mysql常见异常

MySQLTransactionRollbackException : Lock wait timeout exceeded; try restarting transaction

出现
com.mysql.cj.jdbc.exceptions.MySQLTransactionRollbackException: Lock wait timeout exceeded; try restarting transaction
时继续计算下一个分群，导致 FileNotFound /_temporary/0

InnoDB事务在放弃前等待行锁的时间（秒）。innodb_lock_wait_timeout默认值为50秒。
当有试图访问被另一行锁定的行的事务InnoDB事务在发出以下错误：
Lock wait timeout exceeded; try restarting transaction

SHOW GLOBAL VARIABLES LIKE 'innodb_lock_wait_timeout';
SET GLOBAL innodb_lock_wait_timeout=500;

查看有哪些线程正在执行：show processlist;
查看当前运行的所有事务：SELECT * FROM information_schema.INNODB_TRX;
其中trx_mysql_thread_id 与 show processlist;的 id 相对应
查看当前锁定的事务：SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS;
查看当前等锁的事务：SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS;

SQL Error 1040: Too Many Connection

show variables like "max_connections";