MongoMapper-- check that replicas are within a minute of primary

gistfile1.rb

  def all_replicas_in_sync?(verbose=false)
    in_sync = true
    # connect to the primary
    mongo = Mongo::Connection.new(*MongoMapper.connection.primary)
    db = mongo.db('local')
    last_op=db.collection('oplog.rs').find.sort([['$natural',-1]]).limit(1).to_a[0]
    db.collection('slaves').find().to_a.each do |slave|
      opdiff = last_op['ts'].increment - slave['syncedTo'].increment
      diff = (last_op['ts'].seconds - slave['syncedTo'].seconds)/1000.0
      in_sync = false if diff > 60
      if verbose
        puts "#{slave['host']} is #{diff} seconds and #{opdiff} ops behind master (#{in_sync ? 'good' : 'bad'})"
      end
    end
    mongo.close
    return in_sync
  end

Thanks for sharing.