;; 1: len 6; hex 000024214f7e; asc   $!O~;; 2: len 7; hex 000000400217bc; asc    @   ;; 3: len 2; hex 03e9; asc   ;; 4: len 2; hex 03e8; asc   ;; 5: len 36; hex 65666635323863622d376630302d303030312d336632662d353239626433653361333032; asc eff528cb-7f00-0001-3f2f-529bd3e3a302;; 6: len 40; hex 36646234376337652d376630302d303030312d353166322d3431326132346664656366352e6d7033; asc 6db47c7e-7f00-0001-51f2-412a24fdecf5.mp3;; 7: len 21; hex 416e67656c73204e6f7720436f6e666572656e6365; asc Angels Now Conference;; 8: len 34; hex 416e67656c73204e6f7720436f6e666572656e6365204a756c7920392c2032303131; asc Angels Now Conference July 9, 2011;; 9: len 1; hex 80; asc  ;; 10: len 8; hex 8000124a5262bdf4; asc    JRb  ;; 11: len 8; hex 8000124a57669dc3; asc    JWf  ;; 12: SQL NULL; 13: len 5; hex 8000012200; asc    " ;; 14: len 1; hex 80; asc  ;; 15: len 2; hex 83e8; asc   ;; 16: len 4; hex 8000000a; asc     ;;

But in child table `backoffice`.`attachment`, in index `PRIMARY`, there is a record:
PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 30; hex 36646261666133392d376630302d303030312d353166322d343132613435; asc 6dbafa39-7f00-0001-51f2-412a45;...(truncated); 1: len 30; hex 38666164663561652d376630302d303030312d326436612d636164326361; asc 8fadf5ae-7f00-0001-2d6a-cad2ca;...(truncated); 2: len 6; hex 00002297b3ff; asc   "   ;; 3: len 7; hex 80000040070110; asc    @   ;; 4: len 2; hex 0000; asc   ;; 5: len 30; hex 416e67656c73204e6f7720436f6e666572656e636520446f63756d656e74; asc Angels Now Conference Document;;

------------
TRANSACTIONS
------------
Trx id counter 0 620783814
Purge done for trx's n:o < 0 620783800 undo n:o < 0 0
History list length 35
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0 0, not started, process no 29956, OS thread id 1192212800
MySQL thread id 5341758, query id 189708501 127.0.0.1 lwdba
show innodb status
---TRANSACTION 0 620783788, not started, process no 29956, OS thread id 1196472640
MySQL thread id 5341773, query id 189708353 10.64.89.143 viget
---TRANSACTION 0 0, not started, process no 29956, OS thread id 1223895360
MySQL thread id 5341667, query id 189706152 10.64.89.145 viget
---TRANSACTION 0 0, not started, process no 29956, OS thread id 1227888960
MySQL thread id 5341556, query id 189699857 172.16.135.63 lwdba
---TRANSACTION 0 620781112, not started, process no 29956, OS thread id 1222297920
MySQL thread id 5341511, query id 189696265 10.64.89.143 viget
---TRANSACTION 0 620783736, not started, process no 29956, OS thread id 1229752640
MySQL thread id 5339005, query id 189707998 10.64.89.144 viget
---TRANSACTION 0 620783785, not started, process no 29956, OS thread id 1198602560
MySQL thread id 5337583, query id 189708349 10.64.89.145 viget
---TRANSACTION 0 620783469, not started, process no 29956, OS thread id 1224161600
MySQL thread id 5333500, query id 189708478 10.64.89.144 viget
---TRANSACTION 0 620781240, not started, process no 29956, OS thread id 1198336320
MySQL thread id 5324256, query id 189708493 10.64.89.145 viget
---TRANSACTION 0 617458223, not started, process no 29956, OS thread id 1195141440
MySQL thread id 736, query id 175038790 Has read all relay log; waiting for the slave I/O thread to update it
--------
FILE I/O
--------
I/O thread 0 state: waiting for i/o request (insert buffer thread)
I/O thread 1 state: waiting for i/o request (log thread)
I/O thread 2 state: waiting for i/o request (read thread)
I/O thread 3 state: waiting for i/o request (write thread)
Pending normal aio reads: 0, aio writes: 0,
 ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0
519878 OS file reads, 18962880 OS file writes, 13349046 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 6.25 writes/s, 4.50 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 1190, seg size 1192,
174800 inserts, 174800 merged recs, 54439 merges
Hash table size 35401603, node heap has 35160 buffer(s)
0.50 hash searches/s, 11.75 non-hash searches/s
---
LOG
---
Log sequence number 28 1235093534
Log flushed up to   28 1235093534
Last checkpoint at  28 1235091275
0 pending log writes, 0 pending chkp writes
12262564 log i/o's done, 3.25 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 18909316674; in additional pool allocated 1048576
Dictionary memory allocated 2019632
Buffer pool size   1048576
Free buffers       175763
Database pages     837653
Modified db pages  6
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages read 770138, created 108485, written 7795318
0.00 reads/s, 0.00 creates/s, 4.25 writes/s
Buffer pool hit rate 1000 / 1000
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
1 read views open inside InnoDB
Main thread process no. 29956, id 1185823040, state: sleeping
Number of rows inserted 6453767, updated 4602534, deleted 3638793, read 388349505551
0.25 inserts/s, 1.25 updates/s, 0.00 deletes/s, 2.75 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================

