Setting up Replica sets in MongoDB
Are you ready to set up replica sets in under 5 minutes? Set your stopwatches. Ready, set, go!
Minute 0: Overview of the servers
We are going to use replica sets consisting of 3 nodes which looks something like this,
Minute 1: Downloading and installing MongoDB
The latest instructions to download and install Mongo can be found here.
For me, running on a CentOS machine, all I had to do was add the 10gen repository, followed by a
install mongo-10gen mongo-10gen-server. To add the 10gen repository, adding the following lines to
[10gen] name=10gen Repository baseurl=http://downloads-distro.mongodb.org/repo/redhat/os/x86_64 gpgcheck=0
$ sudo yum install mongo-10gen mongo-10gen-server
Do this on all your servers.
Minute 2: Editing the configuration file
Next, edit the configuration file which is present at
/etc/mongodb.conf and add the two lines to it
bind_ip = 192.168.1.1 # Public or Internal IP of the server. This will change with each server. replSet = london # This string should be the same on all 3 servers
Again, this should be done on all servers.
Minute 3: Starting Mongo
Start Mongo on all servers by running
$ sudo service mongod start
On Debian systems, you will have to run the mongodb service instead,
$ sudo service mongodb start
Minute 4: Adding nodes to the primary
Pick any machine and enter the Mongo CLI by typing
mongo IP.Of.Server.One. This will be your primary machine (until the cluster decides to elect another as its primary).
rs.initiate() on the machine. This will initialise the node to use replica sets. Then run
rs.add("IP.Of.Server.Three") to add the other two nodes to the replica set.
$ mongo IP.Of.Server.One > rs.initiate(); > rs.add("IP.Of.Server.Two"); > rs.add("IP.Of.Server.Three"); > rs.status();
That's it! We're done. That was easy, wasn't it?
Removing a member of the replica set
Removing a node is as easy as typing