問題

Lock wait timeout exceeded; try restarting transaction

分析

設置了autocommit=0，但沒有提交或者回滾；autocommit是session級別的。如

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

默認設置autocommit=1，但事務沒有正常結束，如

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

解決方案

檢查阻塞的進程並kill掉【推薦】

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;/*排查沒有執行sql，但是佔用事務的進程*/
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 阻塞其他進程的進程*/

檢查程序是否發生異常導致沒有事務沒有正常結束。事務正確的使用方式【推薦】
```
begin;/*start transaction;*/
select * from A where id=1 for update;
...
commit;/*rollback*/
```

查看鎖狀態

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;/*當前進行的事務 lock*/