Dragonfly

Question: How do you configure replica set member priority in MongoDB?

Answer

In MongoDB, a replica set is a group of mongod instances that maintain the same data set. Replica sets provide redundancy and high availability, and are the basis for all production deployments. Each member of a replica set can have a priority setting which influences both the election for primary and secondary roles within the replica set.

The priority of a replica set member determines its eligibility to become a primary node. Higher priority values increase the likelihood of a member being elected as primary. The priority value can range from 0 to 1000, with most members typically having a default value of 1.

To change the priority of a replica set member, you must reconfigure the replica set with an updated configuration document that specifies the desired priorities.

Here's a step-by-step guideline on how to update the priority of a replica set member:

  1. Connect to the current primary member of your replica set through the mongo shell.
  2. Retrieve the current replica set configuration:

```js
var cfg = rs.conf()
```

  1. Modify the priority value for the desired member(s). In this example, changing the priority of the member with index 1 to 2:

```js
cfg.members[1].priority = 2
```

  1. Apply the new configuration:

```js
rs.reconfig(cfg)
```

Note:

Remember, it's crucial to understand your application's requirements and test any configuration changes in a staging environment before applying them to your production database.

Was this content helpful?

Other Common MongoDB Performance Questions (and Answers)

White Paper

Free System Design on AWS E-Book

Download this early release of O'Reilly's latest cloud infrastructure e-book: System Design on AWS.

Free System Design on AWS E-Book

Switch & save up to 80% 

Dragonfly is fully compatible with the Redis ecosystem and requires no code changes to implement. Instantly experience up to a 25X boost in performance and 80% reduction in cost