upgrade clause for fabric_doc_update

[rnewson]

Overview

acc record introduced in d3eb273

add a clause so an upgraded node can receive a message from a not-yet-upgraded node during a cluster upgrade

Testing recommendations

Confirm doc updates work in a cluster with and without the d3eb273 commit

Related Issues or Pull Requests

#5385
#5371 (#5385 is a prereq)

Checklist

• Code is written and works correctly
• Changes are covered by tests
• Any new configurable parameters are documented in rel/overlay/etc/default.ini
• Documentation changes were made in the src/docs folder
• Documentation changes were backported (separated PR) to affected branches

[rnewson]

questioning myself on the need for this.

[nickva]

This doesn’t quite make sense. We don’t send accumulators across nodes. Is this for a hotpatch perhaps?

[rnewson]

a mixed cluster gets a function_clause in handle_message, and it is thought (by cloudant releng) that the tuple to record change is the culprit. I... don't see how it can be? and my patch here makes no sense either. It would make sense for hot code upgrades, so that in-flight doc updates that were in progress would still work (the module changing between go and handle_message calls).

[rnewson]

we figured this out, it was something else