MongoDB Replica Set

How to create Replicate Set in MongoDB using three Ubuntu Virtual Machine

For creating Replica Set we need 3 MongoDB running instance on different or same system.In this example we have taken 3 different ubuntu virtual machine.

Now before we actually see how to make a replica set we need to check the connectivity between all the machine.

So in our case we have three ubuntu machine running on virtual box

1.      All three machine must be able to access the other two machine by SSH. If they cannot they we need to install SSH. We can do that by:

sudo apt-get install openssh-server

2    Next we need to check that all three machine runs on different “Adapter” in Vitual Box .We can check this by opening Virtual Box Window and going to “setting” option for each machine and then to “Network” option and choosing different Adapter for each machine.Also select “Bridged Adapter” in “attached to” option in “Adapter” option for all machine.

3    Now all the three machine should ping each other.

4.   All the three must have different IPs.

Now we are ready to create our Replica Set with three member.

First of all execute under line commands on each of the mongodb instance machine.

sudo nano /etc/mongodb.conf

on executing this a file opens do the following entries in the file

#enable rest

rest =true

adding these lines would turn on REST.Now we move at the bottom of the file and uncomment the replset option and define our replica set name.

replSet = set

Now we save the file.

Now we restart all  the three mongodb instance on different machines.

sudo service mongodb restart

Now on the mongodb instance which we want to make primary open mongodb shell and execute following command

mongo

>rs.initiate()

{
    "info2" : "no configuration explicitly specified -- making one",

    "me" : "dbserver1:27017",
    "info" : "Config now saved locally.  Should come online in about a minute.",
    "ok" : 1
}

Now for adding secondary to the replicate set execute

>rs.add(“ip_of_secondary:port”)

Eg.

 >rs.add(“172.26.32.150:27017”)

    { “ok” : 1 }

Do this for both the secondary mongodb instance machine.

You are done with creation of Replica Set with one primary and two secondary.you can check the status by running command

set:primary>rs.status()

Last and most important thing do not forget to make the entry of each machine ip and hostname in other machines “host file” .Host file is at  /etc/host.