node.js中连接mongodb(Please ensure that you set the default write...)解决办法

Please ensure that you set the default write concern for the database by setting    =

=   one of the options                                                                 =

=                                                                                      =

=     w: (value of > -1 or the string 'majority'), where < 1 means                     =

=        no write acknowlegement                                                       =

=     journal: true/false, wait for flush to journal before acknowlegement             =

=     fsync: true/false, wait for flush to file system before acknowlegement           =

=                                                                                      =

=  For backward compatibility safe is still supported and                              =

=   allows values of [true | false | {j:true} | {w:n, wtimeout:n} | {fsync:true}]      =

=   the default value is false which means the driver receives does not                =

=   return the information of the success/error of the insert/update/remove            =

=                                                                                      =

=   ex: new Db(new Server('localhost', 27017), {safe:false})                           =

=                                                                                      =

=   http://www.mongodb.org/display/DOCS/getLastError+Command                           =

=                                                                                      =

=  The default of no acknowlegement will change in the very near future                =

=                                                                                      =

=  This message will disappear when the default safe is set on the driver Db           =

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new Db(new Server('localhost', 27017), {w: 1})

这样子就可以了