Replica set is a term, used for defining a DB cluster of multiple nodes inclusion, with the master-slave replication and an automated failover set between them. Such a structure usually requires an uneven number of members to ensure the correct primary (master) database’ election. This selected DB will process all the incoming write operations, storing the information about them within its oplog, where they can be accessed and replicated by every secondary (slave) replica member for being applied to their data sets. In such a way, all of the servers will represent the same content and ensure its availability.
In case some unexpected issue occurs, causing the primary database downtime (e.g. due to hardware failure or connection interruption), a new election process will be initiated automatically, helping to restore the normal application functioning, without any manual intervention required. In such a way, replica set inherits the benefits of usual replication (like failover redundancy, increased data availability and read capacity, disaster recovery, etc) and simultaneously eliminates the complexity of managing numerous databases separately.Thus, here is a simple instruction, that will show you how to create and configure a MongoDB replica set with three members - such a complexion is considered to ensure enough margin of information safety and sufficient out-turn to handle the required amount of I/O operations, for most of the commonly used applications. So, proceed with performing the instructions in the following sections one-by-one:
And once your replica set is ready, you are able to easily make sure everything is configured properly using the DB Cluster Availability Check-Up part of this tutorial.