Comment 7 for bug 2074309

I was running it directly on the host, but noticed the docker problem when checking, why other services (not rabbitmq) I'm running within an LXD container didn't start.

Your tests might not show the problem, because you've made a fresh install, and rabbitmq-server seems to automatically set flags when the database is newly created. What features had been set in your test environment?

My rabbitmq-installation was running for years and already went through several release upgrades, therefore, none of the feature flags had been set in my database. (Until yesterday, I did not even know that these feature flags exist.)

So testing with a freshly created database might not show the problem.

The best way to deal with the problem would be to put something in the do-release-upgrade script which checks if rabbitmq-server is installed. If not – do nothing, proceed.

But if so, issue a warning text and give the choice to abort or proceed.

In the text, explain, that there is no direct stable upgrade path from 3.9 to 3.12, and that it could be possible under certain circumstances, that the server won't start after upgrade. People should urgently be requested to make a backup of /var/lib/rabbitmq, and make sure to set the recommended flags (or do set it in the upgrade procedure as a third option), and pointed to instructions about what to do if the service does not start after upgrading, or proposed to accept a complete loss and recreate the database from scratch (what could be acceptable in many use cases).

BTW, I just saw that there already are closely related bugs about the same problem: Bug #2038818 and Bug #2046665