1 row in set, 1 warning (0.00 sec)

You should consider increasing the lock wait timeout value for InnoDB by setting the innodb_lock_wait_timeout, default is 50 sec

您应该考虑通过设置innodb_lock_wait_timeout来增加 InnoDB 的锁等待超时值，默认为 50 秒

mysql> show variables like 'innodb_lock_wait_timeout';
+--------------------------+-------+
| Variable_name            | Value |
+--------------------------+-------+
| innodb_lock_wait_timeout | 50    |
+--------------------------+-------+
1 row in set (0.01 sec)

You can set it to higher value in /etc/my.cnfpermanently with this line

您可以/etc/my.cnf使用此行将其永久设置为更高的值

[mysqld]
innodb_lock_wait_timeout=120

and restart mysql. If you cannot restart mysql at this time, run this:

并重新启动mysql。如果此时无法重新启动 mysql，请运行以下命令：

SET GLOBAL innodb_lock_wait_timeout = 120; 

You could also just set it for the duration of your session

您也可以在会话期间设置它

SET innodb_lock_wait_timeout = 120; 

followed by your query

其次是您的查询

回答by Eric L.

As someone mentioned in one of the many SO threads concerning this problem: Sometimes the process that has locked the table shows up as sleeping in the processlist! I was tearing my hair out until I killed all the sleeping threads that were open in the database in question (none were active at the time). That finally unlocked the table and let the update query run.

正如在有关此问题的许多 SO 线程之一中提到的那样：有时锁定表的进程在进程列表中显示为睡眠！我一直在扯头发，直到我杀死了有问题的数据库中打开的所有休眠线程（当时没有一个处于活动状态）。这最终解锁了表并让更新查询运行。

The commenter said something akin to "Sometimes a MySQL thread locks a table, then sleeps while it waits for something non-MySQL-related to happen."

评论者说了一些类似于“有时 MySQL 线程锁定表，然后在等待与 MySQL 无关的事情发生时休眠”的内容。

After re-re-reviewing the show engine innodb statuslog (once I'd tracked down the client responsible for the lock), I noticed the stuck thread in question was listed at the very bottom of the transaction list, beneath the active queries that were about to error out because of the frozen lock:

在重新查看show engine innodb status日志后（一旦我找到了负责锁定的客户端），我注意到有问题的线程被列在事务列表的最底部，在即将出错的活动查询下方由于冻结锁而退出：

------------------
---TRANSACTION 2744943820, ACTIVE 1154 sec(!!)
2 lock struct(s), heap size 376, 2 row lock(s), undo log entries 1
MySQL thread id 276558, OS thread handle 0x7f93762e7710, query id 59264109 [ip] [database] cleaning up
Trx read view will not see trx with id >= 2744943821, sees < 2744943821

(unsure if the "Trx read view" message is related to the frozen lock, but unlike the other active transactions, this one does not show up with the query that was issued and instead claims the transaction is "cleaning up," yet has multiple row locks)

（不确定“Trx read view”消息是否与冻结锁有关，但与其他活动事务不同，此事务不会与发出的查询一起显示，而是声称该事务正在“清理”，但有多个行锁）

The moral of the story is that a transactioncan be active even though the threadis sleeping.

