ODM FINDING:
flushRouterConfig
flushRouterConfig clears the current cluster information cached by a mongos instance and reloads all sharded cluster metadata from the config database.
This forces an update when the configuration database holds data that is newer than the data cached in the mongos process.
WARNING
Do not modify the config data, except as explicitly documented. A config database cannot typically tolerate manual manipulation.
flushRouterConfig is an administrative command that is only available for mongos instances.
mongos 实例会缓存从config db 哪里获得的分片集群元信息

如果会，缓存在什么地方呢？
==》
由于这部分config 信息并不会太多，不太可能超过1MB空间，所以可以想象mongodb 中会有一些fixed area存放这些元信息，但实际探究其并没有什么深意。

描述步骤 请给出 详细命令行 步骤， 否则无法顺利沟通