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Replica sets is the asynchronous master/slave replication added to Mongodb that takes care off all the failover and recovery for the member nodes. According to the mongodb documentation a replicaset is

  • Two or more nodes that are copies of each other
  • Automatic assignment of a primary(master) node if none is available
  • Drivers that automatically detect the new master and send writes to it

More information at Replicasets

Driver usage

To create a new replicaset follow the instructions on the mongodb site to setup the config and the replicaset instances. Then using the driver.

var replSet = new ReplSetServers( [ 
    new Server(, 30000, { auto_reconnect: true } ),
    new Server(, 30001, { auto_reconnect: true } ),
    new Server(, 30002, { auto_reconnect: true } )

var db = new Db('integration_test_', replSet);, p_db) {
  // Do you app stuff :)

The ReplSetSrvers object has the following parameters

var replSet = new ReplSetSrvers(servers, options)


  • servers is an array of Server objects
  • options can contain the following options

Replicaset options

Several options can be passed to the Replicaset constructor with options parameter.

  • rs_name is the name of the replicaset you configured when you started the server, you can have multiple replicasets running on your servers.
  • read_secondary set's the driver to read from secondary servers (slaves) instead of only from the primary(master) server.
  • socketOptions - a collection of pr socket settings

Socket options

Several options can be set for the socketOptions.

  • timeout = set seconds before connection times out default:0
  • noDelay = Disables the Nagle algorithm default:true
  • keepAlive = Set if keepAlive is used default:0, which means no keepAlive, set higher than 0 for keepAlive
  • encoding = 'ascii'|'utf8'|'base64' default:null