这个故事的寓意是，即使线程处于休眠状态，事务也可以处于活动状态。

回答by Vlad Mihalcea

Due to the popularity of MySQL, there's no wonder Lock wait timeout exceeded; try restarting transactionexception gets so much attention on SO.

由于 MySQL 的流行，难怪超过 Lock wait timeout；尝试重新启动事务异常在 SO 上得到了如此多的关注。

The more contention you have, the greater the chance of deadlocks, which a DB engine will resolve by time-outing one of the deadlocked transactions. Also, long-running transactions that have modified (e.g. UPDATEor DELETE) a large number of entries (which take locks to avoid dirty-write anomalies as explained in the High-Performance Java Persistencebook) are more likely to generate conflicts with other transactions.

争用越多，死锁的可能性就越大，数据库引擎将通过超时死锁事务之一来解决死锁问题。此外，已修改（例如UPDATE或DELETE）大量条目的长时间运行的事务（如高性能 Java 持久性书中所述，使用锁以避免脏写异常）更有可能与其他事务产生冲突。

Although InnoDB MVCC, you can still request explicit locks using the FOR UPDATEclause. However, unlike other popular DBs (Oracle, MSSQL, PostgreSQL, DB2), MySQL uses REPEATABLE_READas the default isolation level.

尽管 InnoDB MVCC，您仍然可以使用FOR UPDATE子句请求显式锁。然而，与其他流行的DB（甲骨文，MSSQL和PostgreSQL，DB2），MySQL的使用REPEATABLE_READ作为默认的隔离级别。

Now, the locks that you acquired (either by modifying rows or using explicit locking), are held for the duration of the currently running transaction. If you want a good explanation of the difference between REPEATABLE_READand READ COMMITTEDin regards to locking, please read this Percona article.

现在，您获得的锁（通过修改行或使用显式锁定）在当前运行的事务期间保持不变。如果您想对锁定REPEATABLE_READ和READ COMMITTED锁定之间的区别有一个很好的解释，请阅读这篇 Percona 文章。

In REPEATABLE READ every lock acquired during a transaction is held for the duration of the transaction.

In READ COMMITTED the locks that did not match the scan are released after the STATEMENT completes.

...

This means that in READ COMMITTED other transactions are free to update rows that they would not have been able to update (in REPEATABLE READ) once the UPDATE statement completes.

在 REPEATABLE READ 中，在事务期间获得的每个锁都会在事务期间保持。

在 READ COMMITTED 中，在 STATEMENT 完成后释放与扫描不匹配的锁。

...

这意味着在 READ COMMITTED 中，一旦 UPDATE 语句完成，其他事务可以自由地更新它们无法更新（在 REPEATABLE READ 中）的行。

Therefore: The more restrictive the isolation level (REPEATABLE_READ, SERIALIZABLE) the greater the chance of deadlock. This is not an issue "per se", it's a trade-off.

因此：隔离级别 ( REPEATABLE_READ, SERIALIZABLE)越严格，死锁的机会就越大。这不是“本身”的问题，而是一种权衡。

You can get very good results with READ_COMMITED, as you need application-level lost update preventionwhen using logical transactions that span over multiple HTTP requests. The optimistic lockingapproach targets lost updatesthat might happen even if you use the SERIALIZABLEisolation levelwhile reducing the lock contention by allowing you to use READ_COMMITED.

使用 可以获得非常好的结果READ_COMMITED，因为在使用跨越多个 HTTP 请求的逻辑事务时，您需要应用程序级别的丢失更新防护。在乐观锁定方法的目标丢失更新可能发生，即使你使用的SERIALIZABLE隔离级别，同时通过允许您使用减少了锁争用READ_COMMITED。

回答by Tomas Bilka

For the record, the lock wait timeout exception happens also when there is a deadlock and MySQL cannot detect it, so it just times out. Another reason might be an extremely long running query, which is easier to solve/repair, however, and I will not describe this case here.

作为记录，当存在死锁并且 MySQL 无法检测到它时，也会发生锁等待超时异常，因此它只是超时。另一个原因可能是运行时间非常长的查询，但是它更容易解决/修复，我不会在这里描述这种情况。

MySQL is usually able to deal with deadlocks if they are constructed "properly" within two transactions. MySQL then just kills/rollback the one transaction that owns fewer locks (is less important as it will impact less rows) and lets the other one finish.

