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· 7 min read

Introducing Replicasets

The way to achieve fault tolerance in MongoDB is through the use of replica sets.

stateDiagram-v2 [*] --> Application direction LR state Application Application --> replicaset state replicaset { direction RL Primary:primary Secondary1:secondary Secondary2:secondary Secondary1-->Primary : Fetch Oplog Secondary2-->Primary : Fetch Oplog }

Two or more secondary nodes along with a primary node forms a replica set. Application makes all the read/write calls to the primary node which propagate all the write requests synchronously or asynchronously to the secondary nodes.

The Secondary nodes fetches the data via Oplog pull from Primary or other nodes.