Document downgrade procedure (if supported)

[zamazan4ik]

Summary
After reading the section about Upgrade procedure it's not clear - is the downgrade process supported or not? E.g. during the update, I found an issue with the newer version, and I want to fall back to the previous version. Could I do it? Could I do it without downtime?

[Xuanwo]

is the downgrade process supported or not?

No, we don't support downgrade at this stage.

However, if no data has been written, we can switch to old versions by replacing the binary directly.

[zamazan4ik]

Could you please mention it explicitly in the documentation? Since this information will be written explicitly, system administrators will plan other ways for possible mitigations during the unsuccessful upgrade process (test before on a separate cluster, blue-green deploys with multiple clusters, etc.).

[BohuTANG]

E.g. during the update, I found an issue with the newer version, and I want to fall back to the previous version. Could I do it? Could I do it without downtime?

During the update falling back to the previous version is OK.

This does not usually happen, and we generally do not change the underlying data format to cause incompatibilities, but problems may arise with two versions that span a wide range.

[zamazan4ik]

So at least during the update, if something goes wrong, the downgrade is supported? Do you write explicitly in the release notes, if the underlying data format changes incompatibly in a new version?

[BohuTANG]

Thanks.

We will improve the documentation, and if a breaking change occurs in a future version, we will make special instructions and tell users how to do the upgrade.