MongDB from execCommand not master

 count failed: not master{ "note" : "from execCommand", "ok" : 0, "errmsg" : "not master" } at 

src/mongo/shell/query.js:191

在SECONDARY节点无法show dbs

主从启动之后，连接slave可以成功连上，但是在slave中执行 show dbs 的时候就报错了:

QUERY    Error: listDatabases failed:{ "note" : "from execCommand", "ok" : 0, "errmsg" : "not master" }
解决方法：

在报错的slave机器上执行 rs.slaveOk()方法即可。

解释一下具体slaveOk方法是什么意思？

Provides a shorthand for the following operation:

db.getMongo().setSlaveOk()
This allows the current connection to allow read operations to run on secondary members. See the readPref() 

method for more fine-grained control over read preference in the mongo shell.