Hi,
we encountered an strange things:some connects were ok,the others were thrown exception by application for timeout expires and exception.but there were no abnormal information in the mongod syslog.then we modify the connection configure:point out the one of definitized host ip:port(old configure is replicationSet configure,the contant was in the attachment) ,then all connections were ok.Then we install the same architecture:replicateSet in the staging ,the questions were not reappeared.

thanks for your help~~