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HomeDatabaseMysql Tutorial关于RelayLog无法自动删除的问题(Neither--relay-lognor--relay

今天查看mysql err日志,发现mysql重启时总会有如下日志出现: [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use --relay-log

今天查看mysql err日志,发现mysql重启时总会有如下日志出现:

[Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=liytest-relay-bin' to avoid this problem.

这个警告提示本身的意思,作为slave,为防止因为主机名变更导致relay log文件名无效的问题,最好设置'--relay-log=liytest-relay-bin'

但问题时,我这机器根本就没有开启slave模式,而且数据目录下一直有liytest-relay-bin.000001,relay的出现并且堆积,上网搜索总结一下原因

该实例原先是一个Slave -------导致relay-log 和 relay-log.index的存在

该实例目前已经不是Slave -------由于没有了IO-Thread,导致relay-log-purge 没有起作用( 这也是其他Slave实例没有这种情况的原因,因为IO-thread会做自动rotate操作)。

该实例每天会进行日常备份 -------Flush logs的存在,导致每天会生成一个relay-log

该实例没有配置expire-logs-days ------导致flush logs时,也不会做relay-log清除

简而言之就是: 一个实例如果之前是Slave,而之后停用了(stop slave),且没有配置expire-logs-days的情况下,会出现relay-log堆积的情况。

顺带也和大家分享下MySQL 内部Logrotate的机制
Binary Log rotate机制:
Rotate:每一条binary log写入完成后,都会判断当前文件是否超过 max_binlog_size,如果超过则自动生成一个binlog file
Delete:expire-logs-days 只在 实例启动时 和 flush logs 时判断,如果文件访问时间早于设定值,则purge file

Relay Log rotate 机制:
Rotate:每从Master fetch一个events后,判断当前文件是否超过 max_relay_log_size 如果超过则自动生成一个新的relay-log-file
Delete:purge-relay-log 在SQL Thread每执行完一个events时判断,如果该relay-log 已经不再需要则自动删除

因此建议当slave不再使用时,一定要通过reset slave来取消relaylog,不然即使重启mysql,问题还是一样存在。

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