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<strong>识别最新的node节点</strong>
查看文件grastate.dat, 默认保存在datadir.状态信息说明如下:

1. 当node节点正常关闭时,seqno正常显示,如下:

However, if the grastate.dat file looks like the example below, the node has crashed:

2. 在node正常运行时seqno为-1值，关闭后如果为-1表示程序crash或没有正常关闭

可以通过wsrep-recover选项得到相应的GTID状态信息
To find the sequence number of the last committed transaction, run mysqld with the --wsrep-recover option. This option will recover the InnoDB table space to a consistent state, print the corresponding GTID into the error log and exit. In the error log, you can see something like this:

<font color="red">手工编辑更新正确的seqno字段值, 再正常启动MySQL</font>
This is the state ID. Edit the grastate.dat file and update the seqno field manually or let mysqld_safe automatically recover it and pass it to the mysqld next time you start it.

3. 如果是下面的状态信息, 表示服务在执行期间做了非事务操作或者因为数据不一致引起的中断.
If the grastate.dat file looks like the example below, the node has either crashed during execution of a non-transactional operation (such as ALTER TABLE) or aborted due to a database inconsistency.

You still can recover the ID of the last committed transaction from InnoDB as described above. However, the recovery is rather meaningless as the node state is probably corrupted and may not even be functional. If there are no other nodes with a well defined state, a thorough database recovery procedure (similar to that on a standalone MySQL server) must be performed on one of the nodes, and this node should be used as a seed node for new cluster. If this is the case, there is no need to preserve the state ID.

<strong>重置quorum</strong>
集群中超过半数的节点出现故障的时候, 其它的节点可能会无法连接到PC(primary Component),这种情况下所有的节点都会返回Unknown command 给查询语句。
我们可以通过重置quorum来重新引导PC:
1. 找出具有最新状态的节点:

最大值即为最新。
2. 在最新状态的节点上执行: