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Remove Members from Replica Set

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To remove a member of a replica set use either of the following procedures.

Remove a Member Using rs.remove()

  1. Shut down the mongod instance for the member you wish to remove. To shut down the instance, connect using mongosh and use the db.shutdownServer() method.

  2. Connect to the replica set's current primary. To determine the current primary, use db.hello() while connected to any member of the replica set.

  3. Use rs.remove() in either of the following forms to remove the member:

    rs.remove("mongod3.example.net:27017")
rs.remove("mongod3.example.net")

    MongoDB may disconnect the shell briefly if the replica set needs to elect a new primary. The shell then automatically reconnects in such cases. The shell may display a DBClientCursor::init call() failed error even though the command succeeds.

Remove a Member Using rs.reconfig()

You can remove a member by reconfiguring the replica set using a replica configuration document where that member is removed from the members array.

Starting in MongoDB 4.4, rs.reconfig() allows adding or removing no more than 1 voting member at a time. To remove multiple voting members from the replica set, issue a series of rs.reconfig() operations to remove one member at a time. See Reconfiguration Can Add or Remove No More than One Voting Member at a Time for more information.

Procedure

  1. Shut down the mongod instance for the member you wish to remove. To shut down the instance, connect using mongosh and use the db.shutdownServer() method.

  2. Connect to the replica set's current primary. To determine the current primary, use db.hello() while connected to any member of the replica set.

  3. Issue the rs.conf() method to view the current configuration document and determine the position in the members array of the member to remove:

    Example

    mongod_C.example.net is in position 2 of the following configuration file:

    {
    "_id" : "rs",
    "version" : 7,
    "members" : [
        {
            "_id" : 0,
            "host" : "mongod_A.example.net:27017"
        },
        {
            "_id" : 1,
            "host" : "mongod_B.example.net:27017"
        },
        {
            "_id" : 2,
            "host" : "mongod_C.example.net:27017"
        }
    ]
}

  4. Assign the current configuration document to the variable cfg:

    cfg = rs.conf()

  5. Modify the cfg object to remove the member.

    Example

    To remove mongod_C.example.net:27017 use the following JavaScript operation:

    cfg.members.splice(2,1)

  6. Overwrite the replica set configuration document with the new configuration by issuing the following:

    rs.reconfig(cfg)

  7. To confirm the new configuration, issue rs.conf().

    For the example above the output would be:

    {
    "_id" : "rs",
    "version" : 8,
    "members" : [
        {
            "_id" : 0,
            "host" : "mongod_A.example.net:27017"
        },
        {
            "_id" : 1,
            "host" : "mongod_B.example.net:27017"
        }
    ]
}