问题

Lock wait timeout exceeded; try restarting transaction

分析

设置了autocommit=0，但没有提交或者回滚；autocommit是session级别的。如

set autocommit=0;
select * from A where id=1 for update;
...
commit;/*rollback 这里可能被忽略、异常等*/

默认设置autocommit=1，但事务没有正常结束，如

begin;/*start transaction*/
select * from A where id=1 for update;
...
commit;/*rollback 这里可能被忽略、异常等*/

解决方案

检查阻塞的进程并kill掉【推荐】

select * from information_schema.processlist p join information_schema.innodb_trx it on it.trx_mysql_thread_id =p.id where trx_query is null;/*排查没有执行sql，但是占用事务的进程*/
select concat('call mysql.rds_kill(',id,');') from information_schema.processlist p join information_schema.innodb_trx it on it.trx_mysql_thread_id =p.id where trx_query is null;/*kill 阻塞其他进程的进程*/

检查程序是否发生异常导致没有事务没有正常结束。事务正确的使用方式【推荐】
```
begin;/*start transaction;*/
select * from A where id=1 for update;
...
commit;/*rollback*/
```

查看锁状态

select * from information_schema.innodb_locks;

select * from information_schema.innodb_lock_waits ;

select * from information_schema.processlist pl join information_schema.innodb_trx it on pl.id=it.trx_mysql_thread_id join information_schema.innodb_locks il on it.trx_id=il.lock_trx_id;/*当前进行的事务 lock*/