Upgrade MongoDB Replica Set to 2.4

MongoDB is the leading NoSQL database, designed for how we build and run applications today. MongoDB empowers organizations to be agile and scalable. It helps them enable new types of applications, improve customer experience, accelerate time to market and reduce total cost of ownership (TCO). MongoDB is named from "huMONGOus" meaning "extremely large".

MongoDB is a general purpose, open-source database. MongoDB features:

• Document data model with dynamic schemas
• Full, flexible index support and rich queries
• Auto-Sharding for horizontal scalability
• Built-in replication for high availability
• Text search
• Advanced security
• Aggregation Framework and MapReduce
• Large media storage with GridFS 

 After having a overview of what Mongodb is,Lets have look on how to upgrade Mongodb to its latest version on Ubuntu.In the general case, the upgrade from MongoDB 2.2 to 2.4 is a binary-compatible “drop-in” upgrade: shut down the mongod instances and replace them with mongod instances running 2.4. However, before you attempt any upgrade please familiarize yourself with the Recommendations and Checklist

When upgrading, consider the following:

• For all deployments using authentication, upgrade the drivers (i.e. client libraries), before upgrading the mongod instance or instances.
• To upgrade to 2.4 sharded clusters must upgrade following the meta-data upgrade procedure.
• If you’re using 2.2.0 and running with auth enabled, you will need to upgrade first to 2.2.1 and then upgrade to 2.4. See Rolling Upgrade Limitation for 2.2.0 Deployments Running with auth Enabled.
•  If you have system.users documents (i.e. for auth) that you created before 2.4 you must ensure that there are no duplicate values for the user field in the system.users collection in any database. If you do have documents with duplicate user fields, you must remove them before upgrading.

 You can upgrade to 2.4 by performing a “rolling” upgrade of the set by upgrading the members individually while the other members are available to minimize downtime. Use the following procedure:

•  Upgrade the secondary members of the set one at a time by shutting down the mongod and replacing the 2.2 binary with the 2.4 binary. After upgrading a mongod instance, wait for the member to recover to SECONDARY state before upgrading the next instance. To check the member’s state, issue rs.status() in the mongo shell.

• Login to one of the secondary in replica set and shutdown the instances. 

                   Akhil@akhil-3450:~# mongo
                         MongoDB shell version: 2.2.3
                         connecting to: test
                         > use admin;                        
                        > db.shutdownServer()

•  Now Install the Lastest package of Mongod

•  Issue the following command to import the 10gen public GPG Key:

                              sudo apt-key adv --keyserver keyserver.ubuntu.com --recv 7F0CEB10

• Create a /etc/apt/sources.list.d/10gen.list file and include the following line for the 10gen repository. 

                             deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen

•  Now issue the following command to reload your repository:

                             sudo apt-get update

• To install a specific release, append the version number to the package name:

                             sudo apt-get install mongodb-10gen=2.X.X

•  To install the latest stable version of MongoDB:

                             sudo apt-get install mongodb-10gen

Once you are done with all the above steps successfully,restart the mongodb and wait for this instances to became secondary and in-sync with the master. 

Now continue upgrading the remaining secondary members by repeating the above steps.After you are done with upgrading secondaries to the latest version It's time to upgrade the master to latest version as well.

• To upgrade master first we need to switch the master,So that one of the Secondary becomes master and the existing master becomes secondary.  

                         Akhil@akhil-3450:~# mongo

                         MongoDB shell version: 2.2.3 

                         connecting to: test

                          > use admin;

                          > rs.StepDown()

•  Once the primary has stepped down and another member has assumed PRIMARY state, as observed in the output of rs.status(),Follow the above mentioned steps for upgrading Secondaries in the replica set.

After all the members of replica set are upgraded to required version,you can switch back the primary and you are done with upgrade of mongodb.

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Written by Unknown

Experience running high-traffic web services, service configuration, monitoring,troubleshooting and change management.Expertise in Linux/Unix system administration, including configuration, troubleshooting, Python scripting language.