[Other] Discrepancy in upgrade path documentation for 3.13 to 4.3

[elo-magnier-7s]

Community Support Policy

• I have read RabbitMQ's Community Support Policy

RabbitMQ version used

4.2.x

How is RabbitMQ deployed?

RPM package

Steps to reproduce the behavior in question

Hello everyone, me again!

The release of 4.3 has led me to being unable to understand the possible upgrade paths to 4.3.

After some (limited) testing, a standalone node will upgrade in place from 3.13, while a cluster will refuse to do so. As far as I understand what I did, 4.3 reaped mnesia out from under the cluster's feet, so now my cluster is a goner (all good, it's an actual trashable cluster!)

In the upgrade document, it is clearly stated:

It is possible to upgrade RabbitMQ 3.13.x directly to version up to RabbitMQ 4.3.x.

But the table (hidden in "Release Series Upgradeability") doesn't provide any "To" 4.3

In the release notes for the 4.3.0 release in rabbitmq-server state:

Upgrades from earlier series are not supported: users must upgrade to the latest available 4.2.x patch release before upgrading to 4.3.0

and

If your RabbitMQ cluster had plugin rabbitmq_amqp1_0 enabled in RabbitMQ 3.13.x (and your cluster still serves AMQP 1.0 client connections in 4.x), your cluster should do at least one rolling update after enabling feature flag rabbitmq_4.0.0 but before upgrading to 4.3.0.

The first statement implies 3.13 to 4.3 is possible in 1 step, the second says it is not supported, the third that it is possible only if you are not currently running AMQP 1.0 connections.

In total, those 3 statements are not fully contradictory, as it states "possible to" vs "not supported" (although this one says "must upgrade"!), but I believe the statement in this documentation might need to be clarified to reflect the unsupported nature of the operation.

IMHO, the documentation & the second paragraph of the release notes should reflect the verbiage of the first paragraph more, and either specify: "3.13 to 4.3 is not supported, however possible in very limited circumstances", or just say outright that it not possible to do so within support.

Is the 4.3.x in the upgrade documentation a simple typo and should be

It is possible to upgrade RabbitMQ 3.13.x directly to version up to RabbitMQ 4.2.x.
(and optionally) It is possible to upgrade RabbitMQ 4.2.x directly to version RabbitMQ 4.3.x

But then the second paragraph of the release notes doesn't say the upgrade is possible, it says that if you do use AMQP 1.0, you have to step to [4.0-4.2] first, which brings the corollary: If you do not use AMQP 1.0, that step is not needed at all! (also, it's a "should", so optional, and therefore it is possible, which contradicts the "must" in the first paragraph - using the common RFC meanings of both.)

Opening this as a discussion because I'm not sure what the expected result should even be, and I might have messed up my cluster upgrade in some ways.

(Also, just noticed, there's no RabbitMQ 4.3 option in the dropdown on the creste discussion page)

Cheers,
Élodie

[mkuratczyk]

Thanks, we'll review the docs / release notes to make sure they are correct and clear. The short answer is: you have to be on 4.2 to upgrade to 4.3.

[michaelklishin]

Done.

[elo-magnier-7s]

Thank you both!