rs.add() (original) (raw)

rs.add(host, arbiterOnly)

Adds a member to a replica set. To run the method, you must connect to the primary of the replica set.

rs.add() provides a wrapper around some of the functionality of the replSetReconfig database command and the corresponding mongosh helperrs.reconfig(). See theSelf-Managed Replica Set Configuration document for full documentation of all replica set configuration options.

This method is available in deployments hosted in the following environments:

• MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
• MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

Warning

MongoDB binaries, mongod and mongos, bind to localhost by default. If the net.ipv6 configuration file setting or the --ipv6 command line option is set for the binary, the binary additionally binds to the localhost IPv6 address.

By default mongod and mongos that are bound to localhost only accept connections from clients that are running on the same computer. This binding behavior includesmongosh and other members of your replica set or sharded cluster. Remote clients cannot connect to binaries that are bound only to localhost.

To override the default binding and bind to other IP addresses, use thenet.bindIp configuration file setting or the --bind_ipcommand-line option to specify a list of hostnames or IP addresses.

Warning

For example, the following mongod instance binds to both the localhost and the hostname My-Example-Associated-Hostname, which is associated with the IP address 198.51.100.1:

mongod --bind_ip localhost,My-Example-Associated-Hostname

In order to connect to this instance, remote clients must specify the hostname or its associated IP address 198.51.100.1:

mongosh --host My-Example-Associated-Hostname

mongosh --host 198.51.100.1

Important

To avoid configuration updates due to IP address changes, use DNS hostnames instead of IP addresses. It is particularly important to use a DNS hostname instead of an IP address when configuring replica set members or sharded cluster members.

Use hostnames instead of IP addresses to configure clusters across a split network horizon. Starting in MongoDB 5.0, nodes that are only configured with an IP address fail startup validation and do not start.

rs.add() can, in some cases, trigger an election for primary which will disconnect the shell (such as adding a new member with a higher priority than the current primary). In such cases,mongosh may display an error even if the operation succeeds.

Warning

Before MongoDB 5.0, a newly added secondary still counts as a voting member even though it can neither serve reads nor become primary until its data is consistent. If you are running a MongoDB version earlier than 5.0 and add a secondary with its votesand priority settings greater than zero, this can lead to a case where a majority of the voting members are online but no primary can be elected. To avoid such situations, consider adding the new secondary initially withpriority :0 and votes :0. Then, run rs.status() to ensure the member has transitioned into SECONDARY state. Finally, users.reconfig() to update its priority and votes.

To add a new secondary member with default vote and priority settings to a new replica set, you can call the rs.add() method with:

• Member Configuration Document

rs.add( { host: "mongodbd4.example.net:27017" } )  

• Host name

rs.add( "mongodbd4.example.net:27017" )  

Add a new secondary member with default vote and priority settings to an existing replica set:

rs.add( { host: "mongodbd4.example.net:27017" } )

Warning

Before MongoDB 5.0, a newly added secondary still counts as a voting member even though it can neither serve reads nor become primary until its data is consistent. If you are running a MongoDB version earlier than 5.0 and add a secondary with its votesand priority settings greater than zero, this can lead to a case where a majority of the voting members are online but no primary can be elected. To avoid such situations, consider adding the new secondary initially withpriority :0 and votes :0. Then, run rs.status() to ensure the member has transitioned into SECONDARY state. Finally, users.reconfig() to update its priority and votes.

The following operation adds a mongod instance, running on the host mongodb4.example.net and accessible on the default port27017, as a priority 0secondary member:

rs.add( { host: "mongodbd4.example.net:27017", priority: 0 } )

You must specify the members[n].host field in the member configuration document.

See the members for the available replica set member configuration settings.

The following operation adds a mongod instance, running on the host mongodb3.example.net and accessible on the default port27017 as an arbiter:

• Member Configuration Document

rs.add( { host: "mongodb3.example.net:27017", arbiterOnly: true } )  

• Host name

rs.add("mongodb3.example.net:27017", true)  

See also:

• Add Members to a Self-Managed Replica Set
• Add an Arbiter to a Self-Managed Replica Set
• Replace a Self-Managed Replica Set Member
• Remove Members from a Self-Managed Replica Set