rs.addArb()

Description

  • rs.addArb(host)
  • Adds a new arbiter to an existing replica set.

Warning

In general, avoid deploying more than one arbiter per replica set.

The rs.addArb() method takes the following parameter:

ParameterTypeDescriptionhoststringSpecifies the hostname and optionally the port number of the arbitermember to add to replica set.

For the following MongoDB versions, pv1 increases the likelihoodof w:1 rollbacks compared to pv0(no longer supported in MongoDB 4.0+) for replica sets with arbiters:

IP Binding

Starting in MongoDB 3.6, MongoDB binaries, mongod andmongos, bind to localhost by default. If thenet.ipv6 configuration file setting or the —ipv6command line option is set for the binary, the binary additionally bindsto the localhost IPv6 address.

Previously, starting from MongoDB 2.6, only the binaries from theofficial MongoDB RPM (Red Hat, CentOS, Fedora Linux, and derivatives)and DEB (Debian, Ubuntu, and derivatives) packages bind to localhost bydefault.

When bound only to the localhost, these MongoDB 3.6 binaries can onlyaccept connections from clients (including the mongo shell,other members in your deployment for replica sets and sharded clusters)that are running on the same machine. Remote clients cannot connect tothe binaries bound only to localhost.

To override and bind to other ip addresses, you can use thenet.bindIp configuration file setting or the—bind_ip command-line option to specify a list of hostnames or ipaddresses.

Warning

Before binding to a non-localhost (e.g. publicly accessible)IP address, ensure you have secured your cluster from unauthorizedaccess. For a complete list of security recommendations, seeSecurity Checklist. At minimum, considerenabling authentication andhardening network infrastructure.

For example, the following mongod instance binds to boththe localhost and the hostname My-Example-Associated-Hostname, which isassociated with the ip address 198.51.100.1:

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

In order to connect to this instance, remote clients must specifythe hostname or its associated ip address 198.51.100.1:

  1. mongo --host My-Example-Associated-Hostname
  2.  
  3. mongo --host 198.51.100.1

Tip

When possible, use a logical DNS hostname instead of an ip address,particularly when configuring replica set members or sharded clustermembers. The use of logical DNS hostnames avoids configurationchanges due to ip address changes.