One of the most annoying errors is when you don't think you have changed anything and you suddenly see an error!
We have a microservices deployment on Octopus Deploy that points to a MicroK8S cluster on Ubuntu for development and an Azure Kubernetes Service for production. We had deployed successfully on Friday to development but today (the following Thursday), I noticed that it couldn't connect to the dev cluster.
The error in the log was: You must be logged in to the server (the server has asked for the client to provide credentials)
I obviously wondered about credentials expiring (they didn't), changes to the network/firewall (no changes) and then got a bit side-tracked with the fact that client and server versions of K8S need to be close: the client needs to be within 1 minor version above or below the server version. I spent an hour upgrading AKS to 1.17 since the dev cluster is already 1.19 and then downloaded and installed kubectl for 1.18 onto the Octopus but it still didn't work - AKS was fine but the dev cluster was not.
Eventually, after setting up a local cluster config and connecting to the cluster manually (and thank goodness it eventually worked), I realised that something was different on the dev cluster. Instead of username/password, the admin account was now showing as username/token.
I found that by running microk8s config on the dev VM and it prints it in plain text!
Fortunately, Octopus supports tokens so I had to add the named token, updated the connection to the infrastructure and it worked!
I still do not know exactly what has happened but I can only assume that microk8s was updated automatically in the last week and the upgrade must have changed the password to a token, perhaps for security reasons or feature changes, who knows.