How to update Couchbase Server from 3.0 to 4.0?

I have query about Couchbase Server updation to latest version. How to update my existing Server version to latest version without any Server Down Time.

To avoid server downtime, you need to do a rolling upgrade. Take a look at our different strategies:

@ldoguin Thanks for quick reply.

When I try to do that to upgrade Couchbase 3.x to 4.1.1 I get an error: Attention - Node attempting to join an older cluster. Some of the selected services are not available.

How do you do a rolling swap rebalance of 3.x to 4.x?