MySQL 参数

Posted 2020-10-30 杨哥哥

I see a lot of people filtering replication with binlog-do-db, binlog-ignore-db, replicate-do-db, and replicate-ignore-db. Although there are uses for these, they are dangerous and in my opinion, they are overused. For many cases, there’s a safer alternative.
我看到很多人用binlog-do-db, binlog-ignore-db, replicate-do-db, and replicate-ignore-db来过滤哪些库需要主从复制。虽然这4个参数确实能这样做，但我看来这样做是危险的。这4个参数被滥用了。在很多情况下，这有更好安全的选择。


The danger is simple: they don’t work the way you think they do. Consider the following scenario: you set binlog-ignore-db to “garbage” so data in the garbage database (which doesn’t exist on the slave) isn’t replicated. (I’ll come back to this in a second, so if you already see the problem, don’t rush to the comment form.)
为什么危险很简单: 他们并不像你想的那样工作. 想象如下的场景: 你设置了 binlog-ignore-db = garbage, 所以garbage数据库(在slave上不存在这个数据库) 中的数据不会被复制，(待会儿我再讲这个，如果你已经发现问题了，不要急于到评论表单)


Now you do the following:
现在请按操作:

$ mysql
mysql> delete from garbage.junk;
mysql> use garbage;
mysql> update production.users set disabled = 1 where user = "root";

You just broke replication, twice. Once, because your slave is going to execute the first query and there’s no such table “garbage.junk” on the slave. The second time, silently, because the update to production.users isn’t replicated, so now the root user isn’t disabled on the slave.
复制会broke2次, 第一次，因为 slave尝试着去执行第一条语句，但是slave上并没有这样的表”garbage.junk” , 第二次, 隐含的, 因为对production.users表的操作不会被复制,所以root帐号并没有在slave上被禁用掉.


Why? Because binlog-ignore-db doesn’t do what you think. The phrase I used earlier, “data in the garbage database isn’t replicated,” is a fallacy. That’s not what it does. In fact, it filters out binary logging for statements issued from connections whose default database is “garbage.” In other words, filtering is not based on the contents of the query — it is based on what database you USE.
为什么? 因为 binlog-ignore-db 并不像你想的那样执行, 我之前说的, “garbage数据库上的数据不会被复制”是错的, 实际上(数据库)并没有这么做。事实上，他是通过“use 数据库”这种方式来过滤掉到哪些数据库操作不记录到binlog中去的。换句话说, 过滤不是基于查询的字符串的, 而是基于你used的数据库.

mysql> use garbage;
mysql> update production.users set disabled = 1 where user = "root";

像这里的，主库使用garbage，binlog就会忽略掉、不记录紧跟其后的操作，如这里的update production.users set disabled = 1 where user = “root”; 传给从库也就没有这行操作，导致从库没有更新root表。


The other configuration options I mentioned work similarly. The binlog-do-db and binlog-ignore-db statements are particularly dangerous because they keep statements from ever being written to the binary log, which means you can’t use the binary log for point-in-time recovery of your data from a backup.
我提到的其它配置选项也是类似. binlog-do-db 和 binlog-ignore-db 语句是特别危险的，因为它们不将指定的数据库操作写入到binary日志，导致你不能使用二进制日志从备份恢复指定时间的数据.


In a carefully controlled environment, these options can have benefits, but I won’t talk about that here. (We covered that in our book.)
在严格控制的环境中, 这些选项是很有用的，但是我不会谈论这些(这些包含在我们的书中),


The safer alternative is to configure filters on the slave, with options that actually operate on the tables mentioned in the query itself. These are replicate-wild-* options. For example, the safer way to avoid replicating data in the garbage database is to configure replicate-wild-ignore-table=garbage.%. There are still edge cases where that won’t work, but it works in more cases and has fewer gotchas.
安全的替换方案是在 slave上配置过滤, 使用基于查询中真正涉及到的表的选项, 这些是:replicate-wild-* 选项, 例如, 避免复制 garbage数据库中的数据的安全的方案是 配置: replicate-wild-ignore-table=garbage.%. 这样做仍然有一些特殊的情况, 不能正常工作,但可以在更多的情况下正常工作,并且会遇到更少的意外 (gotchas).


If you are confused, you should read the replication rules section of the manual until you know it by heart