- Okay, welcome back, in this demo, I'm going to show you how to initialize the MongoDB replicaset and then populate it with data. Establishing and configuring a replicaset gives us a layer of data redundancy which is always helpful in production systems since each and every data write to the MongoDB primary will then be replicated to both MongoDB secondaries within the replicaset. Okay, let's begin, let's jump back into the runsheet and this time copy the first code block from Step 13. I'll use this to write out a configuration file into our local directory. 

A couple things to highlight before we execute it. Firstly, we are configuring the replicaset to use the stable DNS network names that I highlighted and walked you through in the previous demonstration. This is a key requirement to allow the underlying pods to float across the cluster worker nodes should the cluster orchestrator decide to reschedule and relaunch them on differing nodes. The replicaset configuration has a 5 second pause included to ensure that MongoDB has enough time to perform the replicaset management before we go and attempt to use it. This is merely a precaution to enough time to the MongoDB Replicaset to reorganize itself.

Okay, we are ready to execute it now. I'll jump back into the runsheet and copy the following command which will establish a remote shell connection to the first Mongo pod and execute the Mongo client on it passing in the contents of the db.init file. Ignoring the warning about not being able to save history, everything looks good and the MongoDB replicaset has been established successfully. Let's confirm this by running the following command rs.status *​ Here we can see that Mongo-1 and Mongo-2 have been registered as the secondaries, and Mongo-0 has been registered as the primary. 

This looks good and the database is ready to be populated. Let's do this now, jumping back into the runsheet, copy the database population script and run it within the terminal. Again, this will create a new script file on the file system in the current local directory. I'll now copy and run the next command which will actually connect to the MongoDB database and populate it using the same technique as used to configure the replicaset. Okay, finally execute the last command within Step 14 to test that indeed we have successfully populated it with documents one per programming language with their respective votes counterset to zero. Brilliant, that looks good. 

Okay, that completes Steps 13 and 14. We've now successfully populated our MongoDB database and we are all good to go. That concludes this demo We're now ready to setup and deploy the API which will connect against our MongoDB database and perform read and writes against it.