On-Premise Installs: MongoDB Replication

Instructions on setting up a 3 node MongoDB cluster

1. Setup Mongo and Set a Configuration File

In all the 3 servers adjust the configuration file /etc/mongod.conf:

#Select your replication set name
replSet=[replication_set_name]
#Select the replication log size
oplogSize=1024
Disable the bind_ip parameter to avoid binding to only 127.0.0.1 interface
#bind_ip

2. Restart All 3 mongod Daemons

 > sudo service mongod restart

3. Create an Initial Configuration on the Primary

Login to the primary mongo and create an initial configuration. Please notice to use the private IP and not the loopback address (127.0.0.1): 

> mongo
Primary> cfg = {"_id" : "[replication_set_name]", "members" : [{"_id" : 0,"host" : "[Primary_Host_IP]:27017"}]}
Primary> rs.initiate(cfg);

4. Add the Failover Instance to the Replication Set

 Primary> rs.add("[Failover_Host_IP]:27017")

5. Add the Arbier Instance to the Replication Set

 Primary>rs.addArb(":27017")

6. Verify the Replication Set Status

 Primary>rs.status()