之前项目中用的是 1.12.3 版本的 mongo gem，后来升级 mongo gem 后发现之前版本的链接方式都换了，想再退回到 1.12.3 版本的 GEM 但使用副本集的时候

client =MongoReplicaSetClient.new(['123.57.xxx.xxx:30000', '123.56.xxx.xxx:30000', '101.201.xxx.xxx:30000'])

链接时报

NameError: uninitialized constant MongoReplicaSetClient
    from (irb):3
    from /home/haonan/.rvm/gems/ruby-2.1.4/gems/railties-4.2.3/lib/rails/commands/console.rb:110:in `start'
    from /home/haonan/.rvm/gems/ruby-2.1.4/gems/railties-4.2.3/lib/rails/commands/console.rb:9:in `start'
    from /home/haonan/.rvm/gems/ruby-2.1.4/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:68:in `console'
    from /home/haonan/.rvm/gems/ruby-2.1.4/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
    from /home/haonan/.rvm/gems/ruby-2.1.4/gems/railties-4.2.3/lib/rails/commands.rb:17:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

网上各种查，没找到好的办法，请假大家了