一 问题描述
执行一个普通的update报错：
ERROR 1205 (HY000): Lock wait timeout exceeded
二 排查思路
查看是否有阻塞：
SELECT
p2.`HOST` Blockedhost,
p2.`USER` BlockedUser,
r.trx_id BlockedTrxId,
r.trx_mysql_thread_id BlockedThreadId,
TIMESTAMPDIFF(
SECOND,
r.trx_wait_started,
CURRENT_TIMESTAMP
) WaitTime,
r.trx_query BlockedQuery,
l.lock_table BlockedTable,
m.`lock_mode` BlockedLockMode,
m.`lock_type` BlockedLockType,
m.`lock_index` BlockedLockIndex,
m.`lock_space` BlockedLockSpace,
m.lock_page BlockedLockPage,
m.lock_rec BlockedLockRec,
m.lock_data BlockedLockData,
p.`HOST` blocking_host,
p.`USER` blocking_user,
b.trx_id BlockingTrxid,
b.trx_mysql_thread_id BlockingThreadId,
b.trx_query BlockingQuery,
l.`lock_mode` BlockingLockMode,
l.`lock_type` BlockingLockType,
l.`lock_index` BlockingLockIndex,
l.`lock_space` BlockingLockSpace,
l.lock_page BlockingLockPage,
l.lock_rec BlockingLockRec,
l.lock_data BlockingLockData,
IF (p.COMMAND = 'Sleep', CONCAT(p.TIME,' seconds'), 0) idel_in_trx
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
INNER JOIN information_schema.INNODB_LOCKS l ON w.blocking_lock_id = l.lock_id AND l.`lock_trx_id`=b.`trx_id`
INNER JOIN information_schema.INNODB_LOCKS m ON m.`lock_id`=w.`requested_lock_id` AND m.`lock_trx_id`=r.`trx_id`
INNER JOIN information_schema. PROCESSLIST p ON p.ID = b.trx_mysql_thread_id
INNER JOIN information_schema. PROCESSLIST p2 ON p2.ID = r.trx_mysql_thread_id
ORDER BY
WaitTime DESC
发现阻塞方竟然是一个commit语句，我们设置的是自动提交呀。
然后执行SELECT * FROM information_schema.processlist WHERE info IS NOT NULL
ORDER BY TIME DESC;发现报错，磁盘空间不足。
发现磁盘空间百分百了，估计是磁盘空间100%，导致无法commit，进而导致无法update。
三 解决办法
清理binlog。示例：
#查看有哪些binlog
SHOW BINARY LOGS;
#清理slave-bin.000395之前的binlog
PURGE BINARY LOGS TO 'slave-bin.000395';