Couchbase 4.5 -> 5.1.1 authentication errors

I’m testing an upgrade of a 3 node cluster from community 4.5 to 5.1.1. After upgrading the second node the application started throwing errors about authentication:

2018-09-19 20:12:27.8747 ERROR Couchbase.IO.SharedConnectionPool1[[Couchbase.IO.MultiplexingConnection, Couchbase.NetClient, Version=, Culture=neutral, PublicKeyToken=05e9c6b]] Initialize failed for 4cdcf20f System.Security.Authentication.AuthenticationException: Authentication failed for user 'bucket' at Couchbase.IO.ConnectionPoolBase1.EnableEnhancedAuthentication(IConnection connection) at Couchbase.IO.SharedConnectionPool1.CreateAndAuthConnection() at Couchbase.IO.SharedConnectionPool1.Initialize()

Is this related to the 5.0 RBAC change? My understanding is that it should not enable role based auth until all nodes are upgraded and out of compatibility mode. Is there a way around this? The 4.5 buckets do not use any authentication.

Hi Kadderin,
Thanks for using our Couchbase Server.
I have a quesion. How do you upgrade your cluster? Is it offline or online one? What is the operating system of your cluster? I will try to run upgrade on my centos boxes to reproduce your issue.

Hey Thuan,

This was an online upgrade. The boxes are using CentOS 7.5. I followed the instructions for 5.1.1 to first do a hard-failover on a node (there are no extra nodes available). On the second node I did a swap rebalance with the first to remove it from the cluster and proceeded to upgrade as normal.

Is there any update on this?

For upgrade to 5.1.1 from 4.5, you could do graceful failover and delta recovery to upgrade as mention in this doc
You don’t need hard failover to upgrade. I will try out on my servers and update soon.