如果在两个事务中“正确”构造死锁，MySQL 通常能够处理死锁。然后 MySQL 只是杀死/回滚拥有较少锁的一个事务（不太重要，因为它会影响较少的行）并让另一个事务完成。

Now, let's suppose there are two processes A and B and 3 transactions:

现在，假设有两个进程 A 和 B 以及 3 个事务：

Process A Transaction 1: Locks X
Process B Transaction 2: Locks Y
Process A Transaction 3: Needs Y => Waits for Y
Process B Transaction 2: Needs X => Waits for X
Process A Transaction 1: Waits for Transaction 3 to finish

(see the last two paragraph below to specify the terms in more detail)

=> deadlock 

This is a very unfortunate setup because MySQL cannot see there is a deadlock (spanned within 3 transactions). So what MySQL does is ... nothing! It just waits, since it does not know what to do. It waits until the first acquired lock exceeds the timeout (Process A Transaction 1: Locks X), then this will unblock the Lock X, which unlocks Transaction 2 etc.

这是一个非常不幸的设置，因为 MySQL 看不到死锁（跨越 3 个事务）。所以 MySQL 所做的是......什么都没有！它只是等待，因为它不知道该做什么。它等待，直到第一个获取的锁超过超时（进程 A 事务 1：锁 X），然后这将解锁锁 X，从而解锁事务 2 等。

The art is to find out what (which query) causes the first lock (Lock X). You will be able to see easily (show engine innodb status) that Transaction 3 waits for Transaction 2, but you will not see which transaction Transaction 2 is waiting for (Transaction 1). MySQL will not print any locks or query associated with Transaction 1. The only hint will be that at the very bottom of the transaction list (of the show engine innodb statusprintout), you will see Transaction 1 apparently doing nothing (but in fact waiting for Transaction 3 to finish).

艺术是找出是什么（哪个查询）导致第一个锁（Lock X）。您将能够轻松看到 ( show engine innodb status) 事务 3 等待事务 2，但您不会看到事务 2 正在等待哪个事务（事务 1）。MySQL 不会打印任何与事务 1 相关的锁或查询。唯一的提示是在事务列表（show engine innodb status打印输出）的最底部，您会看到事务 1 显然什么都不做（但实际上等待事务 3结束）。

The technique for how to find which SQL query causes the lock (Lock X) to be granted for a given transaction that is waiting is described here Tracking MySQL query history in long running transactions

此处描述了如何查找哪个 SQL 查询导致为正在等待的给定事务授予锁 (Lock X) 的技术 Tracking MySQL query history in long running transactions

If you are wondering what the process and the transaction is exactly in the example. The process is a PHP process. Transaction is a transaction as defined by innodb-trx-table. In my case, I had two PHP processes, in each I started a transaction manually. The interesting part was that even though I started one transaction in a process, MySQL used internally in fact two separate transactions (I don't have a clue why, maybe some MySQL dev can explain).

如果您想知道示例中的流程和交易究竟是什么。该进程是一个PHP进程。事务是由innodb-trx-table定义的事务。就我而言，我有两个 PHP 进程，在每个进程中我手动启动了一个事务。有趣的是，尽管我在一个进程中启动了一个事务，但 MySQL 内部实际上使用了两个独立的事务（我不知道为什么，也许某些 MySQL 开发人员可以解释）。

MySQL is managing its own transactions internally and decided (in my case) to use two transactions to handle all the SQL requests coming from the PHP process (Process A). The statement that Transaction 1 is waiting for Transaction 3 to finish is an internal MySQL thing. MySQL "knew" the Transaction 1 and Transaction 3 were actually instantiated as part of one "transaction" request (from Process A). Now the whole "transaction" was blocked because Transaction 3 (a subpart of "transaction") was blocked. Because "transaction" was not able to finish the Transaction 1 (also a subpart of the "transaction") was marked as not finished as well. This is what I meant by "Transaction 1 waits for Transaction 3 to finish".

