Introduction

This chapter aims to get you started with MongoDB replica sets. A replica set is essentially a group of MongoDB servers that form a quorum and replicate data across all nodes. Such a setup not only provides a high availability cluster but also allows the distribution of database reads across multiple nodes. A replica consists of a single primary node along with secondary nodes.

The primary node accepts all writes to the database, and each write operation is replicated to the secondary nodes through replication of operation logs, which are also known as oplogs.

A node is determined as primary by way of an election between the nodes in the replica set. Thus, any node within the cluster can become a primary node at any point. It is important to have an odd number of nodes in the replica set to ensure that the election process does not result in a tie. If you choose to have an even number of nodes in the replica set, MongoDB provides a non-resource intensive arbiter server that can...