Replica sets that have two members do not fail over properly because if a member goes down, a new master cannot be elected.

repl_set_connection.rb has examples of two member replica sets in it's documentation.

1. @example Connect to a replica set and provide two seed nodes:
2. ReplSetConnection.new(['localhost', 30000], ['localhost', 30001])
   #
3. @example Connect to a replica set providing two seed nodes and ensuring a connection to the replica set named 'prod':
4. ReplSetConnection.new(['localhost', 30000], ['localhost', 30001], :rs_name => 'prod')
   #
5. @example Connect to a replica set providing two seed nodes and allowing reads from a secondary node:
6. ReplSetConnection.new(['localhost', 30000], ['localhost', 30001], :read_secondary => true)

This is an unsafe setup. Please provide a safe setup and note it in the docs.