How replication happens in MongoDB?
Replication allows you to increase data availability by creating multiple copies of your data across servers. With MongoDB, replication is achieved through a replica set. Writer operations are sent to the primary server (node), which applies the operations across secondary servers, replicating the data.
What is election in MongoDB?
Replica sets use elections to determine which set member will become primary. Replica sets can trigger an election in response to a variety of events, such as: Adding a new node to the replica set, the secondary members losing connectivity to the primary for more than the configured timeout (10 seconds by default).
How does MongoDB ensure high availability?
How does MongoDB ensure high availability? MongoDB automatically maintains replica sets, multiple copies of data that are distributed across servers, racks and data centers. Replica sets help prevent database downtime using native replication and automatic failover.
How long does it take to set a primary in MongoDB?
The median time before a cluster elects a new primary should not typically exceed 12 seconds, assuming default replica configuration settings. This includes time required to mark the primary as unavailable and call and complete an election .
When does the primary step down in a replica set?
When the primary detects that it can only see a minority of nodes in the replica set, the primary steps down as primary and becomes a secondary. Independently, a member in the partition that can communicate with a majority of the nodes (including itself) holds an election to become the new primary.
What’s the change in MongoDB version 4.0?
Changed in version 4.0: MongoDB 4.0 removes the deprecated replication protocol version 0. Replication protocolVersion: 1 reduces replica set failover time and accelerate the detection of multiple simultaneous primaries.
How to enable retryable writes in MongoDB 4.0?
MongoDB 4.2+ compatible drivers enable retryable writes by default MongoDB 4.0 and 3.6-compatible drivers must explicitly enable retryable writes by including retryWrites=true in the connection string. Changed in version 4.0: MongoDB 4.0 removes the deprecated replication protocol version 0.