This topic discusses the steps to add a new node to an existing MongoDB replica set.

Prerequisites:
  • An active replica set.
  • A new MongoDB system accessible by the replica set.
  • To add a new member, the MongoDB user must have clusterAdmin privileges.
Note: absrs01 is the name of the replica set used in the following steps.
Complete the following steps to add a node to an existing replica set:
  1. Create the MongoDB directory structure: create mongo, data, logs, and key directory on the new MongoDB node.
    # mkdir -p /opt/pingidentity/mongo/data /opt/pingidentity/mongo/logs \ /opt/pingidentity/mongo/key
  2. Download MongoDB 4.2 on the node and extract to /opt/pingidentity/mongo.
    # cd /opt/pingidentity/ /opt/pingidentity# wget \ https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-rhel70-4.2.0.tgz \ -O mongodb.tgz && tar xzf mongodb.tgz -C /opt/pingidentity/mongo/ --strip-components=1
  3. Update shell path variable and reload the shell.
    /opt/pingidentity# echo PATH=$PATH:/opt/pingidentity/mongo/bin >> ~/.bashrc; /opt/pingidentity# source ~/.bashrc
  4. Copy the contents of the /opt/pingidentity/mongo/key directory from the primary node to the new node into /opt/pingidentity/mongo/key.
  5. Start the MongoDB database on the new node. 
    /opt/pingidentity# cd mongo /opt/pingidentity/mongo# mongod --auth --dbpath ./data/ --logpath ./logs/mongo.log --port 27017 --replSet absrs01 --fork --keyFile ./key/mongodb-keyfile -bind_ip 0.0.0.0
  6. Connect to the mongo shell of the primary node and run the following command.
    absrs01:PRIMARY> rs.add({"host": "<IP address of new node>:27017", "priority": 2})
    Note: On executing step-six, the state of the new node will change to STARTUP2. This indicates that the synchronization between the replica set and the new node has started.
  7. Verify if the new node is added as a Secondary node to the replica set using the following command.
    absrs01:PRIMARY> rs.status()

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