MySQL 在内部管理自己的事务并决定（就我而言）使用两个事务来处理来自 PHP 进程（进程 A）的所有 SQL 请求。事务 1 正在等待事务 3 完成的语句是 MySQL 内部的事情。MySQL“知道”事务 1 和事务 3 实际上是作为一个“事务”请求（来自进程 A）的一部分实例化的。现在整个“交易”都被阻止了，因为交易 3（“交易”的一个子部分）被阻止了。因为“交易”无法完成交易 1（也是“交易”的一个子部分）也被标记为未完成。这就是我所说的“事务 1 等待事务 3 完成”的意思。

回答by Maruthi

The big problem with this exception is that its usually not reproducible in a test environment and we are not around to run innodb engine status when it happens on prod. So in one of the projects I put the below code into a catch block for this exception. That helped me catch the engine status when the exception happened. That helped a lot.

此异常的最大问题是它通常无法在测试环境中重现，并且当它发生在生产环境中时，我们无法运行 innodb 引擎状态。因此，在其中一个项目中，我将以下代码放入此异常的 catch 块中。这有助于我在异常发生时捕捉引擎状态。那帮助很大。

Statement st = con.createStatement();
ResultSet rs =  st.executeQuery("SHOW ENGINE INNODB STATUS");
while(rs.next()){
    log.info(rs.getString(1));
    log.info(rs.getString(2));
    log.info(rs.getString(3));
}

回答by Andrei Sura

Take a look at the man page of the pt-deadlock-loggerutility:

查看该pt-deadlock-logger实用程序的手册页：

brew install percona-toolkit
pt-deadlock-logger --ask-pass server_name

It extracts information from the engine innodb statusmentioned above and also it can be used to create a daemonwhich runs every 30 seconds.

它从engine innodb status上面提到的信息中提取信息，也可以用来创建daemon每 30 秒运行一次的信息。

回答by Ellert van Koperen

Extrapolating from Rolando's answer above, it is these that are blocking your query:

从上面罗兰多的回答推断，正是这些阻止了您的查询：

---TRANSACTION 0 620783788, not started, process no 29956, OS thread id 1196472640
MySQL thread id 5341773, query id 189708353 10.64.89.143 viget

If you need to execute your query and can not wait for the others to run, kill them off using the MySQL thread id:

如果您需要执行您的查询并且不能等待其他人运行，请使用 MySQL 线程 id 将它们关闭：

kill 5341773 <replace with your thread id>

^{(from within mysql, not the shell, obviously)}

^{（显然是在 mysql 中，而不是在 shell 中）}

You have to find the thread IDs from the:

您必须从以下位置找到线程 ID：

show engine innodb status\G

command, and figure out which one is the one that is blocking the database.

命令，并找出哪个是阻塞数据库的那个。

回答by Slawomir

Here is what I ultimately had to do to figure out what "other query" caused the lock timeout problem. In the application code, we track all pending database calls on a separate thread dedicated to this task. If any DB call takes longer than N-seconds (for us it's 30 seconds) we log:

这是我最终必须做的事情才能弄清楚是什么“其他查询”导致了锁定超时问题。在应用程序代码中，我们在专用于此任务的单独线程上跟踪所有挂起的数据库调用。如果任何数据库调用花费的时间超过 N 秒（对我们来说是 30 秒），我们会记录：

-- Pending InnoDB transactions
SELECT * FROM information_schema.innodb_trx ORDER BY trx_started; 

-- Optionally, log what transaction holds what locks
SELECT * FROM information_schema.innodb_locks;

With above, we were able to pinpoint concurrent queries that locked the rows causing the deadlock. In my case, they were statements like INSERT ... SELECTwhich unlike plain SELECTs lock the underlying rows. You can then reorganize the code or use a different transaction isolation like read uncommitted.

通过以上，我们能够查明锁定导致死锁的行的并发查询。就我而言，它们是类似于INSERT ... SELECT普通 SELECT 锁定底层行的语句。然后，您可以重新组织代码或使用不同的事务隔离，例如未提交读。

Good luck!

祝你好运！

回答by Gerrit Brink

You can use:

您可以使用：

show full processlist

which will list all the connections in MySQL and the current state of connection as well as the query being executed. There's also a shorter variant show processlist;which displays the truncated query as well as the connection stats.

它将列出 MySQL 中的所有连接和连接的当前状态以及正在执行的查询。还有一个较短的变体show processlist;，用于显示截断的查询以及连接统计信息。

回答by th3sly

If you're using JDBC, then you have the option
includeInnodbStatusInDeadlockExceptions=true

如果您使用的是 JDBC，那么您可以选择
includeInnodbStatusInDeadlockExceptions=true

https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-configuration-properties.html

https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-configuration-properties.html