Yes, the IBP is used a gate for certain features.
Once you have brokers in your cluster using it, they might respond to requests
using that version that require writing new formats to disk (among other
behaviours).
If you were then to introduce a broker that is using an older binary (through a
downgrade of an existing node or by spinning up a new node with an older binary
version) that older version may not understand this new feature/message when it
sees it and would fail.
That is why you should first upgrade all the brokers in you cluster to the new
binary version but with the old IBP version (and LMF version for older kafka
versions) and then establish that everything is running smoothly and that all
your client applications are happy **before** you upgrade the IBP.
Tom Cooper
@tomncooper | tomcooper.dev
--- Original Message ---
On Thursday, December 15th, 2022 at 08:33, Swathi Mocharla
wrote:
> Hello,
> In the upgrade docs, it is mentioned "Restart the brokers one by one for
> the new protocol version to take effect. Once the brokers begin using the
> latest protocol version, it will no longer be possible to downgrade the
> cluster to an older version."
>
> What does this mean? Is this statement applicable to every version other
> than 2.1 as well? Does that mean after the update of the inter broker
> protocol, one should not rollback to a prior version?
>
> Thanks,
> Swathi
