MySQL Router重装后重新连接集群进行引导出现的——此主机中之前已配置过的问题

问题出现的前因：

　　因为重新安装了MySQL Router，然后打算重新连接上目标集群进行MySQL Router的初始化引导，结果报错了！

[root@linux666 system]# mysqlrouter --bootstrap icadmin@linux03:3306  --user root
Please enter MySQL password for icadmin: 
# Bootstrapping system MySQL Router instance...

Error: It appears that a router instance named 'system' has been previously configured in this host. If that instance no longer exists, use the --force option to overwrite it.
[root@linux666 system]# 

　　按提示添加 --force 选项后，虽然能初始化完成，但启动mysqlrouter后，很快MySQL Router所监听的一系列端口就会断开，mysqlrouter自动退出！

[root@linux666 system]# mysqlrouter --bootstrap icadmin@linux03:3306  --user root --force

　　上面那个报错很容易让人误解，以为上次卸载MySQL Router是在本机哪个地方还有没删除干净的配置，其实就算你重装系统只要你主机名(hostname)没换，连接相同的集群还是会报出这个问题来！那么从这里就可以很肯的得知道，这个问题的检测是在集群那边的，也就是集群上有留下MySQL Router初始化引导时留下的记录！！！存在集群的那里了呢？

　　上MySQL官网，看到了这么个命令—— Cluster.listRouters()

　　You can bootstrap multiple instances of MySQL Router against InnoDB Cluster or InnoDB ReplicaSet. From version 8.0.19, to show a list of all registered MySQL Router instances, issue:

Cluster.listRouters()

　　The result provides information about each registered MySQL Router instance, such as its name in the metadata, the hostname, ports, and so on. For example, issue:

mysql-js> Cluster.listRouters()
{
    "clusterName": "example",
    "routers": {
        "ic-1:3306": {
            "hostname": "ic-1:3306",
            "lastCheckIn": "2020-01-16 11:43:45",
            "roPort": 6447,
            "roXPort": 64470,
            "rwPort": 6446,
            "rwXPort": 64460,
            "version": "8.0.19"
        }
    }
}

　　转到集群相关主机上，用MySQL Shell连接上去，获取到集群句柄(var cluster=dba.getCluster('myCluster'))后，执行一下上述命令，果然是有记录在案：

　　执行以下命令将它们移除就好：

mysql-js> cluster.removeRouterMetadata('linux666::');
mysql-js> cluster.removeRouterMetadata('linux666::system');

　　最后到MySQL Router安装机上重新连接上集群进行初始化引导，就Ok了！

　　以前就是关于 MySQL Router “Error: It appears that a router instance named 'system' has been previously configured in this host. If that instance no longer exists, use the --force option to overwrite it.”的解决办法！