tiup cluster upgrade config check failed

[cyliu0]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

Deploy and start a v4.0.1 cluster with config experimental.allow-auto-random = true
tiup cluster upgrade $cluster_name nightly

tidb has removed the configuration on master.

Workaround: Use cluster edit-config remove the configuration and then upgrade.

2. What did you expect to see?
   Upgrade successfully

3. What did you see instead?
   Upgrade failed because of tidb-server config check failed

4. What version of TiUP are you using (tiup --version)?
   1.0.7

[lonng]

The TiUP won't guarantee all configuration user-configured valid, all configuration will be converted to the toml format directly.

[cyliu0]

How did we deal with a situation like this during the past? The components may abandon some configurations occasionally. And if we do not have a solution for this inside tiup or the components, maybe it will bring a lot of OnCall cases or upgrade document work.

[lonng]

The components have changed the behaviors of treating abandoned configurations, print some warnings instead of panic, this rule can be applied to >= 4.0.2.