Initiate the Replica Set

Initiate the replica set to be used for the Event Repository. The replica set is the group of mongod instances that hosts the MATRIXX event-object data set in your MongoDB system.

Before you begin

Before initiating the replica set, verify the following in the MongoDB configuration file:
  • Verify that the replication option is set to MtxEventReplSet.
  • Verify that the authorization option is set to enabled.
  • Verify that all mongod instances on each of the MongoDB host servers are started.
Important: In MongoDB 4.0, you cannot specify the --nojournal option or storage.journal.enabled: false for replica set members that use the WiredTiger storage engine. Refer to the MongoDB product documentation for compatibility changes in MongoDB 4.0.

Verify that each member of the replica set is accessible using a resolvable DNS or host name. Either configure your DNS names appropriately or set up your systems' /etc/hosts file to reflect this configuration. For more information, see the MongoDB documentation.

About this task

The instructions in this procedure initiates a single replica set with three mongod instances.

Procedure

  1. Connect to one of the mongod instances locally.
  2. Using the MongoDB mongo shell CLI, enter the rs.initiate() command to initiate the replica set:
    mongo
    rs.initiate({
    "_id" : "MtxEventReplSet",
    "members" : [
    {"_id" : 0, "host" : "ip1", "arbiterOnly": false},
    {"_id" : 1, "host" : "ip2", "arbiterOnly": false},
    {"_id" : 2, "host" : "ip3", "arbiterOnly": false}
    ]
    })
    where:
    • ip1, ip2, and ip3 are the hostnames (or IP addresses) and port numbers of the host servers where mongod instances of the replica set are to run. The port number is required only if the port number is not the default (27017).
    • The arbiterOnly option is set to true if the mongod instance is to run as an arbiter only.

    For example: 

    mongo --host 192.0.2.0
 rs.initiate({
    "_id" : "MtxEventReplSet",
    "members" : [
        {"_id" : 0, "host" : "dbhost01", "arbiterOnly": false},
        {"_id" : 1, "host" : "10.10.10.2", "arbiterOnly": false},
        {"_id" : 2, "host" : "dbhost033:27020", "arbiterOnly": true}
    ]
})
{ "ok" : 1 }
  3. Identify the replica set primary (mongod primary) by issuing the mongo shell CLI command rs.status() on any server.

    A few seconds after the replica set is initialized, one mongod instance is elected as the primary of the replica set. All changes to the replica set must be done when connected to the primary from this point in the setup instructions.

What to do next

Now that the replica set is initialized, create replica set users. You must be connected to the replica set primary to create the users.