排查Mysql死锁问题

1. 现象

程序提供业务逻辑：接收提交的任务请求，然后执行一个Job
任务卡住不执行了
程序错误日志显示如下错误：

bash 复制代码

scheduleThread error:
com.mysql.cj.jdbc.exceptions.MySQLTransactionRollbackException: Lock wait timeout exceeded; try restarting transaction

2. 排查

2.1 尝试加大数据库锁超时时间（结果无效）

sql 复制代码

-- 查看当前锁超时时间（默认50）
SHOW VARIABLES LIKE 'innodb_lock_wait_timeout';
-- 查看事务超时时间（默认50）  
SHOW VARIABLES LIKE 'lock_wait_timeout';

临时调整（重启后失效）

sql 复制代码

SET GLOBAL innodb_lock_wait_timeout = 120;
SET GLOBAL lock_wait_timeout = 120;

2.2 查询锁等待情况（看到有2个等待）

sql 复制代码

-- 查看正在等待锁的线程
-- mysql8+ 语法不同，详见本文"补充"
SELECT * FROM information_schema.INNODB_LOCKS;
SELECT * FROM information_schema.INNODB_LOCK_WAITS;

2.3 查看当前所有线程（看到有大量线程且时间超过7000秒）

sql 复制代码

-- 查看所有连接线程
SHOW PROCESSLIST;
-- 或者更详细的信息
SELECT * FROM information_schema.PROCESSLIST;

process_id	USER	HOST	DB	COMMAND	TIME	INFO
1744	root	10.10.20.45:62890	rouyi-vue-plus	Sleep	7325	NULL
1757	root	10.10.20.45:62937	rouyi-vue-plus	Sleep	7326	NULL
1778	root	10.10.20.45:63581	rouyi-vue-plus	Sleep	7344	NULL
1739	root	10.10.20.45:62870	rouyi-vue-plus	Sleep	7422	NULL
1759	root	10.10.20.45:62951	rouyi-vue-plus	Sleep	7344	NULL
1756	root	10.10.20.45:62929	rouyi-vue-plus	Sleep	7344	NULL

2.4 查找锁等待相关的线程（显示了一堆线程）

sql 复制代码

-- 查找正在等待锁的线程
SELECT 
    p.ID as process_id,
    p.USER,
    p.HOST, 
    p.DB,
    p.COMMAND,
    p.TIME,
    p.STATE,
    p.INFO
FROM information_schema.PROCESSLIST p
WHERE p.STATE LIKE '%lock%' 
   OR p.COMMAND = 'Sleep' AND p.TIME > 60;

2.5 精确查找阻塞的线程（显示一个阻塞线程1744）

sql 复制代码

-- 查看锁等待关系
SELECT 
    r.trx_id waiting_trx_id,
    r.trx_mysql_thread_id waiting_thread_id,
    r.trx_query waiting_query,
    b.trx_id blocking_trx_id,
    b.trx_mysql_thread_id blocking_thread_id,
    b.trx_query blocking_query
FROM information_schema.innodb_lock_waits w
INNER JOIN information_schema.innodb_trx b ON b.trx_id = w.blocking_trx_id
INNER JOIN information_schema.innodb_trx r ON r.trx_id = w.requesting_trx_id;

waiting_trx_id	waiting_thread_id	waiting_query	blocking_trx_id	blocking_thread_id	blocking_query
487168419	1998	select * from xxl_job_lock where lock_name = 'schedule_lock' for update	486996078	1744	NULL

2.6 查看阻塞线程的详细信息

sql 复制代码

-- 查看阻塞线程1744的详细信息
SELECT 
    ID as process_id,
    USER,
    HOST,
    DB,
    COMMAND,
    TIME as time_seconds,
    STATE,
    INFO
FROM information_schema.PROCESSLIST 
WHERE ID = 1744;

2.7 查看阻塞线程的完整历史

sql 复制代码

-- 查看该线程的完整历史
SELECT * FROM performance_schema.events_statements_history 
WHERE THREAD_ID IN (SELECT THREAD_ID FROM performance_schema.threads WHERE PROCESSLIST_ID = 1744)
ORDER BY EVENT_ID DESC;

线程1744的完整历史记录（简述）

sql 复制代码

# 线程1744的完整历史记录（简述）
# 最后阻塞的原因就是54设置了当前session手动提交事务，55 获取了行锁（select * from xxl_job_lock where lock_name = 'schedule_lock' for update），但始终没有提交。
时间线（从新到旧）：
1. EVENT_ID 55: 获取schedule_lock锁 (当前阻塞状态)
2. EVENT_ID 54: 设置autocommit=0 (开启事务)
3. EVENT_ID 53: 执行复杂查询 (扫描394,197行，耗时644秒！)
4. EVENT_ID 52: 执行另一个复杂查询 (扫描53,388行，耗时243秒)
5. EVENT_ID 51: 设置autocommit=1 (提交前一个事务)
6. EVENT_ID 50: commit (提交事务)
7. EVENT_ID 49: 之前获取schedule_lock锁
8. EVENT_ID 48: 设置autocommit=0

3. 解决

杀掉1744进程（该进程不是正常服务调用产生的进程，是研发连接的一个终端）

sql 复制代码

-- KILL 阻塞的进程 (1744)
KILL 1744;

杀掉1744进程后，阻塞解除

sql 复制代码

-- 验证阻塞是否解除
SELECT 
    r.trx_id waiting_trx_id,
    r.trx_mysql_thread_id waiting_thread,
    b.trx_mysql_thread_id blocking_thread
FROM information_schema.innodb_lock_waits w
INNER JOIN information_schema.innodb_trx b ON b.trx_id = w.blocking_trx_id
INNER JOIN information_schema.innodb_trx r ON r.trx_id = w.requesting_trx_id;

4. 补充

4.1 查看长时间运行的查询

sql 复制代码

-- 查找运行时间超过60秒的查询
SELECT 
    '长时间运行查询' as title;
SELECT 
    ID as process_id,
    USER,
    HOST,
    DB,
    COMMAND,
    TIME,
    STATE,
    LEFT(INFO, 100) as query_snippet
FROM information_schema.PROCESSLIST
WHERE TIME > 60
ORDER BY TIME DESC;

4.2 查看所有线程

sql 复制代码

-- 综合诊断脚本
SELECT 
    '当前进程状态' as title;
SHOW PROCESSLIST;

4.3 查看所有锁等待

sql 复制代码

-- 使用系统库查询
SELECT * FROM sys.innodb_lock_waits;

-- 查看详细信息
-- mysq 5.7 查询
SELECT 
    '锁等待情况' as title;
SELECT 
    r.trx_id waiting_trx_id,
    r.trx_mysql_thread_id waiting_thread,
    r.trx_query waiting_query,
    b.trx_id blocking_trx_id,
    b.trx_mysql_thread_id blocking_thread,
    b.trx_query blocking_query
FROM information_schema.innodb_lock_waits w
INNER JOIN information_schema.innodb_trx b ON b.trx_id = w.blocking_trx_id
INNER JOIN information_schema.innodb_trx r ON r.trx_id = w.requesting_trx_id;

-- mysq 8.4 查询
SELECT 
    '锁等待情况' as title;
SELECT
  r.trx_id waiting_trx_id,
  r.trx_mysql_thread_id waiting_thread,
  r.trx_query waiting_query,
  b.trx_id blocking_trx_id,
  b.trx_mysql_thread_id blocking_thread,
  b.trx_query blocking_query
FROM performance_schema.data_lock_waits w
INNER JOIN information_schema.innodb_trx b
  ON b.trx_id = w.blocking_engine_transaction_id
INNER JOIN information_schema.innodb_trx r
  ON r.trx_id = w.requesting_engine_transaction_id;

sql 复制代码

SELECT 
    '长时间运行查询' as title;
SELECT 
    ID as process_id,
    USER,
    HOST,
    DB,
    COMMAND,
    TIME,
    STATE,
    LEFT(INFO, 100) as query_snippet
FROM information_schema.PROCESSLIST
WHERE TIME > 60
ORDER BY TIME DESC;

4.4 查看最近死锁信息

sql 复制代码

SHOW ENGINE INNODB STATUS;

关注以下信息

TRANSACTIONS（事务部分）

LOCK WAIT：表示有锁等待
lock_mode X：排他锁等待
waiting：正在等待锁
TRX HAS BEEN WAITING 5 SEC：已等待时间

LATEST DETECTED DEADLOCK（最新死锁信息）
锁类型说明

在输出中常见的锁类型

lock_mode X：排他锁（写锁）
lock_mode S：共享锁（读锁）
locks rec but not gap：记录锁
locks gap before rec：间隙锁
locks gap and rec：临键锁（间隙锁+记录锁）
waiting：正在等待该锁