{"id":49613,"date":"2019-02-17T09:50:37","date_gmt":"2019-02-17T04:20:37","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=49613"},"modified":"2021-05-09T13:07:14","modified_gmt":"2021-05-09T07:37:14","slug":"mongodb-replication-and-sharding","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/mongodb-replication-and-sharding\/","title":{"rendered":"MongoDB Replication – 2 Major Strategies of Sharding in MongoDB"},"content":{"rendered":"

After studying MongoDB Aggregation<\/strong>, it’s time to learn MongoDB Replication and Sharding. Replication\u00a0instances that maintain the same data set and MongoDB Sharding consists of 3 parts.<\/p>\n

Here, we will explore how to set up a replica set, MongoDB Sharded, and Non-Sharded Collections with their workings.<\/p>\n

So, are you ready to explore MongoDB Replication and Sharding?<\/p>\n

What is MongoDB Replication?<\/h2>\n

As the name says, MongoDB replication means instances that maintain the same data set<\/em>. It contains several data bearing nodes and optionally one arbiter node.<\/p>\n

Out of all the data bearing nodes, only one of them is a primary node while the others are secondary nodes. A primary node can do all the write operations. A replica set containing primary node is can confirm writes with {w: \u201cmajority\u201d}.<\/p>\n

\"MongoDB<\/a><\/p>\n

The secondary nodes replicate the primary one and apply the operations to their respective dataset. When the data is reflected in the second one it also changes on the primary dataset. If the primary node is not available then the secondary nodes from themselves can elect one of them as a primary node.<\/p>\n

\"Primary<\/a><\/p>\n

Here arbiters do not have a dataset with themselves. Its purpose is to maintain a quorum in a replica set by responding to heartbeat and election requests by other replica members. If your replica set has an even number of members, add an arbiter to obtain a majority of votes in an election for a primary node.<\/p>\n

\"Second<\/a><\/p>\n

Automatic Failover<\/h2>\n

When a primary node does not communicate with other members of the set for a certain period of time i.e. electionTimeoutMills(10 seconds by default) period,<\/em> then an eligible secondary node calls out for an election.<\/p>\n

The clusters present over here try to complete the election as fast as possible so that they can return to the normal operations to be performed.<\/p>\n

\"Automatic<\/a><\/p>\n

Here, the replica set cannot process write operation until the election is completed.<\/p>\n

How to Set Up a Replica Set in MongoDB?<\/h2>\n

Here, we will learn how to convert a standalone MongoDB instance to the replica set. Following are the steps to convert:<\/